adc-voltmeter

Single-shot ADC sample on ALP_E1M_ADC0 converted to millivolts. The minimal demo for <alp/adc.h>.

Source: examples/adc-voltmeter/.

board.yaml

som:
  sku: E1M-AEN701

preset: e1m-evk

cores:
  m55_hp:
    app: ./src
    peripherals: [adc]

diagnostics:
  log_level: info

Source (abbreviated)

#include <alp/adc.h>
#include <alp/e1m_pinout.h>

int main(void) {
    alp_adc_t *adc = alp_adc_open(&(alp_adc_config_t){
        .channel_id      = ALP_E1M_ADC0,
        .resolution_bits = 12,
        .reference       = ALP_ADC_REF_INTERNAL,
    });
    if (adc == NULL) {
        printk("[adc] open failed: err=%d\n", (int)alp_last_error());
        return -1;
    }

    int32_t raw = 0;
    alp_adc_read_raw(adc, &raw);
    uint32_t millivolts = ((uint32_t)raw * 3300u) / ((1u << 12) - 1u);
    printk("[adc] raw=%d  mV=%u\n", raw, millivolts);

    alp_adc_close(adc);
    return 0;
}

Expected output

[adc] raw=2048  mV=1650

Mid-scale on a 12-bit ADC sampling a half-rail input.

Capability validation

Asking for a resolution the SoC doesn't support fails at _open():

alp_adc_open(&(alp_adc_config_t){ .resolution_bits = 16 });
// adc == NULL, alp_last_error() == ALP_ERR_OUT_OF_RANGE

See also

• <alp/adc.h> reference
• <alp/dsp.h> — FIR / IIR / FFT chains for streaming
• Examples overview