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

diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c
index 458a505..90c23b7 100644 (file)
--- a/Projects/XPLAINBridge/Lib/SoftUART.c
+++ b/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)
 {
 /** 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 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;

 
 

-       /* 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. */
 }
 
 /** 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--;
        }
                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);
        {
                /* Start bit - TX line low */
                STXPORT &= ~(1 << STX);

diff --git a/Projects/XPLAINBridge/XPLAINBridge.c b/Projects/XPLAINBridge/XPLAINBridge.c
index c08dfe9..1f00703 100644 (file)
--- a/Projects/XPLAINBridge/XPLAINBridge.c
+++ b/Projects/XPLAINBridge/XPLAINBridge.c
@@ -180,7 +180,7 @@ void EVENT_USB_Device_ConfigurationChanged(void)
        {
                EndpointConfigSuccess &= CDC_Device_ConfigureEndpoints(&VirtualSerial_CDC_Interface);
 
        {
                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
                TCCR0B = ((1 << CS02) | (1 << CS00));
        }
        else