Teensifying my old Maltron

Piers Cawley · 26 Dec 2012, 19:38

I have an old 3d Maltron keyboard that has an old AT connector and nothing but macs in the house, so I need to do a USB conversion. I would just do a straightforward AT -> USB conversion, but I want to be able to remap the 'shift lock' key, which appears to be managed by the Maltron firmware. So, in a moment of "Leap, and the net will appear!" insanity I desoldered the old ribbon cable and hooked everything up to a Teensy 2.0++ and started messing about with the TMK firmware.

And... that's where I'm stuck. The matrix appears to be 8 rows of 16 columns and the only anti-ghosting diodes are on the various modifier keys. There are also diodes where the ribbon cable taps the rows. So I have:

Row(N) -->|-- PF(N)

Col(0-7) ---- PD(0-7), Col(8-15) ---- PC(0-7)

But for the life of me, I can't work out how to tweak the matrix.c to read anything.

Has anyone successfully put a Teensy in a Maltron?

Jim66 · 27 Dec 2012, 16:38

Sorry, I can't think of anyone that has done this.

I know that Maltron have?

http://deskthority.net/news-reviews-f4/ ... t4043.html

Maybe worth giving them a call, you never know, they might be able to give you some answers?

hasu · 30 Dec 2012, 16:49

Post pics or schematic and your code.
I may be able to help you somehow.

Piers Cawley · 02 Jan 2013, 23:33

I thought I'd tried every combination of methods of scanning the matrix, but it seems I missed one, or I needed to introduce a little more delay. I ended up reading the columns using the Teensy's built in pull-up resistor and pulling each row low in turn.

I could have sworn I'd already tried that, but maybe I hadn't, or maybe adding _delay_us(100) after resetting the rows was the magic I was missing before. Now I've got the basic scanning part worked out I can start sussing out which keyswitches need replacing, and where/whether I need to add a few anti-ghosting diodes.

I plan to write this up properly later.

While I'm here, what firmware do people recommend as a good starting point for hacking? I've started with the tmk package and aim to start off with a basic Maltron layout and pinch ideas from Neo and ergodox for 'deeper' layers (there's 8 keys per thumb cluster on this keyboard and once I've stopped them all ghosting, I intend to nick at least the arrow keys for use as modifiers).

Also, at least one of the keyswitches is playing up, do cherry blacks tend to respond to disassembly, blowing on the bits and then reassembly, or am I better off getting a new unit and trying not to melt the keyboard case with my exceedingly rusty soldering skills?

This is such fun; why didn't I do it before?

vivalarevolución · 03 Jan 2013, 00:32

Piers Cawley wrote:
Also, at least one of the keyswitches is playing up, do cherry blacks tend to respond to disassembly, blowing on the bits and then reassembly, or am I better off getting a new unit and trying not to melt the keyboard case with my exceedingly rusty soldering skills?

This is such fun; why didn't I do it before?

Are you asking about changing the switches in your Maltron from Cherry Blacks to a different kind of switch? Because I'm currently in the process of doing so, and I can offer some advice. I changed my switches without having to re-solder the switches.

Piers Cawley · 03 Jan 2013, 11:27

Right now I'm thinking of changing blacks for blacks on the keys that aren't registering (the maltron has more keys than I use, so if I can swap one of those in to get me a working right shift then I'm good for now), but in the medium to long term I'd be interested in swapping blacks for browns or blues.

Or, to put it another way: yes, that advice would be very welcome.

jesse · 03 Jan 2013, 20:05

Piers, I found the Humble Hacker firmware incredibly flexible.

vivalarevolución · 05 Jan 2013, 00:39

Piers Cawley wrote:Right now I'm thinking of changing blacks for blacks on the keys that aren't registering (the maltron has more keys than I use, so if I can swap one of those in to get me a working right shift then I'm good for now), but in the medium to long term I'd be interested in swapping blacks for browns or blues.

Or, to put it another way: yes, that advice would be very welcome.

I have chronicled the first part of my Maltron switch change without having to desolder and resolder the wires, but rather by opening up the Cherry MX black switches. Currently, I am waiting on the MX Clear switches I bought from 7bit in the Cherry MX group buy to arrive and put in new springs and stems. It took me a few hours to do the whole keyboard while I watches some television.

http://deskthority.net/workshop-f7/anyb ... t4675.html

If you have any questions, let me know. There are many videos and threads around about how to open the switches and put in different springs.

Piers Cawley · 07 Jan 2013, 01:20

Thanks for the pointers to popping the switches. I ended up popping about three iffy keys where disassembly, a squirt of air and reassembly did the trick, however one switch (right shift, so not something I can live without) didn't recover, so I sacrificed one of the keys from the middle (which I never use) for the cause and now all the keys that matter are working.

There's one more potential bit of fiddling with solder because this keyboard currently has row 3, col 1 (counting from top and left) mapped as an extra single quote key, but it wasn't done in the controller, it's done by running a pair of wires across from the right hand side, so it scans as the normal single quote. I don't know whether to gnash my teeth in frustration, or stand in awe. You can certainly see why these things are so expensive, the wiring loom is terrifying. Thin, thin wire, wrapped and soldered before the bracket for the base was glued in place so getting an iron in to the f-keys row is a daunting prospect. If I do decide to regularise the matrix, I think I'll get rid of the to row and move f1-10 onto FN-# and give up the top row.

So...time to build me a key map.

Piers Cawley · 07 Feb 2013, 00:54

Hmm... how did this happen? One minute I'm just thinking replacing the controller in the Maltron, the next I've ordered a bunch of MX Browns from 7bit and, because enough keyswitches are up the spout, the point to point wired matrix is both beautiful and confusing, I've attacked the underside of the board with a diagonal cutter and am planning on soldering in a new matrix, just as soon as the keys and the self-fluxing solderable magnet wire I've ordered arrives.

I've even worked out a soldering scheme that involves popping all the switches and insertion 1N4148 diodes everywhere.

Photos will follow, but it's nearly midnight and I've got to go to work tomorrow. What's the going rate for desoldered and checked MX blacks?

vivalarevolución · 08 Feb 2013, 04:17

Piers Cawley wrote:Hmm... how did this happen? One minute I'm just thinking replacing the controller in the Maltron, the next I've ordered a bunch of MX Browns from 7bit and, because enough keyswitches are up the spout, the point to point wired matrix is both beautiful and confusing, I've attacked the underside of the board with a diagonal cutter and am planning on soldering in a new matrix, just as soon as the keys and the self-fluxing solderable magnet wire I've ordered arrives.

I've even worked out a soldering scheme that involves popping all the switches and insertion 1N4148 diodes everywhere.

Photos will follow, but it's nearly midnight and I've got to go to work tomorrow. What's the going rate for desoldered and checked MX blacks?

Sold the MX blacks from my Maltron for about $USD 0.30 per switch. Probably could get more that if you want.