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