USBSerial: fix sending more than CDC_MAX_PACKET_SIZE in a single shot

Fixes #85

Author: facchinm

Diff for: cores/arduino/USB/PluggableUSBSerial.h

@@ -248,7 +248,13 @@ class USBSerial: public USBCDC, public ::mbed::Stream, public HardwareSerial {
         if (!connected()) {
             return 0;
         }
-        return send((uint8_t*)buf, size);
+        size_t sent = 0;
+        while (sent < size) {
+            size_t to_send = (size - sent) > CDC_MAX_PACKET_SIZE ? CDC_MAX_PACKET_SIZE : (size - sent);
+            send((uint8_t*)&buf[sent], to_send);
+            sent += to_send;
+        }
+        return sent;
     }
     using Print::write; // pull in write(str) and write(buf, size) from Print
 

Diff for: cores/arduino/USB/USBCDC.cpp

@@ -41,12 +41,6 @@ static const uint8_t cdc_line_coding_default[7] = {0x80, 0x25, 0x00, 0x00, 0x00,
 #define CLS_DTR   (1 << 0)
 #define CLS_RTS   (1 << 1)
 
-#if defined(MBED_CONF_TARGET_USB_SPEED) && (MBED_CONF_TARGET_USB_SPEED == USE_USB_OTG_HS)
-#define CDC_MAX_PACKET_SIZE    512
-#else
-#define CDC_MAX_PACKET_SIZE    64
-#endif
-
 class USBCDC::AsyncWrite: public AsyncOp {
 public:
     AsyncWrite(USBCDC *serial, uint8_t *buf, uint32_t size):

Diff for: cores/arduino/USB/USBCDC.h

@@ -26,6 +26,12 @@
 #include "OperationList.h"
 #include "PluggableUSBDevice.h"
 
+#if defined(MBED_CONF_TARGET_USB_SPEED) && (MBED_CONF_TARGET_USB_SPEED == USE_USB_OTG_HS)
+#define CDC_MAX_PACKET_SIZE    512
+#else
+#define CDC_MAX_PACKET_SIZE    64
+#endif
+
 class AsyncOp;
 
 namespace arduino {
@@ -209,13 +215,13 @@ class USBCDC: public internal::PluggableUSBModule{
 
     OperationList<AsyncWrite> _tx_list;
     bool _tx_in_progress;
-    uint8_t _tx_buffer[512];
+    uint8_t _tx_buffer[CDC_MAX_PACKET_SIZE];
     uint8_t *_tx_buf;
     uint32_t _tx_size;
 
     OperationList<AsyncRead> _rx_list;
     bool _rx_in_progress;
-    uint8_t _rx_buffer[512];
+    uint8_t _rx_buffer[CDC_MAX_PACKET_SIZE];
     uint8_t *_rx_buf;
     uint32_t _rx_size;