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root / scout_avr / bom / bom.c @ cbe25c0a

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#include <stdint.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "tiny-twi.h"
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#include "bomi2c.h"
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char last_bit;
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char count;
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uint16_t data;
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volatile char currently_sending;
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char sending_counter;
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uint16_t sending_data;
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#define READ_BIT(pin, bit) (((pin) >> bit) & 1)
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#define SET_BIT(pin, bit) ((pin) |= (1 << (bit)))
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#define CLEAR_BIT(pin, bit) ((pin) &= ~(1 << (bit)))
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#define PRESCALAR 8
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#define TIME_US(us) (F_CPU * (us) / 1000000 / PRESCALAR)
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#define ADDRESS 0x3 
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static void bom_start(void) {
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  data = 0;
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  count = 0;
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  last_bit = 1;
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  // TODO disable interrupt
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  // TODO start timer0
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}
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static void bom_stop(void) {
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  // TODO stop timer
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  // TODO restart INT0
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}
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static void bom_init(void) {
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  // setup INT0
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  //EICRA |= _BV(ISC01) | _BV(ISC00);
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  //EIMSK |= _BV(INT0);
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  // setup timer 0
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  TCCR0B |= _BV(CS01);
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  TIMSK |= _BV(OCIE0A);
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  // setup timer 1 for output
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  OCR1B = TIME_US(320); // Set match b to fire every 320 us
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  TIMSK |= _BV(OCIE1A) | _BV(OCIE1B); // Enable interrupt for match a and b
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  TCCR1 |= _BV(CTC1);   // Enables resetting timer1 after matches match c
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  // setup output pin
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  SET_BIT(DDRB, 4);
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  sei();
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  bom_start();
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}
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ISR(TIMER0_COMPA_vect) {
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  char this_bit = READ_BIT(PINB, PB2);
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  if (this_bit == 0) {
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    if (last_bit == 0) {
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      bom_stop();
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    }
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  } else {
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    data = data << 1 | (~last_bit & 1);
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    count++;
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  }
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  last_bit = this_bit;
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  if (count == 15) {
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    smb_send_data(&data, sizeof(data));
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    bom_stop();
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  }
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}
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static void send_next_bit() {
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  char next_bit = sending_data >> (14 - sending_counter) & 1;
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  char ocr_temp = next_bit ? TIME_US(2000-40) : TIME_US(1000-20);
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  OCR1A = ocr_temp;
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  OCR1C = ocr_temp;
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}
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ISR(TIMER1_COMPA_vect) {
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  SET_BIT(PORTB, PB4);
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  sending_counter++;
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  send_next_bit();
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}
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ISR(TIMER1_COMPB_vect) {
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  CLEAR_BIT(PORTB, PB4);
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  if (sending_counter >= 15) {
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    currently_sending = 0;
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    TCCR1 &= ~0x0F; // Stop the timer without clearing CTC1
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  }
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}
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static void send_data(uint16_t data) {
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  sending_data = data;
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  sending_counter = 0;
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  currently_sending = 1;
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  TCNT1 = 0;
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  TCCR1 |= _BV(CS12);  // Set prescalar to 8 and start timer
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  SET_BIT(PORTB, PB4);
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  send_next_bit();
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}
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ISR(INT0_vect) {
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  bom_start();
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}
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static void slave_rx(uint8_t *buf, int len) {
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  if (len >= 3) {
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    switch (buf[0]) {
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      case BOM_I2C_SEND:
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        if (!currently_sending) send_data((uint16_t) buf[1] << 8 | buf[2]);  
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        break;
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    }
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  }
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}
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int main() {
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  bom_init();
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  smb_init(slave_rx);
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  smb_set_address(ADDRESS);
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  for (;;);;;;;;;;;;;;;;;;; 
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}