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

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This commit is contained in:
Dean Camera 2009-12-16 09:13:42 +00:00
parent f0b4d79629
commit 021b1b567e
5 changed files with 25 additions and 38 deletions
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17
Projects/AVRISP/Lib/PDITarget.c
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@ -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));