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authorhathach <[email protected]>2024-11-21 17:49:38 +0700
committerhathach <[email protected]>2024-11-21 17:49:38 +0700
commitdbdc5a239c42e96eeeb8759a121798fa9b3f39c3 (patch)
tree0e5dadec079b5509ba5f9a5770092001b87f76b6 /examples/device/midi_test_freertos/src
parent5d77faa835ab7faf73a9981905e57e8d79920d2d (diff)
- move freertos_hooks to board.c
- add device/midi_test_freertos example - update bth/dfu/midi device for cache line size
Diffstat (limited to 'examples/device/midi_test_freertos/src')
-rw-r--r--examples/device/midi_test_freertos/src/CMakeLists.txt4
-rw-r--r--examples/device/midi_test_freertos/src/main.c239
-rw-r--r--examples/device/midi_test_freertos/src/tusb_config.h108
-rw-r--r--examples/device/midi_test_freertos/src/usb_descriptors.c199
4 files changed, 550 insertions, 0 deletions
diff --git a/examples/device/midi_test_freertos/src/CMakeLists.txt b/examples/device/midi_test_freertos/src/CMakeLists.txt
new file mode 100644
index 000000000..9bd427c89
--- /dev/null
+++ b/examples/device/midi_test_freertos/src/CMakeLists.txt
@@ -0,0 +1,4 @@
+# This file is for ESP-IDF only
+idf_component_register(SRCS main.c usb_descriptors.c
+ INCLUDE_DIRS "."
+ REQUIRES boards tinyusb_src)
diff --git a/examples/device/midi_test_freertos/src/main.c b/examples/device/midi_test_freertos/src/main.c
new file mode 100644
index 000000000..dbe89080c
--- /dev/null
+++ b/examples/device/midi_test_freertos/src/main.c
@@ -0,0 +1,239 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Ha Thach (tinyusb.org)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "bsp/board_api.h"
+#include "tusb.h"
+
+/* This MIDI example send sequence of note (on/off) repeatedly. To test on PC, you need to install
+ * synth software and midi connection management software. On
+ * - Linux (Ubuntu): install qsynth, qjackctl. Then connect TinyUSB output port to FLUID Synth input port
+ * - Windows: install MIDI-OX
+ * - MacOS: SimpleSynth
+ */
+
+//--------------------------------------------------------------------+
+// MACRO CONSTANT TYPEDEF PROTYPES
+//--------------------------------------------------------------------+
+#if TUSB_MCU_VENDOR_ESPRESSIF
+ #define USBD_STACK_SIZE 4096
+#else
+ // Increase stack size when debug log is enabled
+ #define USBD_STACK_SIZE (3*configMINIMAL_STACK_SIZE/2) * (CFG_TUSB_DEBUG ? 2 : 1)
+#endif
+
+#define BLINKY_STACK_SIZE configMINIMAL_STACK_SIZE
+#define MIDI_STACK_SIZE configMINIMAL_STACK_SIZE
+
+// static task
+#if configSUPPORT_STATIC_ALLOCATION
+StackType_t blinky_stack[BLINKY_STACK_SIZE];
+StaticTask_t blinky_taskdef;
+
+StackType_t usb_device_stack[USBD_STACK_SIZE];
+StaticTask_t usb_device_taskdef;
+
+StackType_t midi_stack[MIDI_STACK_SIZE];
+StaticTask_t midi_taskdef;
+#endif
+
+/* Blink pattern
+ * - 250 ms : device not mounted
+ * - 1000 ms : device mounted
+ * - 2500 ms : device is suspended
+ */
+enum {
+ BLINK_NOT_MOUNTED = 250,
+ BLINK_MOUNTED = 1000,
+ BLINK_SUSPENDED = 2500,
+};
+
+static uint32_t blink_interval_ms = BLINK_NOT_MOUNTED;
+
+void usb_device_task(void *param);
+void led_blinking_task(void* param);
+void midi_task(void* param);
+
+//--------------------------------------------------------------------+
+// Main
+//--------------------------------------------------------------------+
+int main(void) {
+ board_init();
+
+#if configSUPPORT_STATIC_ALLOCATION
+ xTaskCreateStatic(led_blinking_task, "blinky", BLINKY_STACK_SIZE, NULL, 1, blinky_stack, &blinky_taskdef);
+ xTaskCreateStatic(usb_device_task, "usbd", USBD_STACK_SIZE, NULL, configMAX_PRIORITIES-1, usb_device_stack, &usb_device_taskdef);
+ xTaskCreateStatic(midi_task, "midi", MIDI_STACK_SIZE, NULL, configMAX_PRIORITIES - 2, midi_stack, &midi_taskdef);
+#else
+ xTaskCreate(led_blinking_task, "blinky", BLINKY_STACK_SIZE, NULL, 1, NULL);
+ xTaskCreate(usb_device_task, "usbd", USBD_STACK_SIZE, NULL, configMAX_PRIORITIES - 1, NULL);
+ xTaskCreate(midi_task, "midi", MIDI_STACK_SIZE, NULL, configMAX_PRIORITIES - 2, NULL);
+#endif
+
+#if !TUSB_MCU_VENDOR_ESPRESSIF
+ // skip starting scheduler (and return) for ESP32-S2 or ESP32-S3
+ vTaskStartScheduler();
+#endif
+
+ return 0;
+}
+
+#if TUSB_MCU_VENDOR_ESPRESSIF
+void app_main(void) {
+ main();
+}
+#endif
+
+// USB Device Driver task
+// This top level thread process all usb events and invoke callbacks
+void usb_device_task(void *param) {
+ (void) param;
+
+ // init device stack on configured roothub port
+ // This should be called after scheduler/kernel is started.
+ // Otherwise it could cause kernel issue since USB IRQ handler does use RTOS queue API.
+ tusb_rhport_init_t dev_init = {
+ .role = TUSB_ROLE_DEVICE,
+ .speed = TUSB_SPEED_AUTO
+ };
+ tusb_init(BOARD_TUD_RHPORT, &dev_init);
+
+ if (board_init_after_tusb) {
+ board_init_after_tusb();
+ }
+
+ // RTOS forever loop
+ while (1) {
+ // put this thread to waiting state until there is new events
+ tud_task();
+ }
+}
+
+//--------------------------------------------------------------------+
+// Device callbacks
+//--------------------------------------------------------------------+
+
+// Invoked when device is mounted
+void tud_mount_cb(void) {
+ blink_interval_ms = BLINK_MOUNTED;
+}
+
+// Invoked when device is unmounted
+void tud_umount_cb(void) {
+ blink_interval_ms = BLINK_NOT_MOUNTED;
+}
+
+// Invoked when usb bus is suspended
+// remote_wakeup_en : if host allow us to perform remote wakeup
+// Within 7ms, device must draw an average of current less than 2.5 mA from bus
+void tud_suspend_cb(bool remote_wakeup_en) {
+ (void) remote_wakeup_en;
+ blink_interval_ms = BLINK_SUSPENDED;
+}
+
+// Invoked when usb bus is resumed
+void tud_resume_cb(void) {
+ blink_interval_ms = tud_mounted() ? BLINK_MOUNTED : BLINK_NOT_MOUNTED;
+}
+
+//--------------------------------------------------------------------+
+// MIDI Task
+//--------------------------------------------------------------------+
+
+// Store example melody as an array of note values
+const uint8_t note_sequence[] = {
+ 74,78,81,86,90,93,98,102,57,61,66,69,73,78,81,85,88,92,97,100,97,92,88,85,81,78,
+ 74,69,66,62,57,62,66,69,74,78,81,86,90,93,97,102,97,93,90,85,81,78,73,68,64,61,
+ 56,61,64,68,74,78,81,86,90,93,98,102
+};
+
+void midi_task(void* param) {
+ (void) param;
+
+ const uint8_t cable_num = 0; // MIDI jack associated with USB endpoint
+ const uint8_t channel = 0; // 0 for channel 1
+
+ // Variable that holds the current position in the sequence.
+ uint32_t note_pos = 0;
+
+ while (1) {
+ // send note periodically
+ vTaskDelay(286 / portTICK_PERIOD_MS);
+
+ // Previous positions in the note sequence.
+ int previous = (int) (note_pos - 1);
+
+ // If we currently are at position 0, set the
+ // previous position to the last note in the sequence.
+ if (previous < 0) {
+ previous = sizeof(note_sequence) - 1;
+ }
+
+ // Send Note On for current position at full velocity (127) on channel 1.
+ uint8_t note_on[3] = { 0x90 | channel, note_sequence[note_pos], 127 };
+ tud_midi_stream_write(cable_num, note_on, 3);
+
+ // Send Note Off for previous note.
+ uint8_t note_off[3] = { 0x80 | channel, note_sequence[previous], 0};
+ tud_midi_stream_write(cable_num, note_off, 3);
+
+ // Increment position
+ note_pos++;
+
+ // If we are at the end of the sequence, start over.
+ if (note_pos >= sizeof(note_sequence)) {
+ note_pos = 0;
+ }
+
+ // The MIDI interface always creates input and output port/jack descriptors
+ // regardless of these being used or not. Therefore incoming traffic should be read
+ // (possibly just discarded) to avoid the sender blocking in IO
+ while (tud_midi_available()) {
+ uint8_t packet[4];
+ tud_midi_packet_read(packet);
+ }
+ }
+}
+
+//--------------------------------------------------------------------+
+// BLINKING TASK
+//--------------------------------------------------------------------+
+void led_blinking_task(void* param) {
+ (void) param;
+ static uint32_t start_ms = 0;
+ static bool led_state = false;
+
+ while (1) {
+ // Blink every interval ms
+ vTaskDelay(blink_interval_ms / portTICK_PERIOD_MS);
+ start_ms += blink_interval_ms;
+
+ board_led_write(led_state);
+ led_state = 1 - led_state; // toggle
+ }
+}
diff --git a/examples/device/midi_test_freertos/src/tusb_config.h b/examples/device/midi_test_freertos/src/tusb_config.h
new file mode 100644
index 000000000..314dde438
--- /dev/null
+++ b/examples/device/midi_test_freertos/src/tusb_config.h
@@ -0,0 +1,108 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Ha Thach (tinyusb.org)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ */
+
+#ifndef _TUSB_CONFIG_H_
+#define _TUSB_CONFIG_H_
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+//--------------------------------------------------------------------+
+// Board Specific Configuration
+//--------------------------------------------------------------------+
+
+// RHPort number used for device can be defined by board.mk, default to port 0
+#ifndef BOARD_TUD_RHPORT
+#define BOARD_TUD_RHPORT 0
+#endif
+
+// RHPort max operational speed can defined by board.mk
+#ifndef BOARD_TUD_MAX_SPEED
+#define BOARD_TUD_MAX_SPEED OPT_MODE_DEFAULT_SPEED
+#endif
+
+//--------------------------------------------------------------------
+// COMMON CONFIGURATION
+//--------------------------------------------------------------------
+
+// defined by compiler flags for flexibility
+#ifndef CFG_TUSB_MCU
+#error CFG_TUSB_MCU must be defined
+#endif
+
+#ifndef CFG_TUSB_OS
+#define CFG_TUSB_OS OPT_OS_NONE
+#endif
+
+#ifndef CFG_TUSB_DEBUG
+#define CFG_TUSB_DEBUG 0
+#endif
+
+// Enable Device stack
+#define CFG_TUD_ENABLED 1
+
+// Default is max speed that hardware controller could support with on-chip PHY
+#define CFG_TUD_MAX_SPEED BOARD_TUD_MAX_SPEED
+
+/* USB DMA on some MCUs can only access a specific SRAM region with restriction on alignment.
+ * Tinyusb use follows macros to declare transferring memory so that they can be put
+ * into those specific section.
+ * e.g
+ * - CFG_TUSB_MEM SECTION : __attribute__ (( section(".usb_ram") ))
+ * - CFG_TUSB_MEM_ALIGN : __attribute__ ((aligned(4)))
+ */
+#ifndef CFG_TUSB_MEM_SECTION
+#define CFG_TUSB_MEM_SECTION
+#endif
+
+#ifndef CFG_TUSB_MEM_ALIGN
+#define CFG_TUSB_MEM_ALIGN __attribute__ ((aligned(4)))
+#endif
+
+//--------------------------------------------------------------------
+// DEVICE CONFIGURATION
+//--------------------------------------------------------------------
+
+#ifndef CFG_TUD_ENDPOINT0_SIZE
+#define CFG_TUD_ENDPOINT0_SIZE 64
+#endif
+
+//------------- CLASS -------------//
+#define CFG_TUD_CDC 0
+#define CFG_TUD_MSC 0
+#define CFG_TUD_HID 0
+#define CFG_TUD_MIDI 1
+#define CFG_TUD_VENDOR 0
+
+// MIDI FIFO size of TX and RX
+#define CFG_TUD_MIDI_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
+#define CFG_TUD_MIDI_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif /* _TUSB_CONFIG_H_ */
diff --git a/examples/device/midi_test_freertos/src/usb_descriptors.c b/examples/device/midi_test_freertos/src/usb_descriptors.c
new file mode 100644
index 000000000..384742ae8
--- /dev/null
+++ b/examples/device/midi_test_freertos/src/usb_descriptors.c
@@ -0,0 +1,199 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Ha Thach (tinyusb.org)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ */
+
+#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] 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) | \
+ _PID_MAP(MIDI, 3) | _PID_MAP(VENDOR, 4) )
+
+//--------------------------------------------------------------------+
+// Device Descriptors
+//--------------------------------------------------------------------+
+tusb_desc_device_t const desc_device = {
+ .bLength = sizeof(tusb_desc_device_t),
+ .bDescriptorType = TUSB_DESC_DEVICE,
+ .bcdUSB = 0x0200,
+ .bDeviceClass = 0x00,
+ .bDeviceSubClass = 0x00,
+ .bDeviceProtocol = 0x00,
+ .bMaxPacketSize0 = CFG_TUD_ENDPOINT0_SIZE,
+
+ .idVendor = 0xCafe,
+ .idProduct = USB_PID,
+ .bcdDevice = 0x0100,
+
+ .iManufacturer = 0x01,
+ .iProduct = 0x02,
+ .iSerialNumber = 0x03,
+
+ .bNumConfigurations = 0x01
+};
+
+// Invoked when received GET DEVICE DESCRIPTOR
+// Application return pointer to descriptor
+uint8_t const * tud_descriptor_device_cb(void) {
+ return (uint8_t const *) &desc_device;
+}
+//--------------------------------------------------------------------+
+// Configuration Descriptor
+//--------------------------------------------------------------------+
+enum {
+ ITF_NUM_MIDI = 0,
+ ITF_NUM_MIDI_STREAMING,
+ ITF_NUM_TOTAL
+};
+
+#define CONFIG_TOTAL_LEN (TUD_CONFIG_DESC_LEN + TUD_MIDI_DESC_LEN)
+
+#if CFG_TUSB_MCU == OPT_MCU_LPC175X_6X || CFG_TUSB_MCU == OPT_MCU_LPC177X_8X || CFG_TUSB_MCU == OPT_MCU_LPC40XX
+ // LPC 17xx and 40xx endpoint type (bulk/interrupt/iso) are fixed by its number
+ // 0 control, 1 In, 2 Bulk, 3 Iso, 4 In etc ...
+ #define EPNUM_MIDI_OUT 0x02
+ #define EPNUM_MIDI_IN 0x82
+
+#elif CFG_TUSB_MCU == OPT_MCU_CXD56
+ // CXD56 USB driver has fixed endpoint type (bulk/interrupt/iso) and direction (IN/OUT) by its number
+ // 0 control (IN/OUT), 1 Bulk (IN), 2 Bulk (OUT), 3 In (IN), 4 Bulk (IN), 5 Bulk (OUT), 6 In (IN)
+ #define EPNUM_MIDI_OUT 0x02
+ #define EPNUM_MIDI_IN 0x81
+
+#elif defined(TUD_ENDPOINT_ONE_DIRECTION_ONLY)
+ // MCUs that don't support a same endpoint number with different direction IN and OUT defined in tusb_mcu.h
+ // e.g EP1 OUT & EP1 IN cannot exist together
+ #define EPNUM_MIDI_OUT 0x01
+ #define EPNUM_MIDI_IN 0x82
+
+#else
+ #define EPNUM_MIDI_OUT 0x01
+ #define EPNUM_MIDI_IN 0x81
+#endif
+
+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 Out & EP In address, EP size
+ TUD_MIDI_DESCRIPTOR(ITF_NUM_MIDI, 0, EPNUM_MIDI_OUT, (0x80 | EPNUM_MIDI_IN), 64)
+};
+
+#if TUD_OPT_HIGH_SPEED
+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 Out & EP In address, EP size
+ TUD_MIDI_DESCRIPTOR(ITF_NUM_MIDI, 0, EPNUM_MIDI_OUT, (0x80 | EPNUM_MIDI_IN), 512)
+};
+#endif
+
+// 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) {
+ (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;
+#else
+ return desc_fs_configuration;
+#endif
+}
+
+//--------------------------------------------------------------------+
+// 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)
+ "TinyUSB", // 1: Manufacturer
+ "TinyUSB Device", // 2: Product
+ NULL, // 3: Serials will use unique ID if possible
+};
+
+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;
+ size_t chr_count;
+
+ 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;
+ }
+
+ const char *str = string_desc_arr[index];
+
+ // Cap at max char
+ chr_count = strlen(str);
+ const size_t 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];
+ }
+ 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));
+
+ return _desc_str;
+}