Developed by Xavier Cauchy, an engineer with a strong background in circuit and SoC design acquired while at STMicroelectronics, LimiFrog is a programmable, ultra-compact electronic module (44x41 mm or 1.7''x1.6'', for a weight of 25g) ...intended for prototyping connected objects of small size, notably wearable electronics devices. One innovation of this open-source board, apart from its dimensions, is to combine a powerful computation and processing architecture – a 32-bit, ARM Cortex-M4 based STM32-L4 from STMicroelectronics, complemented with an 8MByte Flash memory – with a BlueTooth 4.1 interface (with integrated antenna) and a 160x128 pixelcolor display in Oled technology (36x31mm or 1.4''x1.2''). In addition, a wide range of sensors are integrated on board: 3-axis accelerometer, 3-axis gyroscope, 3-axis magnetometer, atmospheric pressure and temperature sensor, microphone, ambient light sensor and proximity detector.

The use of an STM32-L4 ensures an extremely low current consumption, of the order of 100uA/MHz in active mode and down to 30nA in shut-down (or sleep) mode. Power is provided by a 500mA.h lithium-polymer (LiPo) battery, rechargeable through the integrated USB2.0 port.

On the programming side, Xavier Cauchy has chosen to ease accessibility for beginners while allowing seasoned developers to make the most of the potential of this 32-bit micro-controller. This is achieved via an out of the box, ready to run configuration file for  the board (avoiding complex I/O or interrupt configurations, etc.), a ready-to-use middleware (USB driver, FAT File System...) and an API. Depending on end user preference, it is possible to develop in C or C++ and, in the near future, in MicroPython – an implementation of the Python 3.4 language optimised for micro-controllers. It is worth noting that LimiFrog may also be used for complex projects with embedded real-time OS, and a porting of the RIOT open-source system dedicated to the Internet of Things is on-going.

To finalize this project and make it a reality, a crowd-funding campaign on web site Kickstarter has just been launched by its developer (the complete description of the project is here). Objective: ensure a pre-industrialization of this prototyping board, more powerful and more integrated than an Arduino platform, by early 2016.