Project for an IBM M122 keyboard controller
This is a project that replaces the original part from IBM with a nice modern solution. It features a nRF52840 microcontroller and allows to use the keyboard via USB connector, or via Bluetooth.
The firmware is based on the ZMK project.
Beside the assembled PCB you require:
- A matching IBM Keyboard
- An external LiPO cell - the unit was designed with a LP103048JU 1.500 m Ah cell in mind
- One 8 pin connector for the flat flex coming from the keyboad 5-520315-8 from AMP DigiKey P/N 5-520315-8-ND
- One 20 pin connector for the flat flex coming from the keyboad 7-520355-0 from AMP DigiKey P/N A144436-ND
You need a debug adapter (JLink) with 6 pin Tag-Connect for the initial flash programming of the board
When ordering the pcb from JLC you need to specify
- Via Covering Epoxy Filled & Capped
- Min via hole size 0.2 mm
- Use the nrf-Flash-Tool to flash the bootloader to the nrf52840
- Use drag-and-drop of the uf2 build output to flash the keyboard firmware
push and pull_request trigger a github-action to build the firmware. To locate the build output
go to the Actions tab and open the respective workflow run. There you find a link to the artifacts
generated by the run. You can download it and unpack the .zip archive to access the .UF2 file.
Set the zmk project up in a seperate directory as described in Toolchain Setup. Go to the zmk base directory, then run
cd app
west build --board nrf52840_m122 . -- -DZMK_EXTRA_MODULES=(..)/m122_keyboard/
Replace (..) with the path of this project. Note, that the tilde (~) is not eveluated correctly in that pathname.
The project uses a modified Adafruit bootloader.
You might want to test the basic electric functionality of the PCB. To do so, flash the firmware and connect the PCB to a computer´s USB port. To view detailled event codes start
sudo evtest
Select your M122 controller as event source. Now, you can short individual rows and columns. Expected results are given for German keyboard layout.
| Row | Column | Keycode |
|---|---|---|
| 1 | 16 | KEY_KP0 |
| 1 | 8 | KEY_B |
| 2 | 8 | KEY_V |
| 3 | 13 | KEY_RIGHTBRACE |
| 4 | 5 | KEY_Q |
| 5 | 9 | KEY_6 |
| 6 | 12 | KEY_F5 |
| 7 | 1 | KEY_PPLUS |
| 8 | 15 | KEY_APOSTROPHE |
| 2 | 2 | KEY_KP1 |
| 2 | 3 | KEY_CAPSLOCK |
| 1 | 4 | KEY_LEFTSHIFT |
| 1 | 20 | KEY_ENTER |
| 1 | 19 | KEY_KPCOMMA |
| 2 | 18 | KEY_KP2 |
| 2 | 17 | KEY_INSERT |
| 4 | 15 | KEY_P |
| 6 | 14 | KEY_9 |
| 4 | 11 | KEY_F7 |
| 3 | 10 | KEY_F20 |
| 7 | 6 | KEY_S |
| 7 | 7 | KEY_D |