Merge pull request #414 from mjrgh/patch-1

Fix KL25Z connect problem with some USB 3.0 hosts

libraries/USBDevice/USBDevice/USBDevice.cpp

@@ -187,7 +187,27 @@ bool USBDevice::controlOut(void)
     /* Check we should be transferring data OUT */
     if (transfer.direction != HOST_TO_DEVICE)
     {
-        return false;
+#if defined(TARGET_KL25Z) | defined(TARGET_KL46Z) | defined(TARGET_K20D5M) | defined(TARGET_K64F)
+        /*
+         * We seem to have a pending device-to-host transfer.  The host must have
+         * sent a new control request without waiting for us to finish processing
+         * the previous one.  This appears to happen when we're connected to certain 
+         * USB 3.0 host chip set. Do a zeor-length send to tell the host we're not
+         * ready for the new request - that'll make it resend - and then just
+         * pretend we were successful here so that the pending transfer can finish.
+         */
+         uint8_t buf[1] = { 0 };
+         EP0write(buf, 0);
+         
+         /* execute our pending ttransfer */
+         controlIn();
+         
+         /* indicate success */
+         return true;
+ #else
+         /* for other platforms, count on the HAL to handle this case */
+         return false;
+ #endif
     }
 
     /* Read from endpoint */