nrf52 Battery Measurements

[Bilal]

How can i sample nrf52 own input voltage to do battery measurements?My nrf52 chip is directly connected to a battery and it needs to sample its own input voltage without a voltage divider. In the end my goal is to get battery measurement on my board.

It would be really helpful if you guide me or point me to the documentation where I can find help.

Thank You

[Kenneth]

That should simply be opening \examples\peripheral\saadc from a recent nRF5 SDK and change to in saadc_init():

nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);

[Bilal]

Hello Kenneth,

Does it only depends on input voltage ? because most of the example I see has voltage dividers as well. In my setup, chip is directly connected to battery. Thanks

[Kenneth]

I assume the battery is below 3.6V at all times. In that case you don't need a resistor bridge. Internally there is already a 1/6 divider and a 0.6V reference. So this means  that if you measure 3V battery, the measurement will be 3V/6 = 0.5V. If you have 8bit resolution, then you will measure approx 2^8 * (0.5V/0.6V) = 213 decimal @ 8bit resolution (or 2^10 * (0.5V/0.6V) = 853 decimal @ 10bit) when VDD= 3V.