microphone_adc.c

/**
 * Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"
#include "hardware/adc.h"
#include "hardware/uart.h"
#include "pico/binary_info.h"

/* Example code to extract analog values from a microphone using the ADC
   with accompanying Python file to plot these values

   Connections on Raspberry Pi Pico board, other boards may vary.

   GPIO 26/ADC0 (pin 31)-> AOUT or AUD on microphone board
   3.3v (pin 36) -> VCC on microphone board
   GND (pin 38)  -> GND on microphone board
*/

#define ADC_NUM 0
#define ADC_PIN (26 + ADC_NUM)
#define ADC_VREF 3.3
#define ADC_RANGE (1 << 12)
#define ADC_CONVERT (ADC_VREF / (ADC_RANGE - 1))

int main() {
    stdio_init_all();
    printf("Beep boop, listening...\n");

    bi_decl(bi_program_description("Analog microphone example for Raspberry Pi Pico")); // for picotool
    bi_decl(bi_1pin_with_name(ADC_PIN, "ADC input pin"));

    adc_init();
    adc_gpio_init( ADC_PIN);
    adc_select_input( ADC_NUM);

    uint adc_raw;
    while (1) {
        adc_raw = adc_read(); // raw voltage from ADC
        printf("%.2f\n", adc_raw * ADC_CONVERT);
        sleep_ms(10);
    }

    return 0;
}