I have developed an ESP8266 solution for small-scale IoT prototyping based around the ESP12x form factor in the ESP8266 series of IoT microcontrollers. In my experiments and research in the IoT space the need for compact, battery-powered prototyping platforms was sometimes necessary.

Many others like me have encountered the same frustration trying to rig multiple different power modules, just to get a LiPo charging circuit connected to a microcontroller while still maintaining USB connectivity. The first sacrifice is often size – by the time you put together the buck/boost regulator, the charging circuitry and the microcontroller itself, you would have in your hands an unwieldy hodge-podge of soldered daughterboards that you will most likely find too big for your miniaturisation efforts.

This solution of mine was developed to address those issues. Yes, it’s based on the older ESP8266 chip, but it is still a decent little microcontroller compared to its newer sibling, the ESP32. The key here is size – the ESP-12F (and other 12x series) designs are widely available and the small footprint is very hard to beat for its price.

I have elected to continue using a 2mm pitch for the board, to keep it compact. The ESP-12F board, with its castellated edges, goes onto a 2mm pitch mainboard containing an on-board JST 2mm battery connector, power recharging and buck/boost circuitry.

Early production shot of mainboard and programmer

Programming the ESP-12F is done using a programmer board, itself relying on an FTDI-232L USB cable to connect to the computer. The large programmer board is excluded from the main board to keep costs low, and also maintain the small size of the ESP-12F. All assembled the board is exactly the same size as a Particle Photon, making use of both sides of the board to hold the charging and buck/boost circuitry.

At the same time, the programmer board’s breakout pins, large switches for debugging/uploading, and a slot to allow the ESP-12F board’s JST battery plug to remain connected to the board makes USB programming and debugging easy.

More work is still needed to get it to a point where it’s ready for prime time, and hopefully, for sale. As the design iterations and prototyping reaches a certain level of maturity, I’ll be releasing more details and provide tutorials on how to use it.