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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} |