ADC calculation formula

[sharmelaraju]

Hi,

We are using NRF52840 in our project. Here my doubt is  we  need to read the voltage from the sensor which will vary from 0 to 5 v   .Can you plz tell me which example program i need to use  for reading the  voltage as i didnt get the ADC example program in the SDK 15.3 . And also plz tell me what are the ADC pin in the NRF52840 as i am not getting. And also plz tell me the  ADC calculation formula, ,resolution, Reference voltage. Plz give me the solution for this.

[pdpro]

Are you still at design phase or already designed the board? Go through datasheet & product specifications, you'll find 8 pins (AIN0-AIN7) corresponding to analog input. For example, p0.02 GPIO can be used as AIN0 as shown here:

Further, you need to use SAADC example present in SDK for getting values from analog pins. All ADC related specs are available in product spec or SAADC example has all related configuration.

[sharmelaraju]

Thanks for the reply.

Still we are in design phase and also i am new to this controller.

I will try and let you know if i have some doubt.

[sharmelaraju]

 I am getting the adc value.So, i need to convert into voltage value.

Can you plz give me the ADC calculation formula so that i can convert into voltage.

[Susheel Nuguru]

in SDK16.0\examples\ble_peripheral\ble_app_proximity\main.c the raw conversion macro is shown as

#define ADC_RESULT_IN_MILLI_VOLTS(ADC_VALUE)\
        ((((ADC_VALUE) * ADC_REF_VOLTAGE_IN_MILLIVOLTS) / ADC_RES_10BIT) * ADC_PRE_SCALING_COMPENSATION)

you need to probably offset the value with some voltage drops caused by any passive components you have that affects the ADC measurement.

[sharmelaraju]

Thanks for the reply .

I will check