# DQz11N1G

![DQz11N1G](https://u.cubeupload.com/ddklg/OPBN5q.jpg)

Using QMK with one of the ortholinear contoured keyboards manufactured by [PCD
Maltron Ltd](https://www.maltron.com) 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!

* maintainer: [David Kuehling](https://github.com/dvdkhlng/qmk_firmware_dqz11n1g)
* Hardware Supported: Maltron DQz11N1G with a replacement controller board
  assembled as described below.  The work here is based on a German version
  of the keyboard: DQz11N1G-DE.  I assume, but don't know for sure, that
  minor or no changes at all are required to make this work on different
  language versions of the keyboard.
* Hardware Availability:
  * [PCD Maltron Ltd](https://www.maltron.com), for the original keyboard
  * 1x [Arduino Pro Micro](https://www.sparkfun.com/products/12640)
  * 3x shift register [SN74HC165](https://www.ti.com/product/SN74HC165)
  * 3x ceramic blocking capacitors (100 nF) one for each shift register
  * 1x DIL connector 2 rows a 17 pins.
  * 19x pull-down resistors (10k Ohm),
  * 4 LED current limiting resistors (not sure about the correct resistance,
    using 470 Ohm here)

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

    make handwired/dqz11n1g:default

## In Detail

[PCD Maltron Ltd](https://www.maltron.com) 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.

### Internal Details of Keyboard Matrix and DIL Connector

![DQz11N1G-DE keyboard matrix](https://u.cubeupload.com/ddklg/OJFue6.jpg)

![DQz11N1G-DE keyboard matrix connector](https://u.cubeupload.com/ddklg/fjFXeL.png)

### Replacement Keyboard Controller Board

Due to supply chain problems, I decided to base this on an
Arduino-compatible [Pro Micro](https://www.sparkfun.com/products/12640)
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](https://www.ti.com/product/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.

![Sketch of Keyboard Controller Board](https://u.cubeupload.com/ddklg/GBZgSf.png)

This is how the assembled controller board looks like, on the right side you
see the original PIC-based controller the keyboard ships with.

![The assembled controller next to the original controller the keyboard ships with](https://u.cubeupload.com/ddklg/KLYF2V.jpg)

Inside of the keyboard after installing the new controller board:

![Installed controller](https://u.cubeupload.com/ddklg/Br0aiF.jpg)

(Not visible in the photo: I drilled hole into the keyboard above the USB
connector for a reset switch to simplify flashing controller firmware)