Recently I came across an interesting little ARM Cortex M0 microcontroller nrf51822, which has an integrated low energy Bluetooth (BLE) and overall is a very capable to do other tasks besides BLE especially due to its immense FLASH memory and RAM which is 256kb and 32kb accordingly (varies between models). Immediately I thought of trying to make a simple smart-watch for various reasons like low energy mode, which I think was 0.1µA in sleep mode. Only drawback compared to other ARM Cortex series microcontrollers is that it’s not really the fastest in the market, however a new one will be coming soon by first quarter of 2016, which will be more efficient, faster and overall more capable SOC. Luckily for us, their SDKs are pretty much identical, and once you learn and understand how nrf51 series SDK is structured and how to use it then switching to nrf52 shouldn’t be a problem. In any case I bought the development board BLE400 which is pictured above to play around; nonetheless I highly recommend buying the original nrf51-DK board just to support Nordic for developing an awesome micro.