sensirion_i2c_hal.c

/*
 * Copyright (c) 2018, Sensirion AG
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * * Neither the name of Sensirion AG nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/* Enable usleep function */
#define _DEFAULT_SOURCE

#include "sensirion_i2c_hal.h"
#include "sensirion_common.h"
#include "sensirion_config.h"

#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>

/**
 * The following define was taken from i2c-dev.h. Alternatively the header file
 * can be included. The define was added in Linux v3.10 and never changed since
 * then.
 */
#define I2C_SLAVE 0x0703

#define I2C_WRITE_FAILED -1
#define I2C_READ_FAILED -1

static int i2c_device = -1;
static uint8_t i2c_address = 0;

/**
 * Initialize all hard- and software components that are needed for the I2C
 * communication.
 */
void sensirion_i2c_hal_init(const char* device_path) {
    /* open i2c adapter */
    i2c_device = open(device_path, O_RDWR);
    if (i2c_device == -1)
        return; /* no error handling */
}

/**
 * Release all resources initialized by sensirion_i2c_hal_init().
 */
void sensirion_i2c_hal_free(void) {
    if (i2c_device >= 0)
        close(i2c_device);
}

/**
 * Execute one read transaction on the I2C bus, reading a given number of bytes.
 * If the device does not acknowledge the read command, an error shall be
 * returned.
 *
 * @param address 7-bit I2C address to read from
 * @param data    pointer to the buffer where the data is to be stored
 * @param count   number of bytes to read from I2C and store in the buffer
 * @returns 0 on success, error code otherwise
 */
int8_t sensirion_i2c_hal_read(uint8_t address, uint8_t* data, uint16_t count) {
    if (i2c_address != address) {
        ioctl(i2c_device, I2C_SLAVE, address);
        i2c_address = address;
    }

    if (read(i2c_device, data, count) != count) {
        return I2C_READ_FAILED;
    }
    return 0;
}

/**
 * Execute one write transaction on the I2C bus, sending a given number of
 * bytes. The bytes in the supplied buffer must be sent to the given address. If
 * the slave device does not acknowledge any of the bytes, an error shall be
 * returned.
 *
 * @param address 7-bit I2C address to write to
 * @param data    pointer to the buffer containing the data to write
 * @param count   number of bytes to read from the buffer and send over I2C
 * @returns 0 on success, error code otherwise
 */
int8_t sensirion_i2c_hal_write(uint8_t address, const uint8_t* data,
                               uint16_t count) {
    if (i2c_address != address) {
        ioctl(i2c_device, I2C_SLAVE, address);
        i2c_address = address;
    }

    if (write(i2c_device, data, count) != count) {
        return I2C_WRITE_FAILED;
    }
    return 0;
}

/**
 * Sleep for a given number of microseconds. The function should delay the
 * execution for at least the given time, but may also sleep longer.
 *
 * @param useconds the sleep time in microseconds
 */
void sensirion_i2c_hal_sleep_usec(uint32_t useconds) {
    usleep(useconds);
}