nRF54L15 ADC channels not reading correctly

[Jishnu K J]

Hi,

I’m working with nRF54L15 (nRF54L15 DK) using NCS v3.0.2, and I’m facing an issue with ADC channel readings.

I configured the following ADC channels:

• AIN3 → P1.07

• AIN6 → P1.13

• AIN7 → P1.14

Devicetree overlay

/ {
    zephyr,user {
        io-channels = <&adc NRF_SAADC_AIN3>,  /* P1.07 */
                      <&adc NRF_SAADC_AIN6>,  /* P1.13 */
                      <&adc NRF_SAADC_AIN7>;  /* P1.14 */
    };
};

ADC configuration

#define ADC_NODE DT_NODELABEL(adc)

static const struct device *adc_dev = DEVICE_DT_GET(ADC_NODE);

void adc_init(void)
{
    if (!device_is_ready(adc_dev)) {
        printk("ADC device not ready\n");
        return;
    }

    struct adc_channel_cfg ch_cfg = {
        .gain = ADC_GAIN_1,
        .reference = ADC_REF_EXTERNAL0,
        .acquisition_time = ADC_ACQ_TIME_DEFAULT,
        .differential = 0,
    };

    uint8_t ain_map[3] = {3, 6, 7};  // AIN3, AIN6, AIN7

    for (int i = 0; i < 3; i++) {
        ch_cfg.channel_id = i;
        ch_cfg.input_positive = ain_map[i];

        int ret = adc_channel_setup(adc_dev, &ch_cfg);
        if (ret) {
            printk("Channel %d setup failed: %d\n", i, ret);
            return;
        }
    }
}

ADC read

void Read_adc_values(void)
{
    int16_t raw_buf[3];

    struct adc_sequence sequence = {
        .channels = BIT(0) | BIT(1) | BIT(2),
        .buffer = raw_buf,
        .buffer_size = sizeof(raw_buf),
        .resolution = 12,
    };

    int ret = adc_read(adc_dev, &sequence);
    if (ret) {
        printk("ADC read failed: %d\n", ret);
        return;
    }

    printk("CH0 (AIN3 / P1.07): %d\n", raw_buf[0]);
    printk("CH1 (AIN6 / P1.13): %d\n", raw_buf[1]);
    printk("CH2 (AIN7 / P1.14): %d\n", raw_buf[2]);
}

---

Observed behavior

When connecting the sensor:

• On P1.13 (expected AIN6) → only AIN7 channel shows valid readings

• AIN3 and AIN6 always return ~4092 (full-scale)

Example output:

CH0 (AIN3 / P1.07): 4092
CH1 (AIN6 / P1.13): 4092
CH2 (AIN7 / P1.14): 2532

Additionally:

• Connecting the sensor to P1.07 or P1.14 does not change readings

• Only P1.13 seems to affect ADC output, but it appears on AIN7

Questions

1. What is the correct AIN - GPIO mapping for nRF54L15 DK?
2. Are P1.07 and P1.14 valid ADC input pins?
3. Is any additional configuration required for ADC inputs on nRF54?

---

Any guidance on correct ADC channel  pin mapping for nRF54L15 would be very helpful.

Thanks!

[Kazi Afroza Sultana]

Hello Jishnu,

I am very glad to hear that. :) 

Thanks.

BR
Kazi