RE: BLE battery update

Karl Ylvisaker — Wed, 29 Sep 2021 07:40:29 GMT

Hello,

I suspect that there is just a logical error with your formula for converting the SAADC's digital output to voltage.

Could you show me what your log looks like when you see this behavior?
How did you verify that the battery's remaining charge was actually 54%?
The formula from the SAADC documentation for converting from digital output to analogue value uses millivolts - it seems your are multiplying it by 1000 an additional time, before passing it to the battery_level_percent function that seems to use millivolts as well.
Furthermore, which battery are you using, and have you taken the battery_level_percent function from the SAADC's example (which is made specifically for CR2032 coin cell batteries), or did you create this yourself for the discharge curve of the specific battery you are using?

Additionally, to increase stability and/or accuracy of the battery measurement you could use oversampling to reduce the impact of noise.
You can also have the SAADC measure directly on the VDD bus by providing NRF_SAADC_INPUT_VDD to the channel configuration macro.

Looking forward to resolving this issue together!

Best regards,
Karl