Compiling for a wristband (ID115)

Basically you need BOARD=NRF51822DK RELEASE=1 make (not NRF51822DK=1), then you should be ok.

That worked! Thanks. This evening I'll try to drive the OLED display thanks to the documentation provided by [rbaron] : https://rbaron.net/blog/2018/05/27/Hacking-a-cheap-fitness-tracker-bracelet.html