Awesome

HMSensor

Flexible and tiny (40x20mm) Hardware Platform for 868MHz Sensors and Actors.

It comes in tow different variants:

• StepUp: For Batter or PowerSupply usage
• CR2032: For even smaller coin battery applications

Extensible with AddOn-Boards.

• Some (german) documentation is available at https://asksinpp.de/Projekte/psi/HMSensor
• Helper PCB for flashing: https://github.com/psi-4ward/HMSensor-FlashStation