/**
 * To configure a PWM signal at 20 Hz with a 50% duty cycle
 * on GP2 and feed it into an ADC at GP26 while
 * sampling the ADC every 25 ms,
 * you must use the Raspberry Pi Pico and its Pico C SDK.
 *
 * You will need to use a jumper wire to connect GP2 to GP26.
 * You may use a timer interrupt.
 */

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/pwm.h"
#include "hardware/adc.h"

#define PWM_PIN 2
#define PWM_FREQ 20
#define PWM_DUTY 0.5

#define ADC_PIN 26
#define ADC_FREQ 25

void setup () {
    gpio_set_function(PWM_PIN, GPIO_FUNC_PWM);
    uint slice_num = pwm_gpio_to_slice_num(PWM_PIN);

    pwm_set_wrap(slice_num, 100);
    // Setup PWM with 20 Hz frequency and 50% duty cycle
    pwm_set_chan_level(slice_num, PWM_CHAN_A, PWM_DUTY * 100);
    pwm_set_enabled(slice_num, true);
    pwm_set_clkdiv(slice_num, 1);

    // Set up ADC
    adc_init();
    adc_gpio_init(ADC_PIN);
    adc_select_input(0);
}

bool repeating_timer_callback (struct repeating_timer *t) {
    // Read ADC value
    uint16_t result = adc_read();
    uint64_t time = time_us_64();
    printf("%02d:%02d:%02d:%03d -> ADC value: %d\n",
           (int) (time / 3600000000),
           (int) (time / 60000000) % 60,
           (int) (time / 1000000) % 60,
           (int) (time / 1000) % 1000,
           result
    );

    return true;
}

int main () {
    stdio_init_all();
    setup();

    struct repeating_timer timer;

    // Setup timer interrupt
    add_repeating_timer_ms(ADC_FREQ,
                           repeating_timer_callback,
                           NULL,
                           &timer
    );

    while (true)
    {
        tight_loop_contents();
    }
}