Colony » Colony Scout

#include <stdint.h>

#include <avr/io.h>

#include <avr/interrupt.h>

#include <util/delay.h>

#include "tiny-twi.h"

#include "bomi2c.h"

char last_bit;

char count;

uint16_t data;

volatile char currently_sending;

char sending_counter;

uint16_t sending_data;

#define READ_BIT(pin, bit) (((pin) >> bit) & 1)

#define SET_BIT(pin, bit) ((pin) |= (1 << (bit)))

#define CLEAR_BIT(pin, bit) ((pin) &= ~(1 << (bit)))

#define PRESCALAR 8

#define TIME_US(us) (F_CPU * (us) / 1000000 / PRESCALAR)

#define ADDRESS 0x3 

#define DETECT PB3

#define EMIT PB4

#if DETECT == PB3

  #define PCINT_DETECT PCINT3

#endif

#if DETECT == PB4

  #define PCINT_DETECT PCINT4

#endif

static void bom_init(void) {

  SET_BIT(DDRB, EMIT);

  init_detect();

  init_timer1();

  sei();

}

////////////////////////////////// Receiving ///////////////////////////////////

static void init_detect(void) {

  TCCR0A |= _BV(WGM01);    // enable reset on compare A

  TIMSK  |= _BV(OCIE0A);   // enable timer0 compare match A

  OCR0A   = TIME_US(1000); // trigger every 1ms

  GIFR   |= _BV(PCIF);   // Clear any previous detections

  GIMSK  |= _BV(PCIE);   // Enable pin change interrupt for detection

  PCMSK  |= _BV(PCINT_DETECT); // Enable interrupt on detect pin

}

// Disables the interrupt that begins the detect process while it is running

static void disable_detect_interrupt(void) {

  PCMSK &= ~_BV(PCINT_DETECT);

}

static void start_timer0(void) {

  TCNT0 = 0; // Reset timer 0 count to 0

  TCCR0B |= _BV(CS01);     // setup clkio and start the timer

}

static void start_detect(void) {

  disable_detect_interrupt();

  data = 0;

  count = 0;

  last_bit = 0;

  start_timer0();

}

static void restart_detect(void) {

  TCCR0B &= ~0x07; // Stop timer0

  PCMSK  |= _BV(PCINT_DETECT); // Enable interrupt on detect pin

}

ISR(PCINT0_vect) {

  start_detect();

}

ISR(TIMER0_COMPA_vect) {

  char this_bit = READ_BIT(PINB, DETECT);

  if (this_bit == 1) {

    if (last_bit == 1) {

      restart_detect();

    }

  } else {

    data = data << 1 | (last_bit & 1);

    count++;

  }

  last_bit = this_bit;

  if (count == 15) {

    restart_detect();

    smb_send_data((uint8_t*) &data, sizeof(data));

  }

}

////////////////////////////////////////////////////////////////////////////////

//////////////////////////////////// Sending ///////////////////////////////////

static void start_timer1() {

  TCNT1 = 0; // Reset timer 1 count to 0

  TCCR1 |= _BV(CS12); // Set prescalar to 8 and start timer1

}

static void stop_timer1() {

  TCCR1 &= ~0x0F; // Stop the timer without clearing CTC1

}

static void init_timer1() {

  OCR1B = TIME_US(320); // Set match b to fire every 320 us

  TIMSK |= _BV(OCIE1A) | _BV(OCIE1B); // Enable interrupt for match a and b

  TCCR1 |= _BV(CTC1);   // Enables resetting timer1 after matches match c

}

static void send_data(uint16_t data) {

  sending_data = data;

  sending_counter = 0;

  currently_sending = 1;

  SET_BIT(PORTB, EMIT);

  start_timer1();

  send_next_bit();

}

static void send_next_bit() {

  char next_bit = sending_data >> (14 - sending_counter) & 1;

  char ocr_temp = next_bit ? TIME_US(2000) : TIME_US(1000);

  OCR1A = ocr_temp; // Compare A - Turns on transmitter

  OCR1C = ocr_temp; // Reset the timer when match a fires

}

// Compare A - Turns on transmitter

ISR(TIMER1_COMPA_vect) {

  SET_BIT(PORTB, EMIT); 

  sending_counter++;

  send_next_bit();

}

// Compare B - Turns off transmitter after 320us

ISR(TIMER1_COMPB_vect) {

  CLEAR_BIT(PORTB, EMIT);

  if (sending_counter >= 15) {

    currently_sending = 0;

    stop_timer1();

  }

}

////////////////////////////////////////////////////////////////////////////////

static void slave_rx(uint8_t *buf, int len) {

  if (len >= 3) {

    switch (buf[0]) {

      case BOM_I2C_SEND:

        if (!currently_sending) send_data((uint16_t) buf[1] << 8 | buf[2]);  

        break;

    }

  }

}

int main() {

  bom_init();

  smb_init(slave_rx);

  smb_set_address(ADDRESS);

  for (;;);;;;;;;;;;;;;;;;; 

}