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/*
LUFA Library
Copyright (C) Dean Camera, 2009.
dean [at] fourwalledcubicle [dot] com
www.fourwalledcubicle.com
*/
/*
Copyright 2009 David Prentice (david.prentice [at] farming [dot] uk)
Copyright 2009 Peter Danneger
Copyright 2009 Dean Camera (dean [at] fourwalledcubicle [dot] com)
Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that the copyright notice and this
permission notice and warranty disclaimer appear in supporting
documentation, and that the name of the author not be used in
advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
The author disclaim all warranties with regard to this
software, including all implied warranties of merchantability
and fitness. In no event shall the author be liable for any
special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether
in an action of contract, negligence or other tortious action,
arising out of or in connection with the use or performance of
this software.
*/
#include "SoftUART.h"
volatile uint8_t srx_done, stx_count;
volatile uint8_t srx_data, srx_mask, srx_tmp, stx_data;
unsigned char SoftUART_IsReady(void)
{
return !(stx_count);
}
unsigned char SoftUART_TxByte(unsigned char c)
{
while (stx_count);
stx_data = ~c;
stx_count = 10;
return c;
}
unsigned char SoftUART_IsReceived(void)
{
return srx_done;
}
unsigned char SoftUART_RxByte(void)
{
while (!(srx_done));
srx_done = 0;
return srx_data;
}
void SoftUART_Init(void)
{
OCR2B = TCNT2 + 1; // force first compare
TCCR2A = (1 << COM2B1) | (1 << COM2B0); // T1 mode 0
TCCR2B = (1 << FOC2B) | (1 << CS21); // CLK/8, T1 mode 0
TIMSK2 = (1 << OCIE2B); // enable tx and wait for start
EICRA = (1 << ISC01); // -ve edge
EIMSK = (1 << INT0); // enable INT0 interrupt
stx_count = 0; // nothing to send
srx_done = 0; // nothing received
STXPORT |= 1 << STX; // TX output
STXDDR |= 1 << STX; // TX output
SRXPORT |= (1 << SRX); // pullup on INT0
}
/* ISR to detect the start of a bit being sent from the transmitter. */
ISR(INT0_vect)
{
OCR2A = TCNT2 + (BIT_TIME / 8 * 3 / 2); // scan 1.5 bits after start
srx_tmp = 0; // clear bit storage
srx_mask = 1; // bit mask
TIFR2 = (1 << OCF2A); // clear pending interrupt
if (!(SRXPIN & (1 << SRX))) // still low
{
TIMSK2 = (1 << OCIE2A) | (1 << OCIE2B); // wait for first bit
EIMSK &= ~(1 << INT0);
}
}
/* ISR to manage the reception of bits to the transmitter. */
ISR(TIMER2_COMPA_vect)
{
if (srx_mask)
{
if (SRXPIN & (1 << SRX))
srx_tmp |= srx_mask;
srx_mask <<= 1;
OCR2A += BIT_TIME / 8; // next bit slice
}
else
{
srx_done = 1; // mark rx data valid
srx_data = srx_tmp; // store rx data
TIMSK2 = (1 << OCIE2B); // enable tx and wait for start
EIMSK |= (1 << INT0); // enable START irq
EIFR = (1 << INTF0); // clear any pending
}
}
/* ISR to manage the transmission of bits to the receiver. */
ISR(TIMER2_COMPB_vect)
{
OCR2B += BIT_TIME / 8; // next bit slice
if (stx_count)
{
if (--stx_count != 9) // no start bit
{
if (!(stx_data & 1)) // test inverted data
TCCR2A = (1 << COM2B1) | (1 << COM2B0);
else
TCCR2A = (1 << COM2B1);
stx_data >>= 1; // shift zero in from left
}
else
{
TCCR2A = (1 << COM2B1); // START bit
}
}
}
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