Dev Academy Lesson 6 Exercise 2 – nrfx ADC is non-blocking but does not wait for conversion to complete

[chris22222]

Working through the dev academy exercise, it appears that the sample code does not wait for the conversion to complete before reading out the sample:

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/* 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));

· · · · printk("SAADC sample: %d\n", sample);

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

}

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/* 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));

        printk("SAADC sample: %d\n", sample);
        printk("Battery Voltage: %d mV\n", battery_voltage);

}

https://github.com/NordicDeveloperAcademy/ncs-inter/blob/main/v2.6.2-v2.5.2/l6/l6_e2_sol/src/main.c

Would it not be more appropriate to get a call back from the nrfx_saadc_irq_handler when the conversion is complete?

When using the Zephyr ADC driver on the same exact board, it appears the ADC measurements are ~30 mV different.

Can you please confirm if we should be waiting for the conversion to complete here?