A fix for the SerialUSB buffer overflow bug.

Send the data in chunks based on the buffer size
instead of assuming that the whole send data
will fit into the buffer.

Author: GabrielNotman

cores/arduino/USB/USBCore.cpp

@@ -120,12 +120,32 @@ uint32_t USBD_Send(uint32_t ep, const void* d, uint32_t len)
 	int r = len;
 	const uint8_t* data = (const uint8_t*)d;
 
-    if (!_usbConfiguration)
-    {
-    	TRACE_CORE(printf("pb conf\n\r");)
+  if (!_usbConfiguration)
+  {
+  	TRACE_CORE(printf("pb conf\n\r");)
 		return -1;
-    }
-	UDD_Send(ep, data, len);
+  }
+
+  size_t i = 0;
+  // Ensure the chunk size is aligned 4
+  size_t chunkSize = UDD_IN_CACHE_SIZE -(UDD_IN_CACHE_SIZE % 4);
+
+  // Send the full chunks
+  for (i = 0; i < (len / chunkSize); i++)
+  {
+    UDD_Send(ep, data + (i*chunkSize), chunkSize);
+
+    /* Clear the transfer complete flag  */
+    udd_clear_IN_transf_cplt(ep);
+    /* Set the bank as ready */
+    udd_IN_transfer_allowed(ep);
+
+    /* Wait for transfer to complete */
+    while (!udd_is_IN_transf_cplt(ep));  // need fire exit.
+  }
+
+  // Send the remainder
+  UDD_Send(ep, data + (i * chunkSize), len % chunkSize);
 
 	/* Clear the transfer complete flag  */
 	udd_clear_IN_transf_cplt(ep);

cores/arduino/USB/samd21_device.c

@@ -34,8 +34,8 @@ extern "C"{
 //#define TRACE_DEVICE(x)	x
 #define TRACE_DEVICE(x)
 
-__attribute__((__aligned__(4))) /*__attribute__((__section__(".bss_hram0")))*/ uint8_t udd_ep_out_cache_buffer[4][64];
-__attribute__((__aligned__(4))) /*__attribute__((__section__(".bss_hram0")))*/ uint8_t udd_ep_in_cache_buffer[4][128];
+__attribute__((__aligned__(4))) /*__attribute__((__section__(".bss_hram0")))*/ uint8_t udd_ep_out_cache_buffer[4][UDD_OUT_CACHE_SIZE];
+__attribute__((__aligned__(4))) /*__attribute__((__section__(".bss_hram0")))*/ uint8_t udd_ep_in_cache_buffer[4][UDD_IN_CACHE_SIZE];
 
 /**
  * USB SRAM data containing pipe descriptor table

cores/arduino/USB/samd21_device.h

@@ -26,6 +26,9 @@ extern "C" {
 #define EP0				0
 #define EPX_SIZE		64// 64 for Full Speed, EPT size max is 1024
 
+#define UDD_OUT_CACHE_SIZE 64
+#define UDD_IN_CACHE_SIZE 128
+
 // Force device low speed mode
 #define udd_force_low_speed()               USB->DEVICE.CTRLB.reg &= ~USB_DEVICE_CTRLB_SPDCONF_Msk; USB->DEVICE.CTRLB.reg |= USB_DEVICE_CTRLB_SPDCONF_1_Val
 // Force full speed mode