Pro-Micro compatible. Uses Lairdtech BL654 module, assembled board sells for about $36. Schematic is open, but no PCB gerbers available for this board. Runs QMK firmware.
- https://nogikes.booth.pm (Online shop, sells for 4000 JPY, about $36)
Does NOT support wired connection (uses nRF52832-based E73-2G4M04S1B module, so no hardware USB) but has Li-Po charger on board (USB is used only for charging). Runs its own firmware but it's possible to run full QMK (nrf52 branch) on it, see jian_bm. The board is much longer than a regular Pro Micro so it's not really suited for the small keyboards such as Corne and Jian (Iris is fine). No indicator LEDs.
- https://github.com/jpconstantineau/NRF52-Board (hardware)
- https://github.com/jpconstantineau/BlueMicro_BLE (firmware)
- https://github.com/joric/qmk_firmware/wiki/jian_bm (alternative firmware)
Adafruit Feather nRF52840 Express
NOT Pro-Micro compatible. Uses MDBT50Q module. Schematic and PCB are open source. Sells for $24.95. No QMK firmware available.
- Adafruit Feather nRF52840 Express Downloads
- Adafruit Feather nRF52840 Express Schematic
NOT Pro-Micro compatible. Open source, nRF52840-based, assembled board sells for about $15. No module is used, nRF52840 soldered on board. Meets the Adafruit Feather specification in dimensions and pinout. No QMK firmware available.
Arduino Nano 33 BLE
NOT Pro-Micro compatible (rather, Nano-compatible), does NOT have a Li-Po charger on board. Sells for $19 on arduino.cc. Uses NINA B306 module (nRF52840-based). It's much longer than Pro Micro and power pins are on the other edge of the board from the MicroUSB connector, also power pins are a little bit scrambled, note RST, GND and VCC locations. No QMK firmware available.
Not a board, but rather an STM32 microcontroller with BLE/ZigBee/Thread/802.15.4 support.
Two cores: Cortex-M4 (64 Mhz) and Cortex-M0+ (radio, 32 Mhz), USB, 1M Flash, 256Kb RAM.
- https://www.aliexpress.com/item/32989918160.html ($62 for P-NUCLEO-WB55 SDK).
Not widely available but have a higher chance to be merged into QMK (better licence than Nordic). No QMK firmware available.
Used in nRFMicro, nRF52840-based, 13x18mm (13mm is a borderline for Pro Micro), sells for $5-$7 (sometimes can be found for $3.50).
Used in Adafruit Feather nRF52840 Express, nRF52840-based, 10.5x15.5mm, sells for $8.89
Used in BLE-Micro-Pro, nRF52840-based, 10x15mm, sells for $15.97
nRF52840-based, 18x13.5x1.6mm, sells for $10.11
- Aliexpress: https://www.aliexpress.com/item//32868365660.html ($10.11 for 1 pcs, ~$7 in bulks)
nRF52840-based, 13.7x14.7mm, sells for $8.53 ($6 in bulks)
- https://www.aliexpress.com/item//32984570877.html ($8.53)
- https://www.aliexpress.com/item//32982453902.html ($59.27 for 10 pcs)
Mind that anything that's wider than about 14mm won't fit on a Pro Micro footprint. This one ought to be 13.7x17.4mm and it fits just fine, and it's about the cheapest on Aliexpress ($8.53 total) but there's NO USB.
Please note that there is NO USB on this SKYLAB SKB501 module, and no USB pins in the pinout albeit it's nRF52840, so I would very much NOT recommend it for anything.
nRF52840-based, either 10.0 x 11.6 mm for B3x1 10.0 x 15.0 mm for B3x2 (either way, it's not larger than 10 mm on the narrower side). Lots of underside pins. Used in Arduino Nano-33 BLE.
SparkFun Artemis Module
An interesting module by SparkFun (NOT nRF52840-based, just Cortex-M4F with BLE 5.0). No hardware USB (?) All breakout boards are UART/CH340-only.