update all examples to use unique ID as serial if avaialble

23 files changed, 916 insertions, 653 deletions

diff --git a/examples/device/audio_4_channel_mic/src/usb_descriptors.c b/examples/device/audio_4_channel_mic/src/usb_descriptors.c
index b77da9fac..728a5f9ce 100644
--- a/examples/device/audio_4_channel_mic/src/usb_descriptors.c
+++ b/examples/device/audio_4_channel_mic/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -116,50 +117,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
-{
-    (const char[]) { 0x09, 0x04 }, 	// 0: is supported language is English (0x0409)
-    "PaniRCorp",                   	// 1: Manufacturer
-    "MicNode_4_Ch",    		// 2: Product
-    "123458",                      	// 3: Serials, should use chip ID
-    "UAC2",                 	 	// 4: Audio Interface
+char const* string_desc_arr [] = {
+    (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
+    "PaniRCorp",                   // 1: Manufacturer
+    "MicNode_4_Ch",                // 2: Product
+    NULL,                          // 3: Serials will use unique ID if possible
+    "UAC2",                        // 4: Audio Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Convert ASCII string into UTF-16
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/audio_test/src/usb_descriptors.c b/examples/device/audio_test/src/usb_descriptors.c
index cc364ee88..9864377f6 100644
--- a/examples/device/audio_test/src/usb_descriptors.c
+++ b/examples/device/audio_test/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -116,50 +117,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
 char const* string_desc_arr [] =
 {
-    (const char[]) { 0x09, 0x04 }, 	// 0: is supported language is English (0x0409)
-    "PaniRCorp",                   	// 1: Manufacturer
-    "MicNode",              		// 2: Product
-    "123456",                      	// 3: Serials, should use chip ID
-    "UAC2",                 	 	// 4: Audio Interface
+    (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
+    "PaniRCorp",                   // 1: Manufacturer
+    "MicNode",                     // 2: Product
+    NULL,                          // 3: Serials will use unique ID if possible
+    "UAC2",                        // 4: Audio Interface
+
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Convert ASCII string into UTF-16
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/audio_test_multi_rate/src/usb_descriptors.c b/examples/device/audio_test_multi_rate/src/usb_descriptors.c
index 2c72edb17..f50e70a25 100644
--- a/examples/device/audio_test_multi_rate/src/usb_descriptors.c
+++ b/examples/device/audio_test_multi_rate/src/usb_descriptors.c
@@ -24,6 +24,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -120,50 +121,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
 char const* string_desc_arr [] =
 {
-    (const char[]) { 0x09, 0x04 }, 	// 0: is supported language is English (0x0409)
-    "PaniRCorp",                   	// 1: Manufacturer
-    "MicNode",              		// 2: Product
-    "123456",                      	// 3: Serials, should use chip ID
-    "UAC2",                 	 	// 4: Audio Interface
+    (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
+    "PaniRCorp",                   // 1: Manufacturer
+    "MicNode",                     // 2: Product
+    NULL,                          // 3: Serials will use unique ID if possible
+    "UAC2",                        // 4: Audio Interface
+
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Convert ASCII string into UTF-16
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/cdc_dual_ports/src/usb_descriptors.c b/examples/device/cdc_dual_ports/src/usb_descriptors.c
index 8be404cc9..de2505c07 100644
--- a/examples/device/cdc_dual_ports/src/usb_descriptors.c
+++ b/examples/device/cdc_dual_ports/src/usb_descriptors.c
@@ -23,13 +23,14 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
  * Same VID/PID with different interface e.g MSC (first), then CDC (later) will possibly cause system error on PC.
  *
  * Auto ProductID layout's Bitmap:
- *   [MSB]       MIDI | HID | MSC | CDC          [LSB]
+ *   [MSB]         HID | MSC | CDC          [LSB]
  */
 #define _PID_MAP(itf, n)  ( (CFG_TUD_##itf) << (n) )
 #define USB_PID           (0x4000 | _PID_MAP(CDC, 0) | _PID_MAP(MSC, 1) | _PID_MAP(HID, 2) | \
@@ -213,52 +214,64 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB CDC",                 // 4: CDC Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/cdc_msc/src/usb_descriptors.c b/examples/device/cdc_msc/src/usb_descriptors.c
index baf919f84..2afa24903 100644
--- a/examples/device/cdc_msc/src/usb_descriptors.c
+++ b/examples/device/cdc_msc/src/usb_descriptors.c
@@ -42,35 +42,33 @@
 //--------------------------------------------------------------------+
 // Device Descriptors
 //--------------------------------------------------------------------+
-tusb_desc_device_t const desc_device =
-{
-  .bLength            = sizeof(tusb_desc_device_t),
-  .bDescriptorType    = TUSB_DESC_DEVICE,
-  .bcdUSB             = USB_BCD,
+tusb_desc_device_t const desc_device = {
+    .bLength            = sizeof(tusb_desc_device_t),
+    .bDescriptorType    = TUSB_DESC_DEVICE,
+    .bcdUSB             = USB_BCD,
 
-  // Use Interface Association Descriptor (IAD) for CDC
-  // As required by USB Specs IAD's subclass must be common class (2) and protocol must be IAD (1)
-  .bDeviceClass       = TUSB_CLASS_MISC,
-  .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
-  .bDeviceProtocol    = MISC_PROTOCOL_IAD,
+    // Use Interface Association Descriptor (IAD) for CDC
+    // As required by USB Specs IAD's subclass must be common class (2) and protocol must be IAD (1)
+    .bDeviceClass       = TUSB_CLASS_MISC,
+    .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
+    .bDeviceProtocol    = MISC_PROTOCOL_IAD,
 
-  .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
+    .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
 
-  .idVendor           = USB_VID,
-  .idProduct          = USB_PID,
-  .bcdDevice          = 0x0100,
+    .idVendor           = USB_VID,
+    .idProduct          = USB_PID,
+    .bcdDevice          = 0x0100,
 
-  .iManufacturer      = 0x01,
-  .iProduct           = 0x02,
-  .iSerialNumber      = 0x03,
+    .iManufacturer      = 0x01,
+    .iProduct           = 0x02,
+    .iSerialNumber      = 0x03,
 
-  .bNumConfigurations = 0x01
+    .bNumConfigurations = 0x01
 };
 
 // Invoked when received GET DEVICE DESCRIPTOR
 // Application return pointer to descriptor
-uint8_t const * tud_descriptor_device_cb(void)
-{
+uint8_t const *tud_descriptor_device_cb(void) {
   return (uint8_t const *) &desc_device;
 }
 
@@ -78,8 +76,7 @@ uint8_t const * tud_descriptor_device_cb(void)
 // Configuration Descriptor
 //--------------------------------------------------------------------+
 
-enum
-{
+enum {
   ITF_NUM_CDC = 0,
   ITF_NUM_CDC_DATA,
   ITF_NUM_MSC,
@@ -96,7 +93,7 @@ enum
   #define EPNUM_MSC_OUT     0x05
   #define EPNUM_MSC_IN      0x85
 
-#elif CFG_TUSB_MCU == OPT_MCU_SAMG  || CFG_TUSB_MCU ==  OPT_MCU_SAMX7X
+#elif CFG_TUSB_MCU == OPT_MCU_SAMG || CFG_TUSB_MCU == OPT_MCU_SAMX7X
   // SAMG & SAME70 don't support a same endpoint number with different direction IN and OUT
   //    e.g EP1 OUT & EP1 IN cannot exist together
   #define EPNUM_CDC_NOTIF   0x81
@@ -141,67 +138,62 @@ enum
 #define CONFIG_TOTAL_LEN    (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + TUD_MSC_DESC_LEN)
 
 // full speed configuration
-uint8_t const desc_fs_configuration[] =
-{
-  // Config number, interface count, string index, total length, attribute, power in mA
-  TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),
+uint8_t const desc_fs_configuration[] = {
+    // Config number, interface count, string index, total length, attribute, power in mA
+    TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),
 
-  // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
-  TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 64),
+    // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
+    TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 64),
 
-  // Interface number, string index, EP Out & EP In address, EP size
-  TUD_MSC_DESCRIPTOR(ITF_NUM_MSC, 5, EPNUM_MSC_OUT, EPNUM_MSC_IN, 64),
+    // Interface number, string index, EP Out & EP In address, EP size
+    TUD_MSC_DESCRIPTOR(ITF_NUM_MSC, 5, EPNUM_MSC_OUT, EPNUM_MSC_IN, 64),
 };
 
 #if TUD_OPT_HIGH_SPEED
 // Per USB specs: high speed capable device must report device_qualifier and other_speed_configuration
 
 // high speed configuration
-uint8_t const desc_hs_configuration[] =
-{
-  // Config number, interface count, string index, total length, attribute, power in mA
-  TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),
+uint8_t const desc_hs_configuration[] = {
+    // Config number, interface count, string index, total length, attribute, power in mA
+    TUD_CONFIG_DESCRIPTOR(1, ITF_NUM_TOTAL, 0, CONFIG_TOTAL_LEN, 0x00, 100),
 
-  // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
-  TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 512),
+    // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
+    TUD_CDC_DESCRIPTOR(ITF_NUM_CDC, 4, EPNUM_CDC_NOTIF, 8, EPNUM_CDC_OUT, EPNUM_CDC_IN, 512),
 
-  // Interface number, string index, EP Out & EP In address, EP size
-  TUD_MSC_DESCRIPTOR(ITF_NUM_MSC, 5, EPNUM_MSC_OUT, EPNUM_MSC_IN, 512),
+    // Interface number, string index, EP Out & EP In address, EP size
+    TUD_MSC_DESCRIPTOR(ITF_NUM_MSC, 5, EPNUM_MSC_OUT, EPNUM_MSC_IN, 512),
 };
 
 // other speed configuration
 uint8_t desc_other_speed_config[CONFIG_TOTAL_LEN];
 
 // device qualifier is mostly similar to device descriptor since we don't change configuration based on speed
-tusb_desc_device_qualifier_t const desc_device_qualifier =
-{
-  .bLength            = sizeof(tusb_desc_device_qualifier_t),
-  .bDescriptorType    = TUSB_DESC_DEVICE_QUALIFIER,
-  .bcdUSB             = USB_BCD,
+tusb_desc_device_qualifier_t const desc_device_qualifier = {
+    .bLength            = sizeof(tusb_desc_device_qualifier_t),
+    .bDescriptorType    = TUSB_DESC_DEVICE_QUALIFIER,
+    .bcdUSB             = USB_BCD,
 
-  .bDeviceClass       = TUSB_CLASS_MISC,
-  .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
-  .bDeviceProtocol    = MISC_PROTOCOL_IAD,
+    .bDeviceClass       = TUSB_CLASS_MISC,
+    .bDeviceSubClass    = MISC_SUBCLASS_COMMON,
+    .bDeviceProtocol    = MISC_PROTOCOL_IAD,
 
-  .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
-  .bNumConfigurations = 0x01,
-  .bReserved          = 0x00
+    .bMaxPacketSize0    = CFG_TUD_ENDPOINT0_SIZE,
+    .bNumConfigurations = 0x01,
+    .bReserved          = 0x00
 };
 
 // Invoked when received GET DEVICE QUALIFIER DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete.
 // device_qualifier descriptor describes information about a high-speed capable device that would
 // change if the device were operating at the other speed. If not highspeed capable stall this request.
-uint8_t const* tud_descriptor_device_qualifier_cb(void)
-{
-  return (uint8_t const*) &desc_device_qualifier;
+uint8_t const *tud_descriptor_device_qualifier_cb(void) {
+  return (uint8_t const *) &desc_device_qualifier;
 }
 
 // Invoked when received GET OTHER SEED CONFIGURATION DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
 // Configuration descriptor in the other speed e.g if high speed then this is for full speed and vice versa
-uint8_t const* tud_descriptor_other_speed_configuration_cb(uint8_t index)
-{
+uint8_t const *tud_descriptor_other_speed_configuration_cb(uint8_t index) {
   (void) index; // for multiple configurations
 
   // if link speed is high return fullspeed config, and vice versa
@@ -221,13 +213,12 @@ uint8_t const* tud_descriptor_other_speed_configuration_cb(uint8_t index)
 // Invoked when received GET CONFIGURATION DESCRIPTOR
 // Application return pointer to descriptor
 // Descriptor contents must exist long enough for transfer to complete
-uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
-{
+uint8_t const *tud_descriptor_configuration_cb(uint8_t index) {
   (void) index; // for multiple configurations
 
 #if TUD_OPT_HIGH_SPEED
   // Although we are highspeed, host may be fullspeed.
-  return (tud_speed_get() == TUSB_SPEED_HIGH) ?  desc_hs_configuration : desc_fs_configuration;
+  return (tud_speed_get() == TUSB_SPEED_HIGH) ? desc_hs_configuration : desc_fs_configuration;
 #else
   return desc_fs_configuration;
 #endif
@@ -246,57 +237,55 @@ enum {
 };
 
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
-{
-  (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
-  "TinyUSB",                     // 1: Manufacturer
-  "TinyUSB Device",              // 2: Product
-  "123456789012",                // 3: Serials, should use chip ID
-  "TinyUSB CDC",                 // 4: CDC Interface
-  "TinyUSB MSC",                 // 5: MSC Interface
+char const *string_desc_arr[] = {
+    (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
+    "TinyUSB",                     // 1: Manufacturer
+    "TinyUSB Device",              // 2: Product
+    NULL,                          // 3: Serials will use unique ID if possible
+    "TinyUSB CDC",                 // 4: CDC Interface
+    "TinyUSB MSC",                 // 5: MSC Interface
 };
 
-static uint16_t _desc_str[32+1];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
-
   size_t chr_count;
 
-  switch(index) {
+  switch ( index ) {
     case STRID_LANGID:
       memcpy(&_desc_str[1], string_desc_arr[0], 2);
       chr_count = 1;
       break;
 
     case STRID_SERIAL:
-      chr_count = board_usb_get_serial(_desc_str+1, 32);
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
       break;
 
     default:
       // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
       // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-      if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-      const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
       // Cap at max char
       chr_count = strlen(str);
-      if ( chr_count > 31 ) chr_count = 31;
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
       // Convert ASCII string into UTF-16
-      for(size_t i=0; i<chr_count; i++) {
-        _desc_str[1+i] = str[i];
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
       }
       break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/cdc_msc_freertos/src/usb_descriptors.c b/examples/device/cdc_msc_freertos/src/usb_descriptors.c
index 822442724..9c29701c7 100644
--- a/examples/device/cdc_msc_freertos/src/usb_descriptors.c
+++ b/examples/device/cdc_msc_freertos/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -212,53 +213,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456789012",                // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB CDC",                 // 4: CDC Interface
   "TinyUSB MSC",                 // 5: MSC Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/cdc_uac2/src/usb_descriptors.c b/examples/device/cdc_uac2/src/usb_descriptors.c
index 58b711978..72a695622 100644
--- a/examples/device/cdc_uac2/src/usb_descriptors.c
+++ b/examples/device/cdc_uac2/src/usb_descriptors.c
@@ -25,6 +25,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -150,53 +151,66 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 },  // 0: is supported language is English (0x0409)
   "TinyUSB",                      // 1: Manufacturer
   "TinyUSB headset",              // 2: Product
-  "000001",                       // 3: Serials, should use chip ID
+  NULL,                           // 3: Serials will use unique ID if possible
   "TinyUSB Speakers",             // 4: Audio Interface
   "TinyUSB Microphone",           // 5: Audio Interface
   "TinyUSB CDC",                  // 6: Audio Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
-  (void)langid;
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
+  (void) langid;
+  size_t chr_count;
 
-  uint8_t chr_count;
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  if (index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }
-  else
-  {
-    // Convert ASCII string into UTF-16
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if (!(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0]))) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if (chr_count > 31) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    for (uint8_t i = 0; i < chr_count; i++)
-    {
-      _desc_str[1 + i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/dfu/src/usb_descriptors.c b/examples/device/dfu/src/usb_descriptors.c
index 51a0d09f5..fd469aaf2 100644
--- a/examples/device/dfu/src/usb_descriptors.c
+++ b/examples/device/dfu/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "class/dfu/dfu_device.h"
 
@@ -116,56 +117,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "FLASH",                       // 4: DFU Partition 1
   "EEPROM",                      // 5: DFU Partition 2
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
-
   size_t chr_count;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }
-  else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
+
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) {
-      chr_count = 31;
-    }
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t)((((uint16_t)TUSB_DESC_STRING) << 8 ) | (2u*chr_count + 2u));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/dfu_runtime/src/usb_descriptors.c b/examples/device/dfu_runtime/src/usb_descriptors.c
index 1b0a60551..7ac53d255 100644
--- a/examples/device/dfu_runtime/src/usb_descriptors.c
+++ b/examples/device/dfu_runtime/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "class/dfu/dfu_rt_device.h"
 
@@ -112,55 +113,64 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB DFU runtime",         // 4: DFU runtime
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
-
   size_t chr_count;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }
-  else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
+
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) {
-      chr_count = 31;
-    }
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/dynamic_configuration/src/usb_descriptors.c b/examples/device/dynamic_configuration/src/usb_descriptors.c
index 039c7636c..7f35b4b22 100644
--- a/examples/device/dynamic_configuration/src/usb_descriptors.c
+++ b/examples/device/dynamic_configuration/src/usb_descriptors.c
@@ -23,8 +23,8 @@
  *
  */
 
-#include "tusb.h"
 #include "bsp/board_api.h"
+#include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
  * Same VID/PID with different interface e.g MSC (first), then CDC (later) will possibly cause system error on PC.
@@ -206,51 +206,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/hid_boot_interface/src/usb_descriptors.c b/examples/device/hid_boot_interface/src/usb_descriptors.c
index 10345ab41..d68ef16d9 100644
--- a/examples/device/hid_boot_interface/src/usb_descriptors.c
+++ b/examples/device/hid_boot_interface/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -130,51 +131,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/hid_composite/src/usb_descriptors.c b/examples/device/hid_composite/src/usb_descriptors.c
index 347bbf29a..e174db46d 100644
--- a/examples/device/hid_composite/src/usb_descriptors.c
+++ b/examples/device/hid_composite/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -177,51 +178,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/hid_composite_freertos/src/usb_descriptors.c b/examples/device/hid_composite_freertos/src/usb_descriptors.c
index 30f327d5e..85820de55 100644
--- a/examples/device/hid_composite_freertos/src/usb_descriptors.c
+++ b/examples/device/hid_composite_freertos/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -175,51 +176,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/hid_generic_inout/src/usb_descriptors.c b/examples/device/hid_generic_inout/src/usb_descriptors.c
index 8377a0f47..64f6d17ae 100644
--- a/examples/device/hid_generic_inout/src/usb_descriptors.c
+++ b/examples/device/hid_generic_inout/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -120,51 +121,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/hid_multiple_interface/src/usb_descriptors.c b/examples/device/hid_multiple_interface/src/usb_descriptors.c
index 42471a961..86f567e8e 100644
--- a/examples/device/hid_multiple_interface/src/usb_descriptors.c
+++ b/examples/device/hid_multiple_interface/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -136,53 +137,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 },  // 0: is supported language is English (0x0409)
   "TinyUSB",                      // 1: Manufacturer
   "TinyUSB Device",               // 2: Product
-  "123456",                       // 3: Serials, should use chip ID
+  NULL,                           // 3: Serials will use unique ID if possible
   "Keyboard Interface",           // 4: Interface 1 String
   "Mouse Interface",              // 5: Interface 2 String
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
 
-  uint8_t chr_count;
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/midi_test/src/usb_descriptors.c b/examples/device/midi_test/src/usb_descriptors.c
index 4845dcf57..9781d3d6f 100644
--- a/examples/device/midi_test/src/usb_descriptors.c
+++ b/examples/device/midi_test/src/usb_descriptors.c
@@ -23,13 +23,14 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
  * Same VID/PID with different interface e.g MSC (first), then CDC (later) will possibly cause system error on PC.
  *
  * Auto ProductID layout's Bitmap:
- *   [MSB]       MIDI | HID | MSC | CDC          [LSB]
+ *   [MSB]         HID | MSC | CDC          [LSB]
  */
 #define _PID_MAP(itf, n)  ( (CFG_TUD_##itf) << (n) )
 #define USB_PID           (0x4000 | _PID_MAP(CDC, 0) | _PID_MAP(MSC, 1) | _PID_MAP(HID, 2) | \
@@ -133,51 +134,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/msc_dual_lun/src/usb_descriptors.c b/examples/device/msc_dual_lun/src/usb_descriptors.c
index 2de81111c..c0610945f 100644
--- a/examples/device/msc_dual_lun/src/usb_descriptors.c
+++ b/examples/device/msc_dual_lun/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -141,51 +142,63 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456789012",                // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/net_lwip_webserver/src/usb_descriptors.c b/examples/device/net_lwip_webserver/src/usb_descriptors.c
index 3c0ed3db7..da628c8be 100644
--- a/examples/device/net_lwip_webserver/src/usb_descriptors.c
+++ b/examples/device/net_lwip_webserver/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -190,55 +191,56 @@ static char const* string_desc_arr [] =
   [STRID_LANGID]       = (const char[]) { 0x09, 0x04 }, // supported language is English (0x0409)
   [STRID_MANUFACTURER] = "TinyUSB",                     // Manufacturer
   [STRID_PRODUCT]      = "TinyUSB Device",              // Product
-  [STRID_SERIAL]       = "123456",                      // Serial
+  [STRID_SERIAL]       = NULL,                          // Serials will use unique ID if possible
   [STRID_INTERFACE]    = "TinyUSB Network Interface"    // Interface Description
 
   // STRID_MAC index is handled separately
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
-
   unsigned int chr_count = 0;
 
-  if (STRID_LANGID == index)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[STRID_LANGID], 2);
-    chr_count = 1;
-  }
-  else if (STRID_MAC == index)
-  {
-    // Convert MAC address into UTF-16
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-    for (unsigned i=0; i<sizeof(tud_network_mac_address); i++)
-    {
-      _desc_str[1+chr_count++] = "0123456789ABCDEF"[(tud_network_mac_address[i] >> 4) & 0xf];
-      _desc_str[1+chr_count++] = "0123456789ABCDEF"[(tud_network_mac_address[i] >> 0) & 0xf];
-    }
-  }
-  else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    case STRID_MAC:
+      // Convert MAC address into UTF-16
+      for (unsigned i=0; i<sizeof(tud_network_mac_address); i++) {
+        _desc_str[1+chr_count++] = "0123456789ABCDEF"[(tud_network_mac_address[i] >> 4) & 0xf];
+        _desc_str[1+chr_count++] = "0123456789ABCDEF"[(tud_network_mac_address[i] >> 0) & 0xf];
+      }
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > (TU_ARRAY_SIZE(_desc_str) - 1)) chr_count = TU_ARRAY_SIZE(_desc_str) - 1;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for (unsigned int i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
diff --git a/examples/device/uac2_headset/src/usb_descriptors.c b/examples/device/uac2_headset/src/usb_descriptors.c
index 682774b72..6d1e6a23f 100644
--- a/examples/device/uac2_headset/src/usb_descriptors.c
+++ b/examples/device/uac2_headset/src/usb_descriptors.c
@@ -24,6 +24,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -126,52 +127,65 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 },  // 0: is supported language is English (0x0409)
   "TinyUSB",                      // 1: Manufacturer
   "TinyUSB headset",              // 2: Product
-  "000001",                       // 3: Serials, should use chip ID
+  NULL,                           // 3: Serials will use unique ID if possible
   "TinyUSB Speakers",             // 4: Audio Interface
   "TinyUSB Microphone",           // 5: Audio Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
-  (void)langid;
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
+  (void) langid;
+  size_t chr_count;
 
-  uint8_t chr_count;
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  if (index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }
-  else
-  {
-    // Convert ASCII string into UTF-16
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if (!(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0]))) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if (chr_count > 31) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    for (uint8_t i = 0; i < chr_count; i++)
-    {
-      _desc_str[1 + i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/usbtmc/src/usb_descriptors.c b/examples/device/usbtmc/src/usb_descriptors.c
index ff682ff97..54948291e 100644
--- a/examples/device/usbtmc/src/usb_descriptors.c
+++ b/examples/device/usbtmc/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "class/usbtmc/usbtmc.h"
 #include "class/usbtmc/usbtmc_device.h"
@@ -188,55 +189,64 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB USBTMC",              // 4: USBTMC
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
-
   size_t chr_count;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }
-  else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
+
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
+
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) {
-      chr_count = 31;
-    }
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t)((((uint16_t)TUSB_DESC_STRING) << 8 ) | (2u*chr_count + 2u));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/video_capture/src/usb_descriptors.c b/examples/device/video_capture/src/usb_descriptors.c
index 9847cf7c5..292d86cd9 100644
--- a/examples/device/video_capture/src/usb_descriptors.c
+++ b/examples/device/video_capture/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -150,52 +151,64 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB UVC",                 // 4: UVC Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/device/webusb_serial/src/usb_descriptors.c b/examples/device/webusb_serial/src/usb_descriptors.c
index b2593001c..b01fae8e3 100644
--- a/examples/device/webusb_serial/src/usb_descriptors.c
+++ b/examples/device/webusb_serial/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 #include "usb_descriptors.h"
 
@@ -207,53 +208,65 @@ TU_VERIFY_STATIC(sizeof(desc_ms_os_20) == MS_OS_20_DESC_LEN, "Incorrect size");
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456",                      // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB CDC",                 // 4: CDC Interface
   "TinyUSB WebUSB"               // 5: Vendor Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }
diff --git a/examples/dual/host_hid_to_device_cdc/src/usb_descriptors.c b/examples/dual/host_hid_to_device_cdc/src/usb_descriptors.c
index 63b6bc603..293620042 100644
--- a/examples/dual/host_hid_to_device_cdc/src/usb_descriptors.c
+++ b/examples/dual/host_hid_to_device_cdc/src/usb_descriptors.c
@@ -23,6 +23,7 @@
  *
  */
 
+#include "bsp/board_api.h"
 #include "tusb.h"
 
 /* A combination of interfaces must have a unique product id, since PC will save device driver after the first plug.
@@ -214,52 +215,64 @@ uint8_t const * tud_descriptor_configuration_cb(uint8_t index)
 // String Descriptors
 //--------------------------------------------------------------------+
 
+// String Descriptor Index
+enum {
+  STRID_LANGID = 0,
+  STRID_MANUFACTURER,
+  STRID_PRODUCT,
+  STRID_SERIAL,
+};
+
 // array of pointer to string descriptors
-char const* string_desc_arr [] =
+char const *string_desc_arr[] =
 {
   (const char[]) { 0x09, 0x04 }, // 0: is supported language is English (0x0409)
   "TinyUSB",                     // 1: Manufacturer
   "TinyUSB Device",              // 2: Product
-  "123456789012",                // 3: Serials, should use chip ID
+  NULL,                          // 3: Serials will use unique ID if possible
   "TinyUSB CDC",                 // 4: CDC Interface
 };
 
-static uint16_t _desc_str[32];
+static uint16_t _desc_str[32 + 1];
 
 // Invoked when received GET STRING DESCRIPTOR request
 // Application return pointer to descriptor, whose contents must exist long enough for transfer to complete
-uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
-{
+uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
   (void) langid;
+  size_t chr_count;
+
+  switch ( index ) {
+    case STRID_LANGID:
+      memcpy(&_desc_str[1], string_desc_arr[0], 2);
+      chr_count = 1;
+      break;
 
-  uint8_t chr_count;
+    case STRID_SERIAL:
+      chr_count = board_usb_get_serial(_desc_str + 1, 32);
+      break;
 
-  if ( index == 0)
-  {
-    memcpy(&_desc_str[1], string_desc_arr[0], 2);
-    chr_count = 1;
-  }else
-  {
-    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
-    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
+    default:
+      // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+      // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
-    if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
+      if ( !(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0])) ) return NULL;
 
-    const char* str = string_desc_arr[index];
+      const char *str = string_desc_arr[index];
 
-    // Cap at max char
-    chr_count = (uint8_t) strlen(str);
-    if ( chr_count > 31 ) chr_count = 31;
+      // Cap at max char
+      chr_count = strlen(str);
+      size_t const max_count = sizeof(_desc_str) / sizeof(_desc_str[0]) - 1; // -1 for string type
+      if ( chr_count > max_count ) chr_count = max_count;
 
-    // Convert ASCII string into UTF-16
-    for(uint8_t i=0; i<chr_count; i++)
-    {
-      _desc_str[1+i] = str[i];
-    }
+      // Convert ASCII string into UTF-16
+      for ( size_t i = 0; i < chr_count; i++ ) {
+        _desc_str[1 + i] = str[i];
+      }
+      break;
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8 ) | (2*chr_count + 2));
+  _desc_str[0] = (uint16_t) ((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
 
   return _desc_str;
 }