deskthority

First, best regards to all. This is my first message in this forum and I've not see a "greetings" or "welcome" thread.

Next, my two little questions. Recently, I have brought an IBM model M122 keyboard. Just now, I'm using a standard model M, with an (cheap) active PS/2 to USB converter, which works fine (as an standard keyboard).

I've build a converter, with a promicro board and a female RJ45 connector. It seems ugly, but works almost perfectly [*]. Almost is the key. I've flashed a TMK firmware with no problems (also works with Soarer firmware); keys and layers are properly recognized, and scancodes (set 3) are correct. OS (ubuntu 20.04) detects the new keyboard and lists it with lsusb.

The first problem comes when restarting computer; Is detected as a keyboard, but doesn't works as expected: i.e. when a key is pressed, three random letters appear, enter key does nothing... But unplug and plug again USB connector, is like a charm, and everything behaves as expected.

Second problem is that some key combinations are not responding. CTRL+ALT+[left|right], used for change to left/right desktops on gnome DE, works fine. CTRL+ALT+[up|down] do not. CTRL+SHIFT+ALT+[left|right|up|down] (move a window to desktop) doesn't work at all. All of this key combinations are working in original model M, so I think M122 is fully capable to handle them. As a workaround, I'm mapping this combinations in upper layers; does the trick, but as emacs user, I need this kind of key combinations without mapping in these layers.

I'm a bit clueless with this problems. Reading forums, a teensy 2.0 is recommended for the converter, but there is a lot of people successfully using promicros for converters. I can buy a teensy, but is a bit expensive just for experiment. I think isn't a problem of
voltage (jumper J2 soldered) neither current.

Thanks in advance.

[*] I'm designing a more compact pcb, soldering the promicro to a RJ45 connector, but prior to printing, I need to know if there is a problem with the promicro and if I really need a teensy.

Welcome to DT. We tend to just show up much as you did, which is good, because I've some leads for you…

First, the Teensy vs Pro Micro question. I'm generally dubious about Pro Micros. I often point the finger at them, and I'm often right. Don't think that's likely in your case, though. See, when a Pro Micro isn't up to the job, it usually doesn't show up on the host at all: you've just got a dead keyboard. The other thing they sometimes do, is drop off regularly even when you're not touching the damn thing. That's what my Pro Micro powered AT was like. Really bugged me!

Could your power-on unresponsiveness be a Pro Micro thing? Maybe. It sounds a bit like one, but I can't guarantee a Teensy wouldn't do it too. Soarer converters (and TMK) are usually solid straight from power on, but there could be something going on with your host. I'd test the keyboard with another computer (especially a different OS entirely, just to mix things up) before trying a Teensy.

Now, for the rollover. You know Model Ms are all 2KRO, I expect. Sounds worse than it is. A well designed matrix can hide that limited rollover quite neatly. But the 122 keys aren't as well designed as the 101s. Here's your keyboard's matrix:


viewtopic.php?p=451764#p451764

Your problem is called blocking, and it's a matrix-level issue. Read all about it here. Keys get blocked when other keys mask them on the same rows and columns, and there are no diodes to prevent reverse current flows. Looking at those Up and Down keys, I see clashes with the mods. No converter can fix that.

I had an M122 for a while, and used it with my (Teensy powered) Soarer box with RJ45. But that matrix kept pissing me off. I just couldn't use the same chords on the M122 that worked fine on my SSK with the very same converter!, so I sold it when I could.

You're either going to have to switch to other keys, or save up for an NKRO Model F 122. (They are superb keyboards all round, built better and feel better, but cost as much as you might expect….)

Thanks for the clues, although are a bit disappointing.

Muirium wrote: 25 Jan 2022, 11:51 First, the Teensy vs Pro Micro question. I'm generally dubious about Pro Micros. I often point the finger at them, and I'm often right. Don't think that's likely in your case, though. See, when a Pro Micro isn't up to the job, it usually doesn't show up on the host at all: you've just got a dead keyboard. The other thing they sometimes do, is drop off regularly even when you're not touching the damn thing. That's what my Pro Micro powered AT was like. Really bugged me!

Could your power-on unresponsiveness be a Pro Micro thing? Maybe. It sounds a bit like one, but I can't guarantee a Teensy wouldn't do it too. Soarer converters (and TMK) are usually solid straight from power on, but there could be something going on with your host. I'd test the keyboard with another computer (especially a different OS entirely, just to mix things up) before trying a Teensy.

Probably you're right; I'll try keyboard with a powered USB hub and in a raspberry pi laying on desktop... Maybe USB cable isn't the best on earth.

Now, for the rollover. You know Model Ms are all 2KRO, I expect. Sounds worse than it is. A well designed matrix can hide that limited rollover quite neatly. But the 122 keys aren't as well designed as the 101s. Here's your keyboard's matrix:

I didn't expect to have a full NRKO, but al least the same performance as the 101 model. I guessed the matrix would be almost the same (ouch!).

Your problem is called blocking, and it's a matrix-level issue. Read all about it here. Keys get blocked when other keys mask them on the same rows and columns, and there are no diodes to prevent reverse current flows. Looking at those Up and Down keys, I see clashes with the mods. No converter can fix that.

I had an M122 for a while, and used it with my (Teensy powered) Soarer box with RJ45. But that matrix kept pissing me off. I just couldn't use the same chords on the M122 that worked fine on my SSK with the very same converter!, so I sold it when I could.

This are very bad news. Looking at the matrix, I think there will be a lot of key combinations doesn't work; CTRL+ALT is a common prefix in emacs commands. And, stupid question. A kind of mod like https://modelh.club/ won't work, right?

You're either going to have to switch to other keys, or save up for an NKRO Model F 122. (They are superb keyboards all round, built better and feel better, but cost as much as you might expect….)

The unit I bought was really cheap (60€, with a missing keycap) so I was happy of having a keyboard like my old M101, but with a bunch of extra keys (especially gaining a WIN key in a comfortable position). I'll give it a try, programming such a combinations in a separate layer.

Many thanks. Your help was very useful.

You’re welcome. Shame it’s just bad news, but here we are.

The matrix is the weakest link in the chain. No replacement controller can recover that lost signal. And no Teensy either.

Here’s a thread I wrote about this issue back on my M122. There’s some interesting leads there. None of them are easy. So much so, I just sold mine in the end!