/* 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; }