Configuring ADC for multichannel using nrfx driver in nrf connect sdk

[ShahzaibShamim]

Hello. I am facing an issue in configuring ADC for multichannels. I was looking at the Nordic fundamentals course Lesson 6 Exercise 2.In this example, the adc is configured to scan single channel when I changed some settings to scan 4 channels I got this error and my code is not working.

I don't know what am I doing wrong. I want adc to scan in interrupt. Here is my code.

#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>
#include <nrfx_saadc.h>
#include <stdint.h>

/* STEP 3.1 - Declare the struct to hold the configuration for the SAADC channel used to sample the battery voltage */
static nrfx_saadc_channel_t channel[4] = {
	NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN0, 0),
	NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN1, 1),
	NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN2, 2),
	NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN3, 3)
};

/* STEP 3.2 - Declare the buffer to hold the SAAD sample value */
static int16_t sample[4];
static uint32_t counter = 0;

/* STEP 4.1 - Define the battery sample interval */
#define BATTERY_SAMPLE_INTERVAL_MS 1000

/* STEP 4.3 - Add forward declaration of timer callback handler */
static void battery_sample_timer_handler(struct k_timer *timer);

/* STEP 4.2 - Define the battery sample timer instance */
K_TIMER_DEFINE(battery_sample_timer, battery_sample_timer_handler, NULL);

/* STEP 7.1 - Implement timer callback handler function */
void battery_sample_timer_handler(struct k_timer *timer)
{
	/* STEP 7.2 - Trigger the sampling */
	nrfx_err_t err = nrfx_saadc_mode_trigger();
	if (err != NRFX_SUCCESS)
	{
		printk("nrfx_saadc_mode_trigger error: %08x", err);
		return;
	}

	printk("\n-------------------Reading - %d-------------------\n", counter++);
	for (int i = 0; i < 4; i++)
	{
		printk("SAADC%d sample: %d    \n", i, sample[i]);
	}
}

static void configure_saadc(void)
{
	/* STEP 5.1 - Connect ADC interrupt to nrfx interrupt handler */
	IRQ_CONNECT(DT_IRQN(DT_NODELABEL(adc)), DT_IRQ(DT_NODELABEL(adc), priority), nrfx_isr, nrfx_saadc_irq_handler, 0);

	/* STEP 5.2 - Connect ADC interrupt to nrfx interrupt handler */
	nrfx_err_t err = nrfx_saadc_init(DT_IRQ(DT_NODELABEL(adc), priority));
	if (err != NRFX_SUCCESS)
	{
		printk("nrfx_saadc_mode_trigger error: %08x", err);
		return;
	}

	/* STEP 5.3 - Configure the SAADC channel */
	for (int i = 0; i < 4; i++)
	{
		channel[i].channel_config.gain = NRF_SAADC_GAIN1_4;
		channel[i].channel_config.acq_time = NRF_SAADC_ACQTIME_40US;
		channel[i].channel_config.reference = NRF_SAADC_REFERENCE_VDD4;

		err = nrfx_saadc_channels_config(&channel[i], (i + 1));
		if (err != NRFX_SUCCESS)
		{
			printk("nrfx_saadc_channels_config error: %08x", err);
			return;
		}
	}

	/* STEP 5.4 - Configure nrfx_SAADC driver in simple and blocking mode */
	err = nrfx_saadc_simple_mode_set(BIT(0) | BIT(1) | BIT(2) | BIT(3),
									 NRF_SAADC_RESOLUTION_12BIT,
									 NRF_SAADC_OVERSAMPLE_DISABLED,
									 NULL);
	if (err != NRFX_SUCCESS)
	{
		printk("nrfx_saadc_simple_mode_set error: %08x", err);
		return;
	}

	/* STEP 5.5 - Set buffer where sample will be stored */
	err = nrfx_saadc_buffer_set(&sample, 4);
	if (err != NRFX_SUCCESS)
	{
		printk("nrfx_saadc_buffer_set error: %08x", err);
		return;
	}

	/* STEP 6 - Start periodic timer for battery sampling */
	k_timer_start(&battery_sample_timer, K_NO_WAIT, K_MSEC(BATTERY_SAMPLE_INTERVAL_MS));
}

int main(void)
{
	configure_saadc();

	k_sleep(K_FOREVER);
	return 0;
}

[Vidar Berg]

Hello,

The function nrfx_saadc_channels_config() returns NRFX_ERROR_INVALID_PARAM according to your crash log. This might be happening because you're increasing the channel_count with every iteration. Please try setting it to 1 instead.

Best regards,

Vidar

[ShahzaibShamim]

I changed it to 1 but still not working, now crash code is 0bad0006

[Vidar Berg]

0x0bad0006 is NRFX_ERROR_INVALID_LENGTH. Which function was this error returned from?

[ShahzaibShamim]

From configure_saadc()

[Vidar Berg]

You need to check which nrfx_* function it was returned from.

[ShahzaibShamim]

nrfx_saadc_simple_mode_set(BIT(0) | BIT(1) | BIT(2) | BIT(3),

                                     NRF_SAADC_RESOLUTION_12BIT,

                                     NRF_SAADC_OVERSAMPLE_DISABLED,

                                     NULL);

this function, when I removed BIT(1) | BIT(2) | BIT(3)

it is working or when I set it to only one bit like BIT(2) it is also working but with bit masking, it is not working.

[Vidar Berg]

Please post the debug log.

[ShahzaibShamim]

I somehow fixed the code and it is working fine. Scans 4 channels in interrupt. Here is the code

#include <zephyr/kernel.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/sys/printk.h>

/* STEP 2 - Include header for nrfx SAADC driver */
#include <nrfx_saadc.h>

#define SAADC_CHANNEL_COUNT     4
#define GreenLED1_NODE          DT_ALIAS(greenled1)

static const struct gpio_dt_spec led1 = GPIO_DT_SPEC_GET(GreenLED1_NODE, gpios);

/* STEP 3.1 - Declare the struct to hold the configuration for the SAADC channel used to sample the battery voltage */
static nrfx_saadc_channel_t channels[SAADC_CHANNEL_COUNT] = {
    NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN0, 0),
    NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN1, 1),
    NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN2, 2),
    NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN3, 3),
};

/* STEP 3.2 - Declare the buffer to hold the SAAD sample value */
static int16_t sample[SAADC_CHANNEL_COUNT];

/* STEP 4.1 - Define the battery sample interval */
#define BATTERY_SAMPLE_INTERVAL_MS 50

/* STEP 4.3 - Add forward declaration of timer callback handler */
static void battery_sample_timer_handler(struct k_timer *timer);

/* STEP 4.2 - Define the battery sample timer instance */
K_TIMER_DEFINE(battery_sample_timer, battery_sample_timer_handler, NULL);

static void saadc_event_handler(nrfx_saadc_evt_t const *p_event)
{
    if (p_event->type == NRFX_SAADC_EVT_DONE)
    {
        nrfx_err_t err;

        // Retrieve the sampled data from the buffer
        for (int i = 0; i < p_event->data.done.size; i++)
        {
            sample[i] = p_event->data.done.p_buffer[i];
        }

        // Print voltage values
        float voltage[4] = {0.0f};
        for (int i = 0; i < SAADC_CHANNEL_COUNT; i++)
        {
            sample[i] = MAX(sample[i], 0);
            voltage[i] = (sample[i] / 4096.0f * 3.3f);
            printk("Channel %d sample: %d    %.3f\n", i, sample[i], voltage[i]);
        }

        printk("\n\n");

        // Re-set the buffer and start another sampling cycle
        err = nrfx_saadc_buffer_set(p_event->data.done.p_buffer, SAADC_CHANNEL_COUNT);
        if (err != NRFX_SUCCESS)
        {
            printk("nrfx_saadc_buffer_set error: %08x", err);
        }
    }
}

/* STEP 7.1 - Implement timer callback handler function */
void battery_sample_timer_handler(struct k_timer *timer)
{
    /* STEP 7.2 - Trigger the sampling */
    nrfx_err_t err = nrfx_saadc_mode_trigger();
    if (err != NRFX_SUCCESS)
    {
        printk("nrfx_saadc_mode_trigger error: %08x", err);
        return;
    }

    /* STEP 7.3 - Calculate and print voltage */
    // int battery_voltage = ((600 * 6) * sample) / ((1 << 12));

    float voltage[4] = { 0.0f };

    for (int i = 0; i < SAADC_CHANNEL_COUNT; i++)
    {
        voltage[i] = (sample[i] / 4096.0f * 3.3f);
        printk("Channel %d sample: %d    %.3f\n", i, sample[i], voltage[i]);
    }

    printk("\n\n");
    // printk("Battery Voltage: %d mV\n", battery_voltage);
}

static void configure_saadc(void)
{
    /* STEP 5.1 - Connect ADC interrupt to nrfx interrupt handler */
    IRQ_CONNECT(DT_IRQN(DT_NODELABEL(adc)),
                DT_IRQ(DT_NODELABEL(adc), priority),
                nrfx_isr, nrfx_saadc_irq_handler, 0);

    /* STEP 5.2 - Connect ADC interrupt to nrfx interrupt handler */
    nrfx_err_t err = nrfx_saadc_init(DT_IRQ(DT_NODELABEL(adc), priority));
    if (err != NRFX_SUCCESS)
    {
        printk("nrfx_saadc_mode_trigger error: %08x", err);
        return;
    }

    /* STEP 5.3 - Configure the SAADC channel */
    for (int i = 0; i < SAADC_CHANNEL_COUNT; i++)
    {
        channels[i].channel_config.gain = NRF_SAADC_GAIN1_4;
        channels[i].channel_config.reference = NRF_SAADC_REFERENCE_VDD4;
        channels[i].channel_config.acq_time = NRF_SAADC_ACQTIME_40US;
    }
    err = nrfx_saadc_channels_config(&channels[0], 4);
    if (err != NRFX_SUCCESS)
    {
        printk("nrfx_saadc_channel_init error for channel %08x\n", err);
        return;
    }

    /* STEP 5.4 - Configure nrfx_SAADC driver in simple and blocking mode */
    err = nrfx_saadc_simple_mode_set(BIT(0) | BIT(1) | BIT(2) | BIT(3),
                                     NRF_SAADC_RESOLUTION_12BIT,
                                     NRF_SAADC_OVERSAMPLE_DISABLED,
                                     saadc_event_handler);
    if (err != NRFX_SUCCESS)
    {
        printk("nrfx_saadc_simple_mode_set error: %08x", err);
        return;
    }

    /* STEP 5.5 - Set buffer where sample will be stored */
    err = nrfx_saadc_buffer_set(&sample, 4);
    if (err != NRFX_SUCCESS)
    {
        printk("nrfx_saadc_buffer_set error: %08x", err);
        return;
    }

    /* STEP 6 - Start periodic timer for battery sampling */
    k_timer_start(&battery_sample_timer, K_NO_WAIT, K_MSEC(BATTERY_SAMPLE_INTERVAL_MS));
}

int configureLED(void)
{
    int ret;

    if (!device_is_ready(led1.port))
    {
        printk("Device %s is not ready\n", &led1.port->name);
        return -1;
    }
    ret = gpio_pin_configure_dt(&led1, GPIO_OUTPUT_INACTIVE);
    if (ret)
    {
        printk("%s failed init (err %d)\n", "LED1", ret);
        return -1;
    } 
}

int main(void)
{
    int ret;

    printk("ADC Multichannel scan\n");
    configureLED();
    configure_saadc();

    while(1)
    {
        ret = gpio_pin_toggle_dt(&led1);
        if (ret < 0)
        {
            return 0;
        }
        k_msleep(100);
    }

    return 0;
}

Thanks for your help.