LimiFrog is a Bluetooth 4.1 Wearables Devkit Based on STM32L4 with Lots of Sensors (Crowdfunding)

LimitFrog is a tiny board powered by STMicro STM32-L4 microcontroller with Bluetooth 4.1 connectivity, plenty of sensors, and that can run code bare metal as well as RiOT real-time operating system.

LimifrogLimiFrog specifications:

  • MCU – STMicro STM32-L4 ARM Cortex M4 micro-controller @ 80 MHz with DSP, 512KB flash, 128KB RAM
  • External storage – 8MB serial flash for data that supports FAT32 file system
  • Display – 160×128 RGB565 OLED display
  • Connectivity – Bluetooth 4.1 (Panasonic PAN1740)
  • Sensors (Follow this link for datasheets of most components)
    • Pressure, altitude & temperature (LPS25H)
    • 3-axis accelerometer, 3-axis gyroscope (LSM6DS3)
    • 3-axis magnetometer (LIS3MDL)
    • Ambient light, proximity and distance (VL6180X)
    • Ambient sound (SPU0414H5H)
  • USB – micro USB port for power and programming
  • Expansions – 11-pin (through holes) providing access to SPI, I2C, CAN, PWM, GPIOs, ADC, DAC, Analog out, and power signals (3V out GND)
  • Battery – 500 mAh (hours to weeks of battery life depending on application)
  • Dimensions – N/A (but small)

Limifrog_block_diagramThe “basic” version does not come with sensors, Bluetooth 4.1, nor OLED display, so these are optional, and three more versions are offered “Sense”, “Sense’m comm” and “Full Monty” if you want more features.

LimiFrog can currently be programmed in C/C++, and MicroPython support is in the works. The libraries include a USB stack, a FAT file system, and graphics support. As mentioned in the introduction, programs can run bare metal, or using RiOT real-time operating system.

Software Architecture
Software Architecture

The company also provided a code sample in C if you want to check what the API looks like.

The project has launched on Kickstarter, and rewards start at 39 Euros for the “basic” version of the board with a LiPo battery, software packages, 3D printer files for the case, and up to 99 Euros for the “full monty” including Bluetooth 4.1, the OLED display, and all sensors. Delivery is scheduled for January 2016, and shipping costs between 8 and 12 Euros depending on the chosen rewards. More information may also be found on

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3 Replies to “LimiFrog is a Bluetooth 4.1 Wearables Devkit Based on STM32L4 with Lots of Sensors (Crowdfunding)”

  1. Interesting, seems like a development of the old STM32F4-DISCOVERY board. The kickstarter doesn’t say what sensors (if any) the BASIC model has, i think it would be a bit useless without any of the sensors really.

  2. So for the price of a smartphone (99 Euro) you get a wearable sensor set, but with less RAM and CPU than a smartphone?
    Hmmm … does not sound very interesting to me. I would be interested in such a wearable for 25 Euro. And a basic wearable for 12 Euro.

  3. Hi Brian,
    It’s a new dev, not derived from F4-DISCOVERY. The idea is to come up with something much more compact than classical dev boards, while pre-integrating more features.
    The “basic” version does not have the sensors – it’s a minimal version which, compared to a standard MCU dev board, brings: lightness (20g or so) and compactess, some integrated data storage (64Mbit, usable as file system) and integrated USB-rechargeable LiPo battery — will also run MicroPython if you like it. But I agree it’s probably not the most interesting version for many people, who may want to check the next versions up (sensors/BLE/OLED).

    Hi Sander,
    It’s not same usage as a smartphone. You won’t program your smartphone in C, you won’t have e.g. direct access to sensors registers, you probably won’t use it to show a proof of concept of your wearable product.
    Would love pricing to be as aggressive as that of a low-cost smarptphone produced in tens of millions units or more, but we’re not quite there yet. Anyway I suppose you can’t expect a dev board to match the price of a consumer product. People who can already run boards in massive quantities don’t need backers on kickstarter to get their project started, either.

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