after an extremely stressful year I'm trying to resume normal life and try to have a bit of time for hobbies. To kick things off I wanted to something relatively simple. The QL keyboard looks great but trying to type on it is frankly quite painful. So the idea was born to try to hook up a USB keyboard to the QL. Easiest way to go about it was to get inspiration from an existing design. The Jurgen Falkenberg PC keyboard adapter was an interesting approach to the problem so I started to see how to bring that idea to the modern world.
I ended up throwing together an analogue crosspoint switch (Zarlink MT8808), an Atmega328P microcontroller and a USB host controller chip (MAX3421E). There's an existing USB host library for Arduino and it was a straightforward job to adapt it to the job of controlling the crosspoint switch based on input from the USB keyboard. The crosspoint switch matrix chip interfaces with the 8049 chip on the QL main board emulating the keyboard membrane switches. The PCB sits inside the QL in the 8049 socket. Like in the Jurgen Falkenberg design, the 8049 chip needs to be removed from its socket and seated on the keyboard adapter PCB.
The first prototype batch of PCBs arrived today from China so I was eager to solder one together to show you guys. My soldering skills leave a lot to be desired but I somehow managed to get even the fine pitch SMD components on the board successfully. Having never worked with 0603 footprint components it was rather slow going and it took me around three hours to solder everything in. Next one is going to be faster (I hope!)
I'm open sourcing the design including Eagle design files and the associated software for the microcontroller so if somebody wants to enhance the solution, please feel free to contribute! Details to follow...
Also, the minimum order for the PCBs was five pieces and for some reason the factory actually sent seven pieces. If anyone is interested in trying it out once I have tested the board I would be happy to solder one up and send over for testing. I ordered enough components from Mouser for five boards initially. Some of the components are a tad on the expensive side bringing the total cost for the board up to around 32€.
One thing I have not gotten around to yet is support for different keyboard layouts. Currently it is Finnish only
But, I'm willing to work together with anyone willing to help in adding support for other layouts, obvious starting points being the UK and German layouts.Since this is a hobby project for me, I'm not looking to make money on this, it is not going to be a commercial product and there will definitely NOT be any kind of warranty and/or service for it!
I'm hoping to post a video of the keyboard in action in the near future.
Well, sorry for the long post but I hope someone finds this interesting.
By the way, this is the first PCB I have ever designed so please go easy on the critique...
Kind regards,
Petri
