Measure the voltage with adc pin?

[Taner]

I would like to close a button cell battery (3V) directly to VDD and define the VDD as ADC input. I would like to measure the button cell battery voltage via the internal reference voltage. I do not want to show anything, but an LED should light up when the battery voltage is only 2.5V. Will this work without external components. Can the software realize this?

Thanks!

[Jørgen Holmefjord]

Hi,

Yes, this can all be handled in software. Start with the SAADC peripheral example in the SDK, set the input to NRF_SAADC_INPUT_VDD. In the saadc_callback, calculate the voltage from the measured sample, and if it is equal to the voltage you want, set the GPIO to the LED using the GPIO HAL functions.

Best regards,
Jørgen

[Taner]

Thanks for your answer!

Since I want to use a pre-certified module, I only have one VDD input. Could this cause problems?

[Jørgen Holmefjord]

Setting the input to NRF_SAADC_INPUT_VDD will internally connect the analog input to VDD. You do not have to physically connect it.

[Taner]

Thanks!