From 021b1b567e8686d4addccb53511b7f5447392267 Mon Sep 17 00:00:00 2001 From: Dean Camera Date: Wed, 16 Dec 2009 09:13:42 +0000 Subject: More speed and quality improvements to the software USART in the AVRISP project. --- Projects/AVRISP/Lib/PDITarget.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) (limited to 'Projects/AVRISP/Lib/PDITarget.c') 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)); -- cgit v1.2.3