// Read analog values from Linux IIO device
//
// Copyright (C) 2017  Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.

#include <fcntl.h> // open
#include <stdio.h> // snprintf
#include <stdlib.h> // atoi
#include <unistd.h> // read
#include "command.h" // shutdown
#include "gpio.h" // gpio_adc_setup
#include "internal.h" // report_errno
#include "sched.h" // sched_shutdown

// ODROID-C5
DECL_CONSTANT("ADC_MAX", 1800);

#define ANALOG_START (1<<12)

DECL_ENUMERATION_RANGE("pin", "analog0", ANALOG_START, 8);

// ODROID-C5
#define IIO_PATH "/sys/bus/iio/devices/iio:device0/in_voltage0_raw"
#define SCALE_PATH "/sys/bus/iio/devices/iio:device0/in_voltage_scale"
#define OFFSET_PATH "/sys/bus/iio/devices/iio:device0/in_voltage_offset"

struct gpio_adc
gpio_adc_setup(uint32_t pin)
{
    struct gpio_adc g;
	int fd;
    char buf[64];
    int ret;

	fd = open(SCALE_PATH, O_RDONLY);
    ret = read(fd, buf, sizeof(buf)-1);
    if (ret <= 0) {
        goto fail;
    }
    buf[ret] = '\0';
    g.scale = atof(buf) * 1000;
    close(fd);

    fd = open(OFFSET_PATH, O_RDONLY);
    ret = read(fd, buf, sizeof(buf)-1);
    if (ret <= 0) {
        goto fail;
    }
    buf[ret] = '\0';
    g.offset = atoi(buf);
    close(fd);

    fd = open(IIO_PATH, O_RDONLY|O_CLOEXEC);
    if (fd < 0) {
        report_errno("analog open", fd);
        goto fail;
    }
    ret = set_non_blocking(fd);
    if (ret < 0)
        goto fail;

    g.fd = fd;
    return g;
fail:
    if (fd >= 0)
        close(fd);
    shutdown("Unable to open adc device");
}

uint32_t
gpio_adc_sample(struct gpio_adc g)
{
    return 0;
}

uint16_t
gpio_adc_read(struct gpio_adc g)
{
    char buf[64];
    int voltage;
    int ret = pread(g.fd, buf, sizeof(buf)-1, 0);
    if (ret <= 0) {
        report_errno("analog read", ret);
        try_shutdown("Error on analog read");
        return 0;
    }
    buf[ret] = '\0';

	voltage = atoi(buf) + g.offset;
	voltage = voltage > 0 ? voltage : 0;
	voltage = voltage * g.scale;
	voltage = voltage < 1800000 ? voltage : 1800000;
	voltage /= 1000;

    return voltage;
}

void
gpio_adc_cancel_sample(struct gpio_adc g)
{
}