avr/i2c/i2c.c

/*
Copyright 2022, Savanni D'Gerinel <savanni@luminescent-dreams.com>

This file is part of Savanni's AVR library.

This AVR library 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 3 of the License, or (at your option) any later version.

This AVR library 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 AVR library. If not, see <https://www.gnu.org/licenses/>.
*/

#include <util/delay.h>
#include "i2c.h"

void i2c_delay(void) {
    _delay_us(5);
}

inline void set_sda(i2c_bus_t *bus) {
    dio_set_direction(&bus->sda, LINE_IN);
}

inline void clear_sda(i2c_bus_t *bus) {
    dio_set_direction(&bus->sda, LINE_OUT);
}

inline uint8_t read_sda(i2c_bus_t *bus) {
    return dio_read(&bus->sda);
}

inline void set_scl(i2c_bus_t *bus) {
    dio_set_direction(&bus->scl, LINE_IN);
}

inline void clear_scl(i2c_bus_t *bus) {
    dio_set_direction(&bus->scl, LINE_OUT);
}

inline uint8_t read_scl(i2c_bus_t *bus) {
    return dio_read(&bus->scl);
}

void i2c_init(i2c_bus_t *bus) {
    dio_set(&bus->sda, 0);
    dio_set(&bus->scl, 0);
    set_sda(bus);
    set_scl(bus);
}

void i2c_start_condition(i2c_bus_t *bus, i2c_error_e *error) {
    if (*error != i2c_ok) return;

    // TODO: handle the restart state

    if (read_sda(bus) == 0) {
        *error = i2c_arbitration_lost;
        return;
    }

    clear_sda(bus);
    i2c_delay();
    clear_scl(bus);
}

void i2c_end_condition(i2c_bus_t *bus, i2c_error_e *error) {
    if (*error != i2c_ok) return;

    clear_sda(bus);
    i2c_delay();

    set_scl(bus);

    int count = 0;
    while (read_scl(bus) == 0) {
        if (count == 5) {
            *error = i2c_timeout;
            return;
        }
        count++;
        i2c_delay();
    }

    i2c_delay();

    set_sda(bus);
    i2c_delay();

    if (read_sda(bus) == 0) {
        *error = i2c_arbitration_lost;
    }
}

void i2c_write_bit(i2c_bus_t *bus, uint8_t value, i2c_error_e *error) {
    if (*error != i2c_ok) return;

    if (value) {
        clear_sda(bus);
    } else {
        set_sda(bus);
    }
    i2c_delay();

    set_scl(bus);
    i2c_delay();

    int count = 0;
    while (read_scl(bus) == 0) {
        if (count == 5) {
            *error = i2c_timeout;
            return;
        }
        count++;
        i2c_delay();
    }


    if (value && (read_sda(bus) == 0)) {
        *error = i2c_arbitration_lost;
    }

    clear_scl(bus);
}

uint8_t i2c_read_bit(i2c_bus_t *bus, i2c_error_e *error) {
    uint8_t bit;

    if (*error != i2c_ok) return 0;

    set_sda(bus);
    i2c_delay();

    set_scl(bus);
    int count = 0;
    while (read_scl(bus) == 0) {
        if (count == 5) {
            *error = i2c_timeout;
            return 0;
        }
        count++;
        i2c_delay();
    }
    i2c_delay();

    bit = read_sda(bus);
    clear_scl(bus);
    return bit;
}

void i2c_write_byte(i2c_bus_t *bus, uint8_t value, i2c_error_e *error) {
    if (*error != i2c_ok) return;

    for (int i = 7; i >= 0; i--) {
        i2c_write_bit(bus, value & _BV(i), error);
    }

    uint8_t nak = i2c_read_bit(bus, error);
    if (*error != i2c_ok) return;

    if (nak) {
        *error = i2c_nak;
    }

    return;
}

uint8_t i2c_read_byte(i2c_bus_t *bus, i2c_error_e *error) {
    if (*error != i2c_ok) return 0;

    uint8_t value = 0;
    for (int i = 0; i < 8; i++) {
        value = value << 1 | i2c_read_bit(bus, error);
    }

    if (*error != i2c_ok) {
        i2c_error_e tmp_error;
        i2c_write_bit(bus, 1, &tmp_error);
        return 0;
    }

    i2c_write_bit(bus, 0, error);
    return value;
}

/*
void i2c_host_write(i2c_bus_t *bus, uint8_t address, uint8_t *data, size_t length, i2c_error_e *error) {
    if (*error != i2c_ok) return;

    i2c_host_write_packet(bus, address << 1, error);
    if (*error != ok) return;

    for (int i = 0; i < length; i++) {
        i2c_host_write_packet(bus, data[i], error);
        if (*error != ok) return;
    }
}
*/