67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
#include "twi.h"
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void twi_init() {
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// bitrate = 1600000MHz / (16 + 2 * TWBR * 4^TWPS)
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// Overall prescaler 40 = 16 + 2 * 3 * 4^1
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TWBR = 3; // 2 * 3 = 6
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TWSR |= (1 << TWPS0); // 4
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}
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uint8_t twi_start(void) {
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// Enable internal pull-ups
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PORTC |= (1 << PC5) | (1 << PC4);
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// Setup for sending start condition, trigger sending, keep TWI enabled
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TWCR |= (1 << TWSTA) | (1 << TWINT) | (1 << TWEN);
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// Poll for TWI unit to finish
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while(!(TWCR & (1 << TWINT)));
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// Check if start was succesfull
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return (TW_STATUS != TW_START);
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}
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void twi_stop(void) {
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// Setup for sending stop condition, trigger sending, keep TWI enabled
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TWCR = (1 << TWSTO) | (1 << TWINT) | (1 << TWEN);
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}
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uint8_t twi_write(uint8_t address, uint8_t data[], uint8_t len) {
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// Send start condition
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if(twi_start()) {
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return 1;
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}
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TWDR = (address << 1) | TW_WRITE; // We want to write to the slave
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TWCR = (1 << TWINT) | (1 << TWEN); // Trigger transmission, keep TWI enabled
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// Wait for TWI unit to finish
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while(!(TWCR & (1 << TWINT)));
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// Make sure the slave has acked
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if(TW_STATUS != TW_MT_SLA_ACK) {
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return 1;
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}
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for(uint8_t i = 0; i < len; i++) {
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TWDR = data[i]; // Send actual data
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TWCR = (1 << TWINT ) | (1 << TWEN); // Trigger transmission, keep TWI enabled
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// Wait for TWI unit to finish
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while(!(TWCR & (1 << TWINT)));
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// Make sure the data has been acked
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if(TW_STATUS != TW_MT_DATA_ACK) {
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return 1;
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}
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}
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// Send stop condition
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twi_stop();
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return 0;
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}
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