Fix large serial command input triggering watchdog

src/bus/usart.c

@@ -48,6 +48,7 @@ void USART_Putc(char ch)
 {
 	short head;
 
+	// Wrap around if end of buffer reached
 	head = (txhead + 1) & USART_TXBUF_MASK;
 	while (head == txtail); // Wait for space
 
@@ -62,16 +63,18 @@ void USART_Putc(char ch)
 ISR(USART_RXC_vect)
 {
 	short head;
+	byte data;
 
-	// Next byte ready to read from serial
+	data = UDR; // Next byte ready
+
+	// Wrap around if end of buffer reached
 	head = (rxhead + 1) & USART_RXBUF_MASK;
+
 	// Free space in RX buffer?
+	// Otherwise discard overflow
 	if (head != rxtail) {
-		// Copy from register
+		rxbuf[head] = data;
-		rxbuf[head] = UDR;
 		rxhead = head;
-	} else {
-		// XXX: Discard overflow
 	}
 }
 

src/main.c

@@ -7,7 +7,6 @@
 #include <avr/interrupt.h>
 
 // TODO: Config header for chip specifics like EEPROM size.
-// TODO: Fix huge serial command input triggering watchdog.
 // TODO: Only update EEPROM if value differs from previous.
 // TODO: Check thermistor conversion results /w thermometer.
 // TODO: Implement primary state machine for update loop.