I created a separate Hackaday project for an adapter board for nRF51822 Core Bluetooth Low Energy modules that I intend to use in both the PiChart display device and the wireless GPS & compass module.

The nRF51822 is a really nice, inexpensive (from €3.5 each for the ICs in single unit volume) very low energy chip which is both an ARM micro controller and a Bluetooth Low Energy (BLE) device.

You can buy cheap modules with the nRF51822 for under €5 on E-bay, known as nRF51822-Core. But they use 2 mm pitch connectors which are a pain, since they don't fit into breadboards.

There is a "motherboard" for these modules available, called BLE400. But it didn't fit my needs (I don't need the USB-serial chip on it, I can't choose what voltage to run it at, it doesn't have voltage shifters neccessary to work with the GPS and compass boards I bought, and it's pretty big (ca 10 x 5 cm).

So I decided to design my own adapter board that I could re-use in different projects, with footprints where I could mount additional components as I need them - LDO, voltage shifters, programming connector, reset button, LEDs, MOSFETS to turn off power to peripherals, and pads for headers so that I can connect it to a breadboard or a Raspberry Pi.