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// Copyright (C) 2009 Onno Kortmann <onno@gmx.net>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA..
//
//-----------------------------------------------------------------------------
//
// IMPORTANT NOTE: This file is only to illustrate the simulavrxx<->verilog
// interface and is by no means any reference for anything whatsoever! It
// probably contains lots of bugs! As already stated above, there is no
// warranty!
//
//-----------------------------------------------------------------------------
#include <avr/io.h>
#include <avr/interrupt.h>
#include "csinglepincomm.h"
#define F_CPU 12000000
// Port definition for SPC
// NOTE: DO NOT CHANGE THESE EASILY, THE TIMER OUTPUT PINS ARE USED
// SO CHANGING THE PINS IS USUALLY NOT AN OPTION!
#define SPC_PORT PORTB
#define SPC_DDR DDRB
#define SPC_PIN PINB
#define SPC_BIT PB3
// Constant to delay the short delay (t_s), initial value. In clock ticks */
#define SPC_INITIAL_DELAY 1500
// Initial multiplier N to go from t_s to t_l: t_l=N*t_s */
#define SPC_LONG_DELAY 3
// loop cycles to wait for receive signal
#define SPC_RX_TIMEOUT 20000
// minimum distance between the high and the low count, in number of counts of
// the smaller value
#define SPC_MINIMUM_DISTANCE 2
// Interrupt blocking?
#if SPC_CLISEI
#define NCLI cli()
#define NSEI sei()
#else
#define NCLI
#define NSEI
#endif
uint16_t spc_delay=SPC_INITIAL_DELAY;
uint8_t spc_multiplier=SPC_LONG_DELAY;
uint8_t spc_mindistance=SPC_MINIMUM_DISTANCE;
void spc_init() {
// enable pull up
SPC_PORT|=_BV(SPC_BIT);
}
uint8_t spc_trx_bit(uint8_t bit) {
uint16_t timeout, high_time, low_time;
uint16_t spc_long_delay=spc_delay * spc_multiplier;
// ------------------------------------------------------------
// --- TRANSMIT ---
// ------------------------------------------------------------
NCLI;
TCCR1B=0; // stop counter
// timer preparation
// force compare-match into high state
TCCR1A=_BV(COM1A1)|_BV(COM1A0); // set PB3 on compare match
TCCR1C=_BV(FOC1A); // force output compare
// set high state of comp.match on output (should be just pullup before)
SPC_DDR|=_BV(SPC_BIT);
TCCR1A=_BV(COM1A1); // clear PB3 on compare match
TIFR|=_BV(OCF1A); // clear comp.match
// set time until zero
if (bit)
OCR1A=spc_long_delay;
else
OCR1A=spc_delay;
// reset counter
TCNT1=0;
// and apply full system clock timer1
TCCR1B=_BV(CS10);
NSEI;
// wait until high part has been sent
while (! (TIFR & _BV(OCF1A)));
NCLI;
TCCR1B=0; // stop counter
TCCR1A=_BV(COM1A1)|_BV(COM1A0); // set PB3 on compare match
TIFR|=_BV(OCF1A); // clear comp.match
// set time until one
if (bit)
OCR1A=spc_delay;
else
OCR1A=spc_long_delay;
// reset counter
TCNT1=0;
TCCR1B=_BV(CS10); // start counter
NSEI;
// wait until low part has been sent
while (! (TIFR & _BV(OCF1A)));
NCLI;
//TIFR|=_BV(OCF1A); // clear comp.match
// ------------------------------------------------------------
// --- RECEIVE ---
// ------------------------------------------------------------
// go back to normal port mode on PB3
TCCR1A=0;
SPC_DDR&=~_BV(SPC_BIT);
OCR1A=0x0000; // 'disable' OCR1A
NSEI;
/* stop and clear counter, set noise canceler bit,
get ready for input capture. */
TCNT1=0;
TIFR|=_BV(ICF1);
TCCR1B=_BV(CS10)|_BV(ICNC1);
NSEI;
// wait for falling edge
timeout=0;
while (! (TIFR & _BV(ICF1))) {
if (timeout == SPC_RX_TIMEOUT)
return 2;
timeout++;
}
NCLI;
high_time=ICR1; // read that value
// get ready for another round, raising edge now
TCCR1B=_BV(CS10)|_BV(ICNC1)|_BV(ICES1);
TIFR|=_BV(ICF1);
NSEI;
// wait for rising edge
timeout=0;
while (! (TIFR & _BV(ICF1))) {
if (timeout == SPC_RX_TIMEOUT)
return 2;
timeout++;
}
NCLI;
low_time=ICR1-high_time; // read that value, too
NSEI;
if (high_time>low_time) {
if (high_time<low_time * spc_mindistance)
return 2;
else return 1;
} else {
if (low_time<high_time * spc_mindistance)
return 2;
else return 0;
}
}
uint16_t spc_trx(uint8_t val) {
uint8_t res;
uint8_t i;
uint8_t rxbit;
// send start bit
i=spc_trx_bit(0);
if (i) // timeout or 'one' bit?
return 0x100 * i;
// main TRX loop
res=0;
for (i=0; i < 8; i++) {
rxbit=spc_trx_bit(val & 0x01);
if (rxbit>1)
return 0x100 * rxbit; // timeout or framing error!
if (rxbit) res|=1<<i;
val>>=1;
}
return res;
}
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