Advertising Battery levels on a beacon

[Chris Butler]

Hey folks,

I am currently trying to use my nrf51822 evaluation board as a beacon. This is working pretty well but I need to have it broadcast its current battery level as well. From what I have seen this means I need to make some kind of interrupt to tell the chip to update the advertising message. Could anyone point me in the direction of some information on this topic?

If it helps I am currently basing everything off of the ble_app_beacon example code and that works just fine.

-Chris

[Ole Morten]

This is actually implemented in the nrf51-ble-app-temp, available here, so I'd recommend you to take a look on it. In summary, it uses app_timer to trigger a periodic timeout, in which it uses the ADC to measure the battery level, and updates the advertisement data.

[Chris Butler]

Those links help a good bit. I am still struggling with how exactly the calculation works and how I can verify it. Testing my actual battery voltage gives me 3.0v outside of the circuit, testing it in the working circuit gives 2.85v, the ACD however gives 0x55( or 85%) out of 3.0v which would correspond to 2.55v. When using the devlopement board with USB power it reads 0x65 when the max voltage is set to 3.0v in the code. What would be causing this discrepancy?