SDK 1.6.1 Zephyr, How Read nRF52832 AIN7 and configure prj.conf and overlay file.

[Fb62]

Hello, how do I configure the prj.conf file and the overlay file and how do I read the AIN7 analog input (P0.31) of the nRF52832. It is the first time that I use the micro to read an analog voltage. I did various research on DevZone, but I couldn't figure out how to do it. Thanks in advance.

[Heidi]

Hi!

You can add the following code snippet to convert the raw ADC reading to millivolts. 

mV = (int16_t)adc_raw;
err = adc_raw_to_millivolts(adc_ref_internal(dev_adc), channel_cfg.gain,
			   sequence.resolution, &mV);
if (err) {
	printk("ADC conversion failed: %d\n", err);
	return;
}
printf("ADC raw %d => %d mV\n", (int16_t)adc_raw, mV);					   

I attached a zip file of the application below.

adc_sample.7z

[Fb62]

Hi,

I compiled the last adc_sample code, but I get

*** Booting Zephyr OS build v2.6.0-rc1-ncs1 ***
ADC raw 4095 => 599 mV
ADC raw 4095 => 599 mV
ADC raw 4095 => 599 mV
ADC raw 4095 => 599 mV
ADC raw 4095 => 599 mV
ADC raw 4095 => 599 mV

In input of AN7 I have 1.7 Volt but the ADC reaches full scale with only 0.6 volts

Is there any other settings to be made?
My hardware is the pine watch which has a resistive divider which halves the battery voltage which is about 3.7Volt

Best Regards

Fausto

[Heidi]

Hi!

Try setting the gain to ADC_GAIN_1_6 to get a range of 0V - 3.6V.

[Fb62]

Hi,

OK, work now.

Best Regards

Fausto