Repurposing a Psion MC400 keyboard

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scottc

13 Jul 2016, 11:11

Hello everyone!

As I mentioned in the "stuff you just bought" thread, I recently got a nice, but very broken Psion MC400 laptop. Fortunately, the keyboard is absolutely pristine and feels fantastic. This thread will be an interactive exhibit of a strange man trying to reverse-engineer a keyboard for the first time.

The Psion MC400 is a British-made laptop from 1989. With apparently less than 1000 units made, this is a really cool collection piece. Of course, since it was 1989, no expense was spared and the keyboard is a G80-1600 manufactured by Cherry.

The keyboard is beautiful. It looks like the original MX 60%, and even has arrow keys! The keycaps are nice, thick Cherry doubleshot, but more grey than the normal Cherry keycaps so they can't really be mixed-and-matched with them. The switches are vintage MX clears -- which, I have to say, are really quite nice. I don't even normally like MX clears very much!

Here's a shot of it alongside my blue Alps Alps64 board:

Image

It's basically an ISO HHKB with arrow keys, guys! How cool is that?!

Since the laptop itself is probably beyond my repair skills, I've decided to repurpose the keyboard.

Step 1: Exposing the matrix!

Thankfully, the keyboard is connected to the mainboard via an 18-pin ribbon cable. This should make accessing the matrix pretty easy, and I don't need to reverse-engineer any weird 1989 protocols.

Here's a close-up of the ribbon:

Image

The ribbon is connected to the keyboard's PCB via a ribbon connector, meaning that this ribbon should hopefully be pretty easy to replace with something that gives me access to the pins for reverse-engineering the matrix (wow, that last part sounds really cool without context).

This cable looks like a good fit, but I have yet to check pitch etc:
http://www.aliexpress.com/item/39240900 ... 4495b56aa0

More info as I have time to do it!

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scottc

13 Jul 2016, 11:12

Reserved :shock:

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scottc

13 Jul 2016, 11:12

Reserved :shock:

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scottc

13 Jul 2016, 11:12

Reserved :maverick:

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Wodan
ISO Advocate

13 Jul 2016, 11:13

IMA SO JELLY

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scottc

13 Jul 2016, 11:19

:maverick:

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Stabilized

13 Jul 2016, 11:23

Are you planning to design a case for it if you get it working?

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ramnes
ПБТ НАВСЕГДА

13 Jul 2016, 11:31

Pretty sure it could fit in any 60% case with the help of a Dremel.

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scottc

13 Jul 2016, 11:47

I'm going to design a new case. It won't fit in a normal 60% case, the PCB is too big! I'd rather not modify the original PCB and I have no idea how I'd route the ribbon cable from the front of the PCB and still fit it in a case.

Plus, I want a nice HHKB-style case covering the places without switches!

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HzFaq

13 Jul 2016, 14:52

Nice work, looking forward to seeing how this turns out.

I was thinking of doing something similar but the up arrow/right shift position drove me up the wall (plus, my unit works and I didn't really want to kill it) so decided to keep the unit whole and just use the caps on my GH60.
edit - Actually, looking at it I think that's the FaceU I sold...

Image

What sort of condition is the rest of the case in? Mine has a chunk out of it, if you're willing to let it go I might try and use it to repair mine :D.

User avatar
scottc

13 Jul 2016, 16:01

That looks so nice! If all else fails, I'll just do what you did. I'm keen to give the arrows a go, I think they look really cool where they are, especially with the up arrow bump... we'll have to see how usable it is though. :D

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scottc

13 Jul 2016, 22:13

Anyone have any idea about the connector?

I completely missed your comment about the case, Hz. If I can't get the laptop working I'll gladly give you whatever parts you need.

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zedstarr

20 Jun 2022, 00:46

just managed to get a USB-MC400 keyboard working thanks to Frank Adams' Teensyduino sketch - the MC400 keyboard matrix is unique in that the On/Esc key has 2 dedicated lines (i.e. not shared with any other keys) to ASIC2 which is the custom chip that handles power on/off for the MC. Of the 18 pins in the connector it's a 9x9 matrix but with 2 pins dedicated to On/Esc it's 8x8 for the other 60 keys. This confused Marcel's python so I had to hack it around considerably to get it working!

video of USB-MC400 keyboard in action!
(Apologies, slow one-handed typing whilst holding the phone in the other hand :-) )
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IMG_20220619_105826_895.jpg
IMG_20220619_105826_895.jpg (1.92 MiB) Viewed 1686 times
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My Teensy LC sketch is here.
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Full keyboard matrix, including the case-mounted supplementary buttons (Task/Del/Home/End/PgUp/PgDn/LCD/Rec):
Screenshot from 2022-06-19 21-50-17.png
Screenshot from 2022-06-19 21-50-17.png (38.96 KiB) Viewed 1686 times

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