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root / scout_avr / bom / bom.c @ 1b05b4cc

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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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#define DETECT PB3
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#define EMIT PB4
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#if DETECT == PB3
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  #define PCINT_DETECT PCINT3
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#endif
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#if DETECT == PB4
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  #define PCINT_DETECT PCINT4
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#endif
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static void bom_init(void) {
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  init_detect();
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  init_timer1();
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  sei();
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}
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////////////////////////////////// Receiving ///////////////////////////////////
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static void init_detect(void) {
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  TCCROA |= _BV(WGM01);    // enable reset on compare A
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  TIMSK  |= _BV(OCIE0A);   // enable timer0 compare match A
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  GIMSK  |= _BV(PCIE);   // Enable pin change interrupt for detection
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  PCMSK  |= _BV(PCINT_DETECT); // Enable interrupt on detect pin
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}
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// Disables the interrupt that begins the detect process while it is running
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static void disable_detect_interrupt(void) {
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  PCMSK &= ~_BV(PCINT_DETECT);
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}
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static void start_timer0(void) {
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  TCNT0 = 0; // Reset timer 0 count to 0
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  TCCR0B |= _BV(CS01);     // setup clkio and start the timer
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}
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static void start_detect(void) {
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  disable_detect_interrupt();
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  data = 0;
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  count = 0;
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  last_bit = 1;
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  start_timer0();
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}
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static void restart_detect(void) {
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  TCCR0B &= ~0x07; // Stop timer0
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  PCMSK  |= _BV(PCINT_DETECT); // Enable interrupt on detect pin
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}
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ISR(PCINT0_vect) {
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  start_detect();
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}
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ISR(TIMER0_COMPA_vect) {
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  char this_bit = READ_BIT(PINB, DETECT);
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  if (this_bit == 0) {
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    if (last_bit == 0) {
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      restart_detect();
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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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    restart_detect();
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    smb_send_data(&data, sizeof(data));
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  }
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}
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////////////////////////////////////////////////////////////////////////////////
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//////////////////////////////////// Sending ///////////////////////////////////
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static void start_timer1() {
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  TCNT1 = 0; // Reset timer 1 count to 0
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  TCCR1 |= _BV(CS12) // Set prescalar to 8 and start timer1
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}
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static void stop_timer1() {
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  TCCR1 &= ~0x0F; // Stop the timer without clearing CTC1
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}
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static void init_timer1() {
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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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}
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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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  SET_BIT(PORTB, EMIT);
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  start_timer1();
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  send_next_bit();
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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; // Compare A - Turns on transmitter
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  OCR1C = ocr_temp; // Reset the timer when match a fires
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}
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// Compare A - Turns on transmitter
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ISR(TIMER1_COMPA_vect) {
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  SET_BIT(PORTB, EMIT); 
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  sending_counter++;
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  send_next_bit();
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}
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// Compare B - Turns off transmitter after 320us
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ISR(TIMER1_COMPB_vect) {
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  CLEAR_BIT(PORTB, EMIT);
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  if (sending_counter >= 15) {
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    currently_sending = 0;
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    stop_timer1();
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  }
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}
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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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}