nRF52840 Pro Micro Controller

The nRF Pro Micro is a cheaper alternative to the awesome nice!nano controller. It is a Pro Micro drop-in replacement board that allows making any Pro Micro based board into a wireless one.

Features

• Fully compatible with the nice!nano – uses the same ZMK firmware
• Powerful Nordic nRF52840 microcontroller with 256 KB RAM and 1 MB flash
• 21 GPIO pins
• Drag and drop flashing using the UF2 bootloader
• Built-in lithium polymer battery charger
• Just 3.3 mm thick thanks to a mid-mounted USB-C socket
• Gold plated (ENIG) finish, black solder mask
• Includes 2x 13 pin + 1x 3 pin header pins (you will usually need to shorten them to 12 pins)

Notable differences to the nice!nano:

• Apparently a higher power consumption – might not be best suited for use with tiny (~100 mAh) batteries
• Doesn’t have an on-board reset button. Instead, the controller can be reset by shorting the RESET pin (pin 4 from the top right) to GND (pin 3), for example by using tweezers

Flashing

The built in UF2 bootloader makes flashing very easy – no programmer necessary. Just reset the board twice in quick succession (e.g. by double-tapping the reset button on the keyboard) to enter the bootloader mode which will present the board as a USB Mass Storage device (think “USB flash disk”) – just drag and drop the firmware .uf2 file to the disk and it will be flashed automatically.

See the ZMK Getting Started guide to find out more about customizing the firmware for your board.