Keyboard switch-cap ID for a project.

[CaptCarrot]

Hi guys, been a while.  I'm hoping someone on here can help.

I am in the process of cobbling together a Raspberry Pi "thing".

I am planning on building it inside an old keyboard (is going to need a bit of work I know).

Now here's the thing, I am planning to use an old Archimedes (Acorn) keyboard.  To accomplish this I am either going to have to convert the keyboard from it's proprietary format or replace it's gubbins.  Now in that regard, the one thing I really like is the Caps Lock, Num Lock and Scroll Lock LED's in the keys and not in the top right.

I see it as I have several options.

• Take a normal keyboard, mod the keys and re-wire the LED's and transplant the gubbins.
• Use the existing keyboard and modify the output, something along the lines of this - http://blog.tynemouthsoftware.co.uk/2013/06/usb-keyboards-for-sale.html - or this - http://denki.world3.net/beebkb.html.
• The third option would be to keep the mechanics, but swap the membranes.  Dunno if that will work at all.

With the first option, I could save myself a bit of hassle if I could find a PC keyboard that has the same style key-caps as the donor.

With that in mind, could someone cast there eyes over these pictures and tell me if they think there is a possibility there is a suitable PC keyboard.

or comment on my other ideas or supply a different one.

 http://www.classicacorn.freeuk.com
A310 keyboard - http://www.classicacorn.freeuk.com/32bit_hardware/a310kboard/a310kboard.html
A4000 keyboard - http://www.classicacorn.freeuk.com/32bit_hardware/a4000kboard/a4000_keyboard.html

[BlueBär]

I would recommend rather that A310 than the A4000 because it has a PCB instead of just a membrane. It also has mechanical switches, however they aren't completly modular (they need a PCB to work).
You can solder wires directly on the PCB I think (the quality of the pics is too low to be certain), and then do the "direct wiring" method with the difference being that you have to keep the PCB instead of only using the plate. If you want to know more about direct wiring, search the making stuff together subforum, there's a lot of information about it there.

Out of interest, why do you want to use one of those keyboards?

[IvanIvanovich]

If you find a board that has the controller on a separate PCB than the matrix, you can disconnect it and wire the switch matrix PCB directly to gpio on the rpi and set it in software. There are some good candidates in MX keyboards like this that also happen to have some more spacious casebodies that you could get a pi into without much more effort than making some holes for the i/o ports.

[CaptCarrot]

I would recommend rather that A310 than the A4000 because it has a PCB instead of just a membrane. It also has mechanical switches, however they aren't completly modular (they need a PCB to work).
You can solder wires directly on the PCB I think (the quality of the pics is too low to be certain), and then do the "direct wiring" method with the difference being that you have to keep the PCB instead of only using the plate. If you want to know more about direct wiring, search the making stuff together subforum, there's a lot of information about it there.

Out of interest, why do you want to use one of those keyboards?

As it happens I am looking at an A5000 keyboard (same as the A4000 I think) right now.  I'll look at the direct wiring method.

As for why:

• Because it is going to be running RISCos, and I want it to be a take on the old machines.
• The challenge

[edit]

Assuming the spacings are the same, could one swap out the Archimedes membrane and controller board for a PC one?


[/edit]

If you find a board that has the controller on a separate PCB than the matrix, you can disconnect it and wire the switch matrix PCB directly to gpio on the rpi and set it in software. There are some good candidates in MX keyboards like this that also happen to have some more spacious casebodies that you could get a pi into without much more effort than making some holes for the i/o ports.

I might look into that - but that is mostly covered under the Linux based distro's.  I'm less sure how to accomplish this/whether it's possible under RISCos.



On the subject of the key caps - do any of those images (poor quality though they are) suggest that they may take key caps from a PC keyboard, like a Model M or similar?

[CaptCarrot]

According to page 30 (manual section 2-4) of the Service Manual, the keyboard will either be Panasonic or Keytronic

Keyboard
The computer may be fitted with either one of two keyboards:

• Panasonic (fitted on most models)
• Keytronic (on some early models).

Both keyboards are identical on the exterior; they only differ internally, in that they have different PCBs.

...

The PCB in the Keytronic keyboard is fixed to the top moulding by six No. 6 x 0.25" screws.

The PCB in the Panasonic keyboard is fixed to the top moulding directly by four screws, and also by means of two metal brackets (with four screws and washers).

For the Panasonic keyboard, first remove the two screws and washers fixing the brackets to the top moulding, then remove the  remaining screws fixing the PCB directly to the moulding (you can leave the brackets attached to the PCB).

For the Keytronic keyboard, remove the six screws fixing the PCB to the top moulding.

If these mean anything to anyone, page 96 (manual page 84) of the A5000 Welcome Guide lists the pin-outs as

Keyboard connector
The keyboard has a 6-way plug on the end of its cable, that goes into the 6-way socket on the back of the computer:
The pins on the socket are wired as follows:

• Reset
• No Connection
• 0v
• 5v
• Serial Data In
• Serial Data Out

Compared to the IBM PS/2 specification

• Data
• Not Connected (On some computers mouse data for splitter cable)
• Ground
• +5 V DC at 275 mA
• Clock
• Not Connected (On some computers mouse clock for splitter cable)

Here is the circuit diagram for anyone who is interested.

 Acorn_A5000TRM_keyboardCircuitDiagram.pdf (255.86 kB - downloaded 51 times.)