The Nerdonic Exen Mini Board

Alasdair Allan
3 min readJul 5, 2018

One thing you see a lot when you write about maker electronics are microcontroller boards being announced as the “smallest,” or “fastest.” Regretfully you rarely see anyone announcing the “cheapest,” although there have been rare exceptions to that rule.

So given that everyone else claims it as well, I’m somewhat dubious when told that the Nerdonic Exen Mini is the “…smallest 32-bit dev board.” Because I’m sure I’ve come across smaller, yet I can’t lay my hands on one right away. Because despite my doubts, you have to admit, it is a really small board.

The Nerdonic Exen Mini. (📷: Nerdonic)

Measuring 14.9×14.9×4.4 mm, which is 0.587×0.587×0.17 inches, and weighing in at 0.95 grams, or 0.034 ounces, the Exen Mini is built around an Arm Cortex-M0+ running at 48MHz clock with 256KB of flash memory and 32KB of SRAM onboard.

The Exen Mini next to a British 5p piece, which is about the size of a US dime. (📷: Nerdonic)

The board is fully compatible with breadboard development and the Arduino IDE, and comes flashed with the Arduino Zero bootloader.

The Exen Mini wired up on a breadboard. (📷: Nerdonic)

There are 8 GPIO pins broken out from the microcontroller to standard breadboard-compatible through-hole headers, along with these there is also a 5-pin SWD connector exposed on the edge of the board. The Exen Mini can be powered directly from a 3.3V — 20V power supply via the power and ground pins, or via a standard 5V supply using the micro USB connector. All 8 of the broken out pins are capable of being used for PWM, while 6 are also capable of analog input using a 12-bit ADC.

The Exen Mini pin out. (📷: Nerdonic)

It’s arguable whether the Exen Mini is the “smallest” 32-bit development board, but it is small and cute, and actually rather capable for its size.

You can pick the Nerdonic Exen Mini up on Tindie for $13.20, with shipping starting at $5 for the first item to the United States. Additional boards ship free, and there is a volume purchase discount, with price per unit dropping down to $10 if you want 15 or more of the tiny boards.