3 files changed, 28 insertions, 10 deletions
diff --git a/src/common/tusb_types.h b/src/common/tusb_types.h
index e11f08dd1..1bfa7c7d1 100644
--- a/src/common/tusb_types.h
+++ b/src/common/tusb_types.h
@@ -225,7 +225,7 @@ enum {
 
 typedef enum
 {
-  XFER_RESULT_SUCCESS,
+  XFER_RESULT_SUCCESS = 0,
   XFER_RESULT_FAILED,
   XFER_RESULT_STALLED,
   XFER_RESULT_TIMEOUT,
diff --git a/src/host/usbh.c b/src/host/usbh.c
index 9d618db92..a5abac843 100644
--- a/src/host/usbh.c
+++ b/src/host/usbh.c
@@ -620,9 +620,7 @@ static void _xfer_complete(uint8_t daddr, xfer_result_t result)
     .user_data   = _ctrl_xfer.user_data
   };
 
-  usbh_lock();
-  _ctrl_xfer.stage = CONTROL_STAGE_IDLE;
-  usbh_unlock();
+  _set_control_xfer_stage(CONTROL_STAGE_IDLE);
 
   if (xfer_temp.complete_cb)
   {
@@ -1182,12 +1180,28 @@ static void enum_full_complete(void);
 // process device enumeration
 static void process_enumeration(tuh_xfer_t* xfer)
 {
+  // Retry a few times with transfers in enumeration since device can be unstable when starting up
+  enum {
+    ATTEMPT_COUNT_MAX = 3,
+    ATTEMPT_DELAY_MS = 10
+  };
+  static uint8_t failed_count = 0;
+
   if (XFER_RESULT_SUCCESS != xfer->result)
   {
-    // stop enumeration, maybe we could retry this
-    enum_full_complete();
+    // retry if not reaching max attempt
+    if ( failed_count < ATTEMPT_COUNT_MAX )
+    {
+      failed_count++;
+      osal_task_delay(ATTEMPT_DELAY_MS); // delay a bit
+      TU_ASSERT(tuh_control_xfer(xfer), );
+    }else
+    {
+      enum_full_complete();
+    }
     return;
   }
+  failed_count = 0;
 
   uint8_t const daddr = xfer->daddr;
   uintptr_t const state = xfer->user_data;
diff --git a/src/host/usbh.h b/src/host/usbh.h
index 1a26a69b4..37de7093c 100644
--- a/src/host/usbh.h
+++ b/src/host/usbh.h
@@ -51,14 +51,15 @@ struct tuh_xfer_s
 {
   uint8_t daddr;
   uint8_t ep_addr;
-
+  uint8_t TU_RESERVED;      // reserved
   xfer_result_t result;
+
   uint32_t actual_len;      // excluding setup packet
 
   union
   {
     tusb_control_request_t const* setup; // setup packet pointer if control transfer
-    uint32_t buflen;        // expected length if not control transfer (not available in callback)
+    uint32_t buflen;                     // expected length if not control transfer (not available in callback)
   };
 
   uint8_t* buffer;           // not available in callback if not control transfer
@@ -80,10 +81,13 @@ enum
 
 //TU_ATTR_WEAK uint8_t tuh_attach_cb (tusb_desc_device_t const *desc_device);
 
-// Invoked when device is mounted (configured)
+// Invoked when a device is mounted (configured)
 TU_ATTR_WEAK void tuh_mount_cb (uint8_t daddr);
 
-/// Invoked when device is unmounted (bus reset/unplugged)
+// Invoked when a device failed to mount during enumeration process
+// TU_ATTR_WEAK void tuh_mount_failed_cb (uint8_t daddr);
+
+/// Invoked when a device is unmounted (detached)
 TU_ATTR_WEAK void tuh_umount_cb(uint8_t daddr);
 
 //--------------------------------------------------------------------+