If the serial buffer is full when write is called, HardwareSerial now decides whether to wait for the ISR to open up some space, or quits immediately to avoid hanging the processor. (If this situation was caused from within another ISR). Added HardwareSerial::waitForBufferSpace(uint8_t v) which takes TRUE or FALSE so the user can make that choice.

Author: hjohnson

hardware/arduino/cores/arduino/HardwareSerial.cpp

@@ -289,6 +289,7 @@ HardwareSerial::HardwareSerial(ring_buffer *rx_buffer, ring_buffer *tx_buffer,
   _rxcie = rxcie;
   _udrie = udrie;
   _u2x = u2x;
+  _serial_buffer_wait = 0x1; //by default, wait for space.
 }
 
 // Public Methods //////////////////////////////////////////////////////////////
@@ -384,11 +385,14 @@ size_t HardwareSerial::write(uint8_t c)
 {
   int i = (_tx_buffer->head + 1) % SERIAL_BUFFER_SIZE;
 
-  // If the output buffer is full, there's nothing for it other than to 
-  // wait for the interrupt handler to empty it a bit
-  // ???: return 0 here instead?
-  while (i == _tx_buffer->tail)
+  // If the output buffer is full, there's two options. Either quit or wait for interrupt handler to make space. User decides.
+ if(_serial_buffer_wait == 1) {
+	while (i == _tx_buffer->tail)
     ;
+	} else {
+	if(i == _tx_buffer->tail) { return 0; }
+	}
+
 
   _tx_buffer->buffer[_tx_buffer->head] = c;
   _tx_buffer->head = i;
@@ -398,6 +402,9 @@ size_t HardwareSerial::write(uint8_t c)
   return 1;
 }
 
+void HardwareSerial::waitForBufferSpace(uint8_t v) {
+	_serial_buffer_wait = v;
+}
 // Preinstantiate Objects //////////////////////////////////////////////////////
 
 #if defined(UBRRH) && defined(UBRRL)