More speed and quality improvements to the software USART in the AVRISP project.

1 files changed, 8 insertions, 9 deletions

diff --git a/Projects/AVRISP/Lib/PDITarget.c b/Projects/AVRISP/Lib/PDITarget.c
index e21942a1f..afcf8b81f 100644
--- a/Projects/AVRISP/Lib/PDITarget.c
+++ b/Projects/AVRISP/Lib/PDITarget.c
@@ -196,19 +196,18 @@ void PDITarget_SendByte(uint8_t Byte)
 		IsSending = true;

 	}

 

-	bool    EvenParityBit = false;

-	uint8_t ParityData    = Byte;

+	/* Calculate the new USART frame data here while while we wait for a previous byte (if any) to finish sending */

+	uint16_t NewUSARTData = ((1 << 11) | (1 << 10) | (0 << 9) | ((uint16_t)Byte << 1) | (0 << 0));

 

 	/* Compute Even parity - while a bit is still set, chop off lowest bit and toggle parity bit */

+	uint8_t ParityData    = Byte;

 	while (ParityData)

 	{

-		EvenParityBit ^= true;

-		ParityData    &= (ParityData - 1);

+		NewUSARTData ^= (1 << 9);

+		ParityData   &= (ParityData - 1);

 	}

 

-	/* Calculate the new USART frame data here while while we wait for a previous byte (if any) to finish sending */

-	uint16_t NewUSARTData = ((1 << 11) | (1 << 10) | ((uint16_t)EvenParityBit << 9) | ((uint16_t)Byte << 1) | (0 << 0));

-

+	/* Wait until transmitter is idle before writing new data */

 	while (SoftUSART_BitCount);

 

 	/* Data shifted out LSB first, START DATA PARITY STOP STOP */

@@ -258,7 +257,7 @@ uint8_t PDITarget_ReceiveByte(void)
 	SoftUSART_BitCount = BITS_IN_FRAME;

 	while (SoftUSART_BitCount);

 	

-	/* Throw away the start, parity and stop bits to leave only the data */

+	/* Throw away the parity and stop bits to leave only the data (start bit is already discarded) */

 	return (uint8_t)SoftUSART_Data;

 #endif

 }

@@ -280,7 +279,7 @@ void PDITarget_SendBreak(void)
 	}

 

 	/* Need to do nothing for a full frame to send a BREAK */

-	for (uint8_t i = 0; i <= BITS_IN_FRAME; i++)

+	for (uint8_t i = 0; i < BITS_IN_FRAME; i++)

 	{

 		/* Wait for a full cycle of the clock */

 		while (PIND & (1 << 5));