Add glitch protection to the software UART in the XPLAINBridge project code,...

Add glitch protection to the software UART in the XPLAINBridge project code, so that very short glitches on the RX line don't cause a frame reception to occur.

Projects/XPLAINBridge/Lib/SoftUART.c

@@ -76,15 +76,21 @@ void SoftUART_Init(void)
 /** ISR to detect the start of a bit being sent to the software UART. */
 ISR(INT0_vect, ISR_BLOCK)
 {
-	/* Reset and start the reception timer */
-	TCNT1  = 0;
-	TCCR1B = ((1 << CS10) | (1 << WGM12));
-
 	/* Reset the number of reception bits remaining counter */
 	RX_BitsRemaining = 8;
 	
+	/* Reset the bit reception timer */
+	TCNT1 = 0;
+
+	/* Check to see that the pin is still low (prevents glitches from starting a frame reception) */
+	if (!(SRXPIN & (1 << SRX)))
+	{
 		/* Disable start bit detection ISR while the next byte is received */
 		EIMSK = 0;
+
+		/* Start the reception timer */
+		TCCR1B = ((1 << CS10) | (1 << WGM12));
+	}
 }
 
 /** ISR to manage the reception of bits to the software UART. */
@@ -133,7 +139,7 @@ ISR(TIMER3_COMPA_vect, ISR_NOBLOCK)
 		TX_Data >>= 1;
 		TX_BitsRemaining--;
 	}
-	else if (USBtoUART_Buffer.Count)
+	else if (USBtoUART_Buffer.Count && !(RX_BitsRemaining))
 	{
 		/* Start bit - TX line low */
 		STXPORT &= ~(1 << STX);

Projects/XPLAINBridge/XPLAINBridge.c

@@ -180,7 +180,7 @@ void EVENT_USB_Device_ConfigurationChanged(void)
 	{
 		EndpointConfigSuccess &= CDC_Device_ConfigureEndpoints(&VirtualSerial_CDC_Interface);
 
-		/* Configure the UART flush timer */
+		/* Configure the UART flush timer - run at FCPU/1024 for maximum interval before overflow */
 		TCCR0B = ((1 << CS02) | (1 << CS00));
 	}
 	else