From ee2d18ef91153a213671c7b144d7b66ac9a6b671 Mon Sep 17 00:00:00 2001
From: Gabriel Notman <g.notman@gmail.com>
Date: Mon, 28 Sep 2015 15:57:44 +0100
Subject: [PATCH] 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.
---
 cores/arduino/USB/USBCore.cpp     | 30 +++++++++++++++++++++++++-----
 cores/arduino/USB/samd21_device.c |  4 ++--
 cores/arduino/USB/samd21_device.h |  3 +++
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/cores/arduino/USB/USBCore.cpp b/cores/arduino/USB/USBCore.cpp
index 31b8380af..a72305f7f 100644
--- a/cores/arduino/USB/USBCore.cpp
+++ b/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);
diff --git a/cores/arduino/USB/samd21_device.c b/cores/arduino/USB/samd21_device.c
index cff711f47..3aae35d9f 100644
--- a/cores/arduino/USB/samd21_device.c
+++ b/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
diff --git a/cores/arduino/USB/samd21_device.h b/cores/arduino/USB/samd21_device.h
index deded25b4..e26bb4873 100644
--- a/cores/arduino/USB/samd21_device.h
+++ b/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