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A 4x4 keypad kit made and KPRepublic on AliExpress. This is a chopped off version of the jj40 with rearranged keys.

Keyboard Maintainer: QMK Community
Hardware Supported: Atmega32A
Hardware Availability: AliExpress

Make example for this keyboard (after setting up your build environment):

make jj4x4:default:program

See build environment setup then the make instructions for more information.

Note that this is a complete replacement for the firmware, so you won't be using Bootmapper Client to change any keyboard settings, since not all the USB report options are supported.

In addition you may need the AVR toolchain and bootloadHID (GitHub repo) for flashing:

For macOS:

$ brew cask install crosspack-avr
$ brew install --HEAD

For Linux:

$ sudo apt install libusb-dev
$ wget
$ tar -xzf bootloadHID.2012-12-08.tar.gz
$ cd bootloadHID.2012-12-08/commandline
$ make
$ sudo cp bootloadHID /usr/bin

In order to use the ./util/ script, which can reboot the board into the bootloader, you'll need Python 2 with PyUSB installed:

$ pip install pyusb

If you prefer (or are having issues with a program flash), you can just build it (make jj40:<keymap-name> and flash the firmware (.hex file) directly with bootloadHID if you boot the board while holding down 8 (second from top, second from left, with usb plug is at the top) to keep it in the bootloader:

$ make jj40
$ bootloadHID -r jj4x4_default.hex

For Windows 10: Windows sometimes doesn't recognize the jj4x4. The easiest way of flashing a new layout is probably using HIDBootFlash.

  1. Go to Windows Device Manager and find the keyboard (plug it in while holding down 8 (second from top, second from left, with usb plug is at the top)). It can be found under Human Interface Devices or under Keyboards.
  2. Go to properties and the Details tab to find the hardware ID. You want the VID and the PID (code after the underscore). Plug them into HIDBootFlash and hit Find Device.
  3. Use make jj4x4:<keymap-name> to generate the .hex file in the qmk basis folder. Select the .hex file in HIDBootFlash and press Flash Device.


  1. Try plugging the board in while pressing 8 (usb plug at top, second from top, second from left). This will force it to boot only the bootloader without loading the firmware. Once this is done, just reflash the board with the original firmware.
  2. Sometimes USB hubs can act weird, so try connecting the board directly to your computer or plugging/unplugging the USB hub.
  3. If you get an error such as "Resource Unavailable" when attemting to flash on Linux, you may want to compile and run tools/usb_detach.c. See tools/ for more info.
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