Battery Sample - runtime error "voltage: setup: -134"

[cbraissant]

Hello, 

I'm building the sample Measure battery voltage on a custom board, and I have an error voltage: setup: -134  at runtime.

SEGGER J-Link V7.94i - Real time terminal output
SEGGER J-Link (unknown) V1.0, SN=1050264300
Process: JLink.exe
[00:00:00.390,777] <err> voltage: setup: -134
*** Booting nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
[00:00:04.254,882] <inf> BATTERY: Setup AIN2 got 0
[00:00:04.254,882] <inf> BATTERY: Battery setup: 0 1
[00:00:04.262,878] <inf> BATTERY: raw 1348 ~ 296 mV => 3256 mV

The overlay file is configure as explained in the sample:

/{
        vbatt {
                compatible = "voltage-divider";
                io-channels = <&adc 2>;
                output-ohms = <100000>; // 100k
                full-ohms = <(100000 + 1000000)>; // 100k + 1M
                power-gpios = <&gpio0 11 GPIO_ACTIVE_HIGH>;
        };
};

&adc {
        status = "okay";
};

And the code in the sample has not been changed.

I use the SDK v2.9.0

---

From what I can trace, the compatible = "voltage-divider"; will configure the .config with DT_HAS_VOLTAGE_DIVIDER_ENABLED, therefore enabling the "voltage_divider" folder located in <zephyr/drivers/sensors/voltage_divider>.

The error comes from the file voltage.c, more specifically the initialisation function called by the macro DT_INST_FOREACH_STATUS_OKAY(VOLTAGE_INIT)

static int voltage_init(const struct device *dev)
{
	const struct voltage_config *config = dev->config;
	struct voltage_data *data = dev->data;
	int ret;

	if (!adc_is_ready_dt(&config->voltage.port)) {
		LOG_ERR("ADC is not ready");
		return -ENODEV;
	}

	if (config->gpio_power.port != NULL) {
		if (!gpio_is_ready_dt(&config->gpio_power)) {
			LOG_ERR("Power GPIO is not ready");
			return -ENODEV;
		}
	}

	ret = adc_channel_setup_dt(&config->voltage.port);
	if (ret != 0) {
		LOG_ERR("setup: %d", ret);
		return ret;
	}

	ret = adc_sequence_init_dt(&config->voltage.port, &data->sequence);
	if (ret != 0) {
		LOG_ERR("sequence init: %d", ret);
		return ret;
	}

	data->sequence.buffer = &data->raw;
	data->sequence.buffer_size = sizeof(data->raw);

	return pm_device_driver_init(dev, pm_action);
}

#define VOLTAGE_INIT(inst)                                                                         \
	static struct voltage_data voltage_##inst##_data;                                          \
                                                                                                   \
	static const struct voltage_config voltage_##inst##_config = {                             \
		.voltage = VOLTAGE_DIVIDER_DT_SPEC_GET(DT_DRV_INST(inst)),                         \
		.gpio_power = GPIO_DT_SPEC_INST_GET_OR(inst, power_gpios, {0}),                    \
	};                                                                                         \
                                                                                                   \
	PM_DEVICE_DT_INST_DEFINE(inst, pm_action);                                                 \
                                                                                                   \
	SENSOR_DEVICE_DT_INST_DEFINE(inst, &voltage_init, PM_DEVICE_DT_INST_GET(inst),             \
			      &voltage_##inst##_data, &voltage_##inst##_config, POST_KERNEL,       \
			      CONFIG_SENSOR_INIT_PRIORITY, &voltage_api);

DT_INST_FOREACH_STATUS_OKAY(VOLTAGE_INIT)

The function adc_channel_setup_dt(&config->voltage.port) will fail as it is called POST_KERNEL and the parameters of the ADC are not configured yet.

The driver for adc is <zephyr/drivers/adc/adc_nrfx_saadc> and the function:

/* Implementation of the ADC driver API function: adc_channel_setup. */
static int adc_nrfx_channel_setup(const struct device *dev,
				  const struct adc_channel_cfg *channel_cfg)
{
...
}

implement the adc_channel_setup.

I'm not sure where the error is coming from next, but I guess from

int ret = adc_convert_acq_time(channel_cfg->acquisition_time, &config.acq_time);

as the acquisition time of the ADC has never been defined, and is done at run time in the sample (therefore at APPLICATION level and not POST_KERNEL).

Could you tell me why the ADC is not configured in the overlay file for something similar as:

&adc {
        #address-cells = <1>;
        #size-cells = <0>;
        status = "okay";
        channel@0 {
                reg = <0>;
                zephyr,gain = "ADC_GAIN_1_6";
                zephyr,reference = "ADC_REF_INTERNAL";
                zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
                zephyr,input-positive = <NRF_SAADC_AIN2>;
                zephyr,resolution = <12>;
        };
};

I checked as well the board definiton for the Nordic Thingy52 and there is not definition for the ADC, therefore I guess the error is happening as well.

Please, let me know how to get rid of that error, and correct the sample if necessay. 

Thank you.