Home - rittme/nrfmicro GitHub Wiki

Welcome to the nRFMicro wiki!

This is a DIY drop-in Pro Micro controller replacement to convert wired Pro Micro-based keyboards to the true wireless ones.

Also check out the Jorne keyboard wiki about a keyboard I made to test this controller.

nRFMicro-1.2 with shield removed

Disclaimer

The board is based on the BLE-Micro-Pro board and nrf52 QMK firmware branch by sekigon-gonnoc. I've made my version using the cheapest nRF52840 bluetooth module available and the cheapest available components instead of rare japanese ones. I've also added Li-Po charger, USB Type-C and a physical ON/OFF switch on board. There's almost no room on a board this size so I had to remap GPIO pins to the closest physical positions (see Pinout). The rest is taken from the Adafruit Feather schematic almost verbatim (see Alternatives), considering that modules I use have different layout and different set of pins.

nRFMicro Features

  • Built in KiCad and fully autorouted with Freerouting (shouldn't be a problem to modify)
  • Same size as Pro Micro (18x33mm), has both MicroUSB and Type-C, Li-Po charger and BT 5.0
  • Runs full-featured QMK software (nrf52 fork) and ZMK, uses USB Mass Storage for firmware updates
  • Runs true wireless split keyboards over Bluetooth, does NOT need TRRS cables or receivers
  • Supports wired split keyboards via USB-C, MicroUSB and I2C/Serial extension cables

FAQ

  • Q. How many free GPIO pins does nRFMicro have?
  • A. 18 Pro-Micro pins at the sides, 8 pins at the bottom, 2 optional (XTAL) pins at the top - 28 pins total, see Pinout.
  • Q. Do you sell them?
  • A. No. It's a DIY project for kids. It's NOT suitable for mass production. See PCBA and Alternatives.
  • Q. Do I still need TRRS cable for the wireless split keyboard?
  • A. No, it uses wireless link between the halves. Cables are supported too (no charging over TRRS though).
  • Q. What's the battery life?
  • A. 2 weeks on a 100 mAh battery, a year on a 2500 mAh battery (or 2xAA). Charger is built in.
  • Q. Is there a lag while typing?
  • A. BLE devices can reach a latency of 1.3 ms, so no, there's virtually no lag.
  • Q. Can it switch between bluetooth devices?
  • A. Both QMK and ZMK support at least up to 5 bluetooth profiles.

Advanced FAQ

  • Q. Why there are no capacitors on the board (in the latest revisions)?
  • A. No room. It reuses capacitors from the bluetooth module (there are two large 4.7uF ones).
  • Q. Why the board is single sided, is it for the automated assembly?
  • A. It's NOT automated assembly compatible at all. It's just trying to be as thin as Pro Micro.
  • Q. I'm designing my keyboard specifically for your controller, where to get footprints?
  • A. Please stop. This board is nothing but a drop-in Pro Micro replacement, use Pro Micro footprints.
  • Q. What are the B+ and B-? Are they the same pins as RAW and GND?
  • A. Yes. It's 4.2V power input for the battery. Make sure RAW is separate from VCC on your keyboard.
  • Q. What are the EXT_VCC and EXT_GND? Are they the same pins as VCC and GND?
  • A. Yes. It's 3.3V output, sofware-controlled to save battery (RGB LEDs draw up to 1 mA each when off).
  • Q. What are you using to render pictures for GitHub?
  • A. I used kicadScripts both for pictures and gerbers, now I use Kikit.

MCU comparison

Board MCU Architecture Clock Flash RAM
nRFMicro nRF52840 32-bit Cortex M4 64 Mhz 1 MB 256 kB
Pro Micro ATmega32u4 8-bit AVR 16 Mhz 32 kB 2.5 kB
Bluepill STM32F103C8T6 32-bit Cortex M4 72 Mhz 64 kB 20 kB
Proton-C STM32F303CCT6 32-bit Cortex M4 72 Mhz 256 kB 40 kB

Size comparison

Board Size (mm) Comment
nRFMicro-1.1 18x33x6.35 height is limited by double-sided SMT and topmount USB-C
Proton-C 18x33x4.80 limited by topmount USB-C height
nRFMicro-1.2 18x33x4.50 midmount USB-C, limited by shielding height
Pro Micro 18x35x3.75 limited by topmount Micro USB height
nRFMicro-1.3 18x33x3.45 no shielding, limited by ceramic antenna and 1.6 mm PCB
nice!nano 18x33x3.20 limited by midmount USB-C for 1.6 mm PCBs
nRFMicro-1.4 18x34x3.20 no shielding, 0.8 mm PCB, limited by midmount USB-C

nRFMicro 1.2 with 1.6 mm PCB and midmount USB connector, shielding (on the last picture) adds 1+ mm so better remove it.

picture-sizes

Preassembled boards

If you're not too skilled at soldering there are stores that sell compatible wireless controllers (I am not affiliated in any way):

See Alternatives article about alternative boards.

References