1 files changed, 68 insertions, 24 deletions

diff --git a/cores/arduino/CDC.cpp b/cores/arduino/CDC.cpp
index 14a0eae..94faf2e 100644
--- a/cores/arduino/CDC.cpp
+++ b/cores/arduino/CDC.cpp
@@ -23,12 +23,20 @@
 #if defined(USBCON)
 #ifdef CDC_ENABLED
 
-void Reboot()
+#if (RAMEND < 1000)
+#define SERIAL_BUFFER_SIZE 16
+#else
+#define SERIAL_BUFFER_SIZE 64
+#endif
+
+struct ring_buffer
 {
-	USB.detach();
-	cli();
-	asm volatile("jmp 0x7800");		// jump to bootloader - DiskLoader takes up last 2 kB
-}
+	unsigned char buffer[SERIAL_BUFFER_SIZE];
+	volatile int head;
+	volatile int tail;
+};
+
+ring_buffer cdc_rx_buffer = { { 0 }, 0, 0};
 
 typedef struct
 {
@@ -92,9 +100,29 @@ bool WEAK CDC_Setup(Setup& setup)
 
 		if (CDC_SET_CONTROL_LINE_STATE == r)
 		{
-			if (0 != _usbLineInfo.lineState && 1200 == _usbLineInfo.dwDTERate)	// auto-reset is triggered when the port, already open at 1200 bps, is closed
-				Reboot();
 			_usbLineInfo.lineState = setup.wValueL;
+
+			// auto-reset into the bootloader is triggered when the port, already 
+			// open at 1200 bps, is closed.  this is the signal to start the watchdog
+			// with a relatively long period so it can finish housekeeping tasks
+			// like servicing endpoints before the sketch ends
+			if (1200 == _usbLineInfo.dwDTERate) {
+				// We check DTR state to determine if host port is open (bit 0 of lineState).
+				// Serial1.print(">"); Serial1.println(_usbLineInfo.lineState, HEX);
+				if ((_usbLineInfo.lineState & 0x01) == 0) {
+					*(uint16_t *)0x0A00 = 0x7777;
+					wdt_enable(WDTO_250MS);
+				} else {
+					// Most OSs do some intermediate steps when configuring ports and DTR can
+					// twiggle more than once before stabilizing.
+					// To avoid spurious resets we set the watchdog to 250ms and eventually
+					// cancel if DTR goes back high.
+	
+					wdt_disable();
+					wdt_reset();
+					*(uint16_t *)0x0A00 = 0x0;
+				}
+			}
 			return true;
 		}
 	}
@@ -111,33 +139,49 @@ void Serial_::end(void)
 {
 }
 
+void Serial_::accept(void) 
+{
+	ring_buffer *buffer = &cdc_rx_buffer;
+	int c = USB_Recv(CDC_RX); 
+	int i = (unsigned int)(buffer->head+1) % SERIAL_BUFFER_SIZE;
+	
+	// if we should be storing the received character into the location
+	// just before the tail (meaning that the head would advance to the
+	// current location of the tail), we're about to overflow the buffer
+	// and so we don't write the character or advance the head.
+	if (i != buffer->tail) {
+		buffer->buffer[buffer->head] = c;
+		buffer->head = i;
+	}
+}
+
 int Serial_::available(void)
 {
-	u8 avail = USB_Available(CDC_RX);
-	if (_serialPeek != -1)
-		avail++;
-	return avail;
+	ring_buffer *buffer = &cdc_rx_buffer;
+	return (unsigned int)(SERIAL_BUFFER_SIZE + buffer->head - buffer->tail) % SERIAL_BUFFER_SIZE;
 }
 
-//	peek is nasty
 int Serial_::peek(void)
 {
-	if (_serialPeek == -1)
-		_serialPeek = read();
-	return _serialPeek;
+	ring_buffer *buffer = &cdc_rx_buffer;
+	if (buffer->head == buffer->tail) {
+		return -1;
+	} else {
+		return buffer->buffer[buffer->tail];
+	}
 }
 
 int Serial_::read(void)
 {
-	int c;
-	if (_serialPeek != -1)
-	{
-		c = _serialPeek;
-		_serialPeek = -1;
+	ring_buffer *buffer = &cdc_rx_buffer;
+	// if the head isn't ahead of the tail, we don't have any characters
+	if (buffer->head == buffer->tail) {
+		return -1;
 	} else {
-		c = USB_Recv(CDC_RX);
-	}
-	return c;
+		unsigned char c = buffer->buffer[buffer->tail];
+		buffer->tail = (unsigned int)(buffer->tail + 1) % SERIAL_BUFFER_SIZE;
+		return c;
+	}	
 }
 
 void Serial_::flush(void)
@@ -172,4 +216,4 @@ size_t Serial_::write(uint8_t c)
 Serial_ Serial;
 
 #endif
-#endif /* if defined(USBCON) */
\ No newline at end of file
+#endif /* if defined(USBCON) */