Modules
Used in nRFMicro, nRF52840-based, 13x18mm (13mm is a maximal possible width for Pro Micro), sells for $5-$7 (sometimes can be found for $3.50 and $3.20 even). 30 free GPIOs including XL1/XL2.
E73-2G4M08S1CX schematic (with the IPEX antenna) is IDENTICAL. Does not need an extra XTAL or anything.
nRF52833-based (half the Flash, so no Python). Lacks pin 1.11 so it's not 100% compatible. Also no DCCH so no HV mode. Other changes for nRF52833 module is that 1.10 is now 0.25 (blue led) and 1.13 is now 1.05 (standard gpio).
Used in Adafruit Feather nRF52840 Express, nRF52840-based, 10.5x15.5mm, sells for $8.89
- https://www.ebay.com/itm//173373877282
- https://www.raytac.com/upload/download_files/1bca545683ea4caf48e1ec796c09b9d9.pdf
Used in BLE-Micro-Pro, nRF52840-based, 10x15mm, sells for $15.97. There also BL651 modules without SMA socket.
- https://fccid.io/SQGBL654/User-Manual/Users-Manual-3905952.pdf
- https://www.lairdconnect.com/bl654-ble-modules-and-development-kits
- https://www.mouser.com/datasheet/2/223/BL654_Datasheet_v1_2-1479813.pdf
- https://www.mouser.com/Search/Refine?Keyword=bl654
nRF52840-based, 18x13.5x1.6mm, sells for $10.11 ($5 on alibaba). Very interesting module! Has xtal on board. Theoretically fits Pro-Micro with a little bit of filing. Not too many underside pins. Used in Corne-ish Zen.
- Aliexpress: https://www.aliexpress.com/item/32868365660.html ($10.11 for 1 pcs, ~$7 in bulks)
- Shielded version: https://www.aliexpress.com/item/32868002366.html
- Alibaba: https://holyiot.en.alibaba.com/
- Schematic: http://www.holyiot.com/tp/2019042311405478395.zip
Note that Holyot already has the DC-DC inductivity soldered in so you don't need 3V LDO to run MCU from internal DC-DC. If you want to run off a raw module, don't buy E73, buy Holyot (it also has an external crystal, XTAL).
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)
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.
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.
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.
- https://store.arduino.cc/usa/nano-33-ble
- https://www.u-blox.com/sites/default/files/NINA-B3_DataSheet_%28UBX-17052099%29.pdf
nRF52840-based, costs $3-$4. Too large for the Pro Micro footprint (17.4mm wide, need 13mm).
- https://www.aliexpress.com/item/4000101935456.html
- https://www.minew.com/download/nRF52840%20Module%20MS88SF2%20Datasheet.pdf
There are also MS88SF3 modules, they are smaller but but they're impossible to solder with an iron.
nRF52822-based (BT 5.2 SoC, same as nRF52840 but half the ram, half the flash and with BT 5.1 direction finding). Seems too large for the Pro Micro footprint (685 mil = 17.3 mm, need 13mm).
- https://www.aliexpress.com/item/33011597378.html ($8.48 for 2 pcs)
nRF52822-based, no shielding. Too large for the Pro Micro footprint (size 24.3 x 17.5 x 1.8mm with Antenna, width 17.5mm, need 13mm).
- https://www.aliexpress.com/item/4000712170592.html ($11.23 for 2 pcs)
Something obscure from the seller of Supermini ICBuy. Costs the same as Supermini nRF52840. Claims to support ZMK (NRF52840 Core, Bluetooth module with ZMK support Tool IO Full Lead Out). Untested.
You can unofficially (licensing is expensive) code/program a keyboard using CC245x modules (same as used in HM-10/HM-11).
- World's smallest keyboard: https://github.com/joric/cc2540-keyboard
Video:
An interesting module by SparkFun (NOT nRF52840-based, just Cortex-M4F with BLE 5.0). No hardware USB so it kind of sucks a little bit. All breakout boards are UART/CH340-only.
We did it, everyone! SparkFun’s Artemis Module has earned approval from the Federal Communications Commission (FCC) and Industry Canada (IC), making it the first open-source, US-manufactured, FCC/IC-certified BLE module on the market.
- https://www.sparkfun.com/news/3082
- https://github.com/sparkfun/SparkFun_Artemis
- https://cdn.sparkfun.com/assets/5/c/b/3/c/SparkFun_Artemis.pdf
- https://learn.sparkfun.com/tutorials/designing-with-the-sparkfun-artemis/all
UART means you can control them from QMK as daughter modules to the wired controller. They understand a set of modem-like commands sent via the standard terminal (you just need a couple of free GPIO pins), handle Bluetooth pairing and send key codes via the Bluetooth HID protocol.
- QMK-compatible modules: https://beta.docs.qmk.fm/using-qmk/hardware-features/feature_bluetooth
- Turning HC-06 into RN-42 Bluetooth 2.0 HID module: https://imgur.com/a/1LHSR
- Turning HM-10, HM-11 into Bluetooth 4.0 HID modules: https://imgur.com/a/KWmz6
- Turning NRF51822 into Bluetooth 4.0 HID module: https://imgur.com/a/ej9hD
It's probably also possible to use Adafruit Bluefruit LE UART Friend HID firmare for nRF51822:
- https://github.com/adafruit/Adafruit_BluefruitLE_Firmware
- https://learn.adafruit.com/introducing-the-adafruit-bluefruit-le-uart-friend/software
- https://learn.adafruit.com/introducing-the-adafruit-bluefruit-le-uart-friend/hidkeyboard
A brief comparison of nRF52840 modules from Alibaba sorted by the width of their smallest module with antenna and certs (smw), ssmw is the same but with side pins (taken from here).
| company | volume_usd | volume_count | ratings | rating | response_rate | smw | ssmw |
|---|---|---|---|---|---|---|---|
| Holyiot | 5000 | 34 | 7 | 5 | 95.2 | 13.5 | 13.5 |
| Skylab | 270000 | 74 | 0 | 0 | 90 | 13.7 | 13.7 |
| Minew | 110000 | 172 | 48 | 4.8 | 93.9 | 17 | 17 |
| Thingo | 50000 | 89 | 21 | 5 | 86.9 | 12 | 12 |
| Feasycom | 120000 | 74 | 0 | 0 | 90 | 10 | 10 |
| Ebyte | 410000 | 247 | 40 | 4.8 | 94.4 | 13 | 13 |
| RF-star | 4000 | 35 | 4 | 5 | 100 | 15 | 15 |
| Dingcheng | 50000 | 96 | 39 | 4.9 | 96.5 | 13 | 13 |
| Raytac | - | - | - | - | - | 10.5 | - |
| ShenzhenWireless-Tag | 3000 | 9 | 2 | 5 | 96.2 | 18.4 | 18.4 |