ahoneybun/qmk_firmware
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Major changes to the XPLAINBridge software UART code for performance and reliability. New code reduces the number of missed characters and misread characters.

Browse source
This commit is contained in:
Dean Camera 2010-07-11 14:14:08 +00:00
parent 2b0d93c129
commit 229935184b
4 changed files with 61 additions and 55 deletions
Download patch file Download diff file Expand all files Collapse all files

94
Projects/XPLAINBridge/Lib/SoftUART.c
View file

@ -45,8 +45,8 @@ static uint8_t TX_BitsRemaining;
/** Temporary data variable to hold the byte being transmitted as it is shifted out */
static uint8_t TX_Data;
/** Current bit mask of the bit being shifted into the received data byte */
static uint8_t RX_BitMask;
/** Total number of bits remaining to be received in the current frame */
static uint8_t RX_BitsRemaining;
/** Temporary data variable to hold the byte being received as it is shifted in */
static uint8_t RX_Data;
@ -63,89 +63,83 @@ void SoftUART_Init(void)
EICRA = (1 << ISC01);
EIMSK = (1 << INT0);
/* Start software UART transmission and reception timers */
/* Set reception timer compare period and enable compare ISR */
OCR1A = BIT_TIME;
TIMSK1 = (1 << OCIE1A);
/* Set transmission timer compare period, enable compare ISR and start the timer */
OCR3A = BIT_TIME;
TIMSK3 = (1 << OCIE3A);
TCCR3B = (1 << CS30);
TCCR1B = (1 << CS10);
TCCR3B = ((1 << CS30) | (1 << WGM32));
}
/** ISR to detect the start of a bit being sent to the software UART. */
ISR(INT0_vect, ISR_BLOCK)
{
/* Set reception channel to fire 1.5 bits past the beginning of the start bit */
OCR1A = TCNT1 + (BIT_TIME + (BIT_TIME / 2));
/* Reset and start the reception timer */
TCNT1 = 0;
TCCR1B = ((1 << CS10) | (1 << WGM12));
/* Clear the received data temporary variable, reset the current received bit position mask */
RX_Data = 0;
RX_BitMask = (1 << 0);
/* Clear reception channel ISR flag and enable the bit reception ISR */
TIFR1 = (1 << OCF1A);
TIMSK1 = (1 << OCIE1A);
/* Reset the number of reception bits remaining counter */
RX_BitsRemaining = 8;
/* Disable start bit detection ISR while the next byte is received */
EIMSK &= ~(1 << INT0);
EIMSK = 0;
}
/** ISR to manage the reception of bits to the software UART. */
ISR(TIMER1_COMPA_vect, ISR_BLOCK)
{
/* Move the reception ISR compare position one bit ahead */
OCR1A += BIT_TIME;
/* Cache the current RX pin value for later checking */
uint8_t SRX_Cached = (SRXPIN & (1 << SRX));
/* Check if reception has finished */
if (RX_BitMask)
if (RX_BitsRemaining)
{
/* Store next bit into the received data variable */
if (SRXPIN & (1 << SRX))
RX_Data |= RX_BitMask;
/* Shift the current received bit mask to the next bit position */
RX_BitMask <<= 1;
RX_Data >>= 1;
RX_BitsRemaining--;
/* Store next bit into the received data variable */
if (SRX_Cached)
RX_Data |= (1 << 7);
}
else
{
/* Reception complete, store the received byte */
RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
/* Disable the reception ISR as all data has now been received, re-enable start bit detection ISR */
TIMSK1 = 0;
/* Disable the reception timer as all data has now been received, re-enable start bit detection ISR */
TCCR1B = 0;
EIFR = (1 << INTF0);
EIMSK = (1 << INT0);
/* Reception complete, store the received byte if stop bit valid */
if (SRX_Cached)
RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
}
}
/** ISR to manage the transmission of bits via the software UART. */
ISR(TIMER3_COMPA_vect, ISR_NOBLOCK)
{
/* Move the transmission ISR compare position one bit ahead */
OCR3A += BIT_TIME;
/* Check if transmission has finished */
if (TX_BitsRemaining)
{
/* Check if we are sending a data bit, or the start bit */
if (--TX_BitsRemaining != 9)
{
/* Set the TX line to the value of the next bit in the byte to send */
if (TX_Data & (1 << 0))
STXPORT &= ~(1 << STX);
else
STXPORT |= (1 << STX);
/* Shift the transmission byte to move the next bit into position */
TX_Data >>= 1;
}
/* Set the TX line to the value of the next bit in the byte to send */
if (TX_Data & (1 << 0))
STXPORT &= ~(1 << STX);
else
{
/* Start bit - keep TX line low */
STXPORT &= ~(1 << STX);
}
STXPORT |= (1 << STX);
/* Shift the transmission byte to move the next bit into position and decrement the bits remaining counter */
TX_Data >>= 1;
TX_BitsRemaining--;
}
else if (USBtoUART_Buffer.Count)
{
/* Start bit - TX line low */
STXPORT &= ~(1 << STX);
/* Transmission complete, get the next byte to send (if available) */
TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
TX_BitsRemaining = 10;
TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
TX_BitsRemaining = 9;
}
}
}