I2C-ADS1015.c

/*
 *  Copyright (C) 2023 Swansea University
 *
 *  This file is part of the SELKIELogger suite of tools.
 *
 *  SELKIELogger 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.
 *
 *  SELKIELogger 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 SELKIELogger product.
 *  If not, see <http://www.gnu.org/licenses/>.
*/
 
#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
 
#include <i2c/smbus.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
 
#include "I2C-ADS1015.h"
#include "I2CConnection.h"
 
uint16_t i2c_ads1015_read_configuration(const int busHandle, const int devAddr) {
    if (ioctl(busHandle, I2C_SLAVE, devAddr) < 0) { return false; }
 
    int32_t res = i2c_smbus_read_word_data(busHandle, ADS1015_REG_CONFIG);
    if (res < 0) { return -1; }
    return ((uint16_t)i2c_swapbytes(res));
}
 
float i2c_ads1015_pga_to_scale_factor(const uint16_t config) {
    uint16_t pga = (config & ADS1015_CONFIG_PGA_SELECT);
    if (pga == ADS1015_CONFIG_PGA_6144MV) {
        return 3;
    } else if (pga == ADS1015_CONFIG_PGA_4096MV) {
        return 2;
    } else if (pga == ADS1015_CONFIG_PGA_2048MV) {
        return 1;
    } else if (pga == ADS1015_CONFIG_PGA_1024MV) {
        return 0.5;
    } else if (pga == ADS1015_CONFIG_PGA_0512MV) {
        return 0.25;
    } else if (pga == ADS1015_CONFIG_PGA_0256MV) {
        return 0.125;
    } else if (pga == ADS1015_CONFIG_PGA_0256MV2) {
        return 0.125;
    } else if (pga == ADS1015_CONFIG_PGA_0256MV3) {
        return 0.125;
    } else {
        return NAN;
    }
    return NAN;
}
 
float i2c_ads1015_read_mux(const int busHandle, const int devAddr, const uint16_t mux,
                           const i2c_ads1015_options *opts) {
    if (ioctl(busHandle, I2C_SLAVE, devAddr) < 0) { return NAN; }
 
    uint16_t pga = ADS1015_CONFIG_PGA_DEFAULT;
    float min = -INFINITY;
    float max = INFINITY;
    float scale = 1.0;
    float offset = 0;
 
    if (opts) {
        min = opts->min;
        max = opts->max;
        scale = opts->scale;
        offset = opts->offset;
        pga = opts->pga;
    }
 
    while (!(i2c_ads1015_read_configuration(busHandle, devAddr) & ADS1015_CONFIG_STATE_CONVERT)) {
        usleep(100);
    }
 
    uint16_t confClear = (ADS1015_CONFIG_DEFAULT & ADS1015_CONFIG_MUX_CLEAR & ADS1015_CONFIG_PGA_CLEAR);
    uint16_t muxToSet = (mux & ADS1015_CONFIG_MUX_SELECT);
    uint16_t pgaToSet = (pga & ADS1015_CONFIG_PGA_SELECT);
 
    /*
     * Default configuration with MUX and PGA cleared, OR'd with the MUX
     * bits of mux and PGA bits of pga
     *
     * Finally, the top bit is set (using ADS1015_CONFIG_STATE_CONVERT) to
     * trigger the measurement
     */
    if (i2c_smbus_write_word_data(
            busHandle, ADS1015_REG_CONFIG,
            (uint16_t)i2c_swapbytes(confClear | muxToSet | pgaToSet | ADS1015_CONFIG_STATE_CONVERT)) < 0) {
        return NAN;
    }
    while (i2c_ads1015_read_configuration(busHandle, devAddr) & ADS1015_CONFIG_STATE_CONVERT) {
        usleep(100);
    }
 
    int32_t res = i2c_smbus_read_word_data(busHandle, ADS1015_REG_RESULT);
    if (res < 0) { return NAN; }
 
    uint16_t sres = i2c_swapbytes(res);
    sres = (sres & 0xFFF0) >> 4;
 
    float sv = i2c_ads1015_pga_to_scale_factor(pga);
 
    float adcV = 0;
    if ((sres & 0x800)) {
        uint16_t t = (sres & 0x7FF) + 1;
        adcV = ~t * sv;
    } else {
        adcV = (sres & 0x7FF) * sv;
    }
 
    adcV = scale * adcV + offset;
    if ((adcV < min) || (adcV > max)) { adcV = NAN; }
 
    return adcV;
}
 
float i2c_ads1015_read_ch0(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_SINGLE_0, o);
}
 
float i2c_ads1015_read_ch1(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_SINGLE_1, o);
}
 
float i2c_ads1015_read_ch2(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_SINGLE_2, o);
}
 
 
float i2c_ads1015_read_ch3(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_SINGLE_3, o);
}
 
float i2c_ads1015_read_diff_ch0_ch1(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_DIFF_0_1, o);
}
 
float i2c_ads1015_read_diff_ch0_ch3(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_DIFF_0_3, o);
}
 
float i2c_ads1015_read_diff_ch1_ch3(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_DIFF_1_3, o);
}
 
float i2c_ads1015_read_diff_ch2_ch3(const int busHandle, const int devAddr, const void *opts) {
    i2c_ads1015_options *o = NULL;
    if (opts) { o = (i2c_ads1015_options *)opts; }
    return i2c_ads1015_read_mux(busHandle, devAddr, ADS1015_CONFIG_MUX_DIFF_2_3, o);
}