/*ADC channel 3 reads the internal VSYS voltage through a built-in 1/3 voltage divider.

The raw ADC value (0-4095) converts to an internal voltage between 0V and 3.3V.

Multiply by 3 to get the actual VSYS supply voltage.

GPIO29 is not exposed externally; this input is internal only.

Use this to monitor the board’s input power voltage programmatically.*/

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

int main() {
    stdio_init_all();

    adc_init();
    // GPIO29 is ADC input 3 (VSYS voltage monitor) - not physically exposed
    adc_select_input(3);

    while (true) {
        uint16_t raw = adc_read();

        // Convert ADC reading to voltage - scale depends on internal divider
        // VSYS voltage connected via 1/3 voltage divider internally
        float vsys_voltage = (raw * 3.3f / 4095) * 3;

        printf("Raw ADC: %d, VSYS Voltage: %.3f V\n", raw, vsys_voltage);

        sleep_ms(1000);
    }
}