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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/>.
+*/
+
+// Please do not modify this file
+
+#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;
+}