Using QMK with one of the ortholinear contoured keyboards manufactured by PCD Maltron Ltd by modding it with a DIY replacement controller.
This work here in no way officially associated with PCD Maltron Ltd and comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. Modifying your Maltron keyboard as described below will certainly void your warranty and may e.g. cause damage to your keyboard. Proceed at your own risk!
Make example for this keyboard (after setting up your build environment):
make handwired/dqz11n1g:default
PCD Maltron Ltd manufactures ergonomic keyboards that appear to be hand-wired internally. For the Maltron DQz11N1G-DE keyboard that I happen to own, the keyboard matrix is wired to a 34-pin DIL connector. This makes it rather easy to replace the proprietary controller-board with a self-made board based on the QMK firmware.
I don't really like the default layout of my Maltron DQz11N1G-DE keyboard, and modding it to work with QMK allows me to adapt it to my needs. It especially allows for the two space keys to assume different roles, thereby creating an additional easily reachable thumb-key.
Due to supply chain problems, I decided to base this on an Arduino-compatible Pro Micro board which is still easy to source.
Unfortunately pin-count of the DQz11N1G-DE's keyboard matrix is way beyond the Pro Micro's available I/O pin count. I'm using three 8-bit shift-registers (SN74HC165 ) to connect the 19 columns of the keyboard matrix for readout. Due to diode direction in DQz11N1G-DE we also need 19 pull-down resistors one for each of the utilized shift-register inputs.
This is a design sketch of the replacement board this is based on. Note how we need a custom matrix.c source file to deal with the shift register based keyboard readout.
This is how the assembled controller board looks like, on the right side you see the original PIC-based controller the keyboard ships with.
Inside of the keyboard after installing the new controller board:
(Not visible in the photo: I drilled hole into the keyboard above the USB connector for a reset switch to simplify flashing controller firmware)