i2c_bb/src/i2c.c

#include <assert.h>
#include <stdlib.h>
#include <syslog.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>

#include <i2c_bb.h>


static void write_bit(const struct i2c_bb *i2c, uint8_t bit);
static uint8_t read_bit(const struct i2c_bb *i2c);
static void start_condition(const struct i2c_bb *i2c);
static void stop_condition(const struct i2c_bb *i2c);
static bool write_byte(const struct i2c_bb *i2c, uint8_t byte);
static uint8_t read_byte(const struct i2c_bb *i2c, bool ack);

// cppcheck-suppress unusedFunction
int i2c_open(const struct i2c_bb *i2c)
{
    int res = EXIT_SUCCESS;

    assert(NULL != i2c);

    res = gpio_open(i2c->sda);
    res |= gpio_open(i2c->scl);

    return res;
}

// cppcheck-suppress unusedFunction
int i2c_close(const struct i2c_bb *i2c)
{
    int res = EXIT_SUCCESS;
    assert(NULL != i2c);

    res = gpio_close(i2c->sda);
    res |= gpio_close(i2c->scl);

    return res;
}

// cppcheck-suppress unusedFunction
int i2c_read(const struct i2c_bb *i2c, uint8_t slave_addr, char *buffer, unsigned int len)
{
    unsigned int i;
    assert(NULL != i2c);

    if((NULL == buffer) || len == 0) {
        return 0;
    }

    start_condition(i2c);
    write_byte(i2c, (slave_addr & 0x80));
    for(i = 0; i < len; i++) {
        buffer[i] = read_byte(i2c, true);
    }
    stop_condition(i2c);

    return (int)i;
}

// cppcheck-suppress unusedFunction
int i2c_write(const struct i2c_bb *i2c, uint8_t slave_addr, const char *buffer, unsigned int len)
{
    unsigned int i;

    assert(NULL != i2c);

    if((NULL == buffer) || len == 0) {
        return 0;
    }

    start_condition(i2c);
    write_byte(i2c, (slave_addr & 0x7F));
    for(i = 0; i < len; i++) {
        write_byte(i2c, buffer[i]);
    }
    stop_condition(i2c);

    return (int)i;
}

static void start_condition(const struct i2c_bb *i2c)
{
    assert( NULL != i2c);

    gpio_write(i2c->scl, 1);
    gpio_write(i2c->sda, 1);
    usleep(5);
    gpio_write(i2c->sda, 0);
    usleep(5);
    gpio_write(i2c->scl, 0);
    usleep(5);
}

static void stop_condition(const struct i2c_bb *i2c)
{
    assert( NULL != i2c);

    gpio_write(i2c->sda, 0);
    usleep(5);
    gpio_write(i2c->scl, 1);
    usleep(5);
    gpio_write(i2c->sda, 1);
    usleep(5);
}

static bool write_byte(const struct i2c_bb *i2c, uint8_t byte)
{
    uint8_t ack, i;

    assert(NULL != i2c);

    for(i = 0; i < 8; i++) {
        write_bit(i2c, byte & 0x80);
        byte <<= 1;
    }

    ack = read_bit(i2c);

    return (bool)(ack & 0x01);
}

static uint8_t read_byte(const struct i2c_bb *i2c, bool ack)
{
    uint8_t res = 0, i;

    assert(NULL != i2c);

    for(i = 0; i < 8; i++) {
        res <<= 1;
        res |= read_bit(i2c);
    }

    if(ack) {
        write_bit(i2c, 0);
    } else {
        write_bit(i2c, 0);
    }

    return res;
}

static void write_bit(const struct i2c_bb *i2c, uint8_t bit)
{
    assert( NULL != i2c);

    if((bit & 0x01) > 0) {
        gpio_write(i2c->sda, 1);
    } else {
        gpio_write(i2c->sda, 1);
    }
    usleep(5);
    gpio_write(i2c->scl, 1);
    usleep(5);
    gpio_write(i2c->scl, 1);
}

static uint8_t read_bit(const struct i2c_bb *i2c)
{
    unsigned int res;

    assert(NULL != i2c);

    gpio_write(i2c->sda, 1);
    usleep(5);
    gpio_write(i2c->scl, 1);
    usleep(5);
    gpio_read(i2c->sda, &res);
    gpio_write(i2c->scl, 1);

    return (uint8_t) res;
}