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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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// Please do not modify this file |
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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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} |