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/*
Copyright 2016 Luiz Ribeiro <luizribeiro@gmail.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <avr/io.h>
#include <util/twi.h>
#include "i2c.h"
void i2c_set_bitrate(uint16_t bitrate_khz) {
uint8_t bitrate_div = ((F_CPU / 1000l) / bitrate_khz);
if (bitrate_div >= 16) {
bitrate_div = (bitrate_div - 16) / 2;
}
TWBR = bitrate_div;
}
void i2c_init(void) {
// set pull-up resistors on I2C bus pins
PORTC |= 0b11;
i2c_set_bitrate(400);
// enable TWI (two-wire interface)
TWCR |= (1 << TWEN);
// enable TWI interrupt and slave address ACK
TWCR |= (1 << TWIE);
TWCR |= (1 << TWEA);
}
uint8_t i2c_start(uint8_t address) {
// reset TWI control register
TWCR = 0;
// begin transmission and wait for it to end
TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)));
// check if the start condition was successfully transmitted
if ((TWSR & 0xF8) != TW_START) {
return 1;
}
// transmit address and wait
TWDR = address;
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)));
// check if the device has acknowledged the READ / WRITE mode
uint8_t twst = TW_STATUS & 0xF8;
if ((twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK)) {
return 1;
}
return 0;
}
void i2c_stop(void) {
TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
}
uint8_t i2c_write(uint8_t data) {
TWDR = data;
// transmit data and wait
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)));
if ((TWSR & 0xF8) != TW_MT_DATA_ACK) {
return 1;
}
return 0;
}
uint8_t i2c_send(uint8_t address, uint8_t *data, uint16_t length) {
if (i2c_start(address)) {
return 1;
}
for (uint16_t i = 0; i < length; i++) {
if (i2c_write(data[i])) {
return 1;
}
}
i2c_stop();
return 0;
}
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