Good day
My name is mike and I recently found an old lap top.
It's an AST Premium Exec 386SX/20.
I could not get it to work so have decided to turn it into a Raspberry pi lap top.
I will use a 7"touch screen and the original key board.
The question I have is... How do you integrate the old keyboard. I was thinking of using an old controller from a usb keyboard and I'm not winning.
Please help.
Regards
Mike from South Africa.
NerdJHB:
Good dayMy name is mike and I recently found an old lap top.
It's an AST Premium Exec 386SX/20.I could not get it to work so have decided to turn it into a Raspberry pi lap top.
I will use a 7"touch screen and the original key board.
The question I have is... How do you integrate the old keyboard. I was thinking of using an old controller from a usb keyboard and I'm not winning.
Please help.
Regards
Mike from South Africa.
What I would do is see how the keyboard is interfaced to the motherboard; likely it is some kind of ribbon cable; note the position of the cable, and carefully remove it from the connector on the motherboard (you may have to unlock the connector by sliding a tab or two on the sides/top of the connector - be very careful as you remove the ribbon cable, as some are thin and prone to tearing - also, don't flex it around too much).
Once you have it off the motherboard, disassemble the rest of the laptop - but keep the motherboard.
Take a look at the connector and the motherboard area around the connector. Sometimes, this is best with a lighted magnification lamp, or even better - one of those USB microscopes if you have one. Check out where the PCB traces go. Check and see if any are on the opposite side of the motherboard. Count the number of traces on the ribbon cable, and try to match that up to the traces on the motherboard. You might also try scanning the motherboard on a flatbed scanner, then use a paint program to flood fill traces to figure out where they go (old trick of the reverse-engineering trade).
Once you have all of that down and documented (as best as you can) - then use a dremel or other hobby tool to cut out the PCB around the keyboard connector. Try to locate and preserve any bare test-points or thru-holes that look like they go to the traces of the connector. Solder wires to those points (the wire might have to be fairly thin - an old floppy drive cable would work ok, likely); for those traces which have no test points or such, carefully scrape away (using an xacto knife) the coating over the trace to expose the copper, and solder to that. Apply hot glue liberally to the connections (strain relief).
Now comes the hard part. The keyboard is likely some kind of grid or matrixed system (like a telephone or alarm keypad - only a bit more complex). You need to identify which wires are "common" - which run to rows and which run to columns, etc. Use a multi-tester set for resistance or continuity reading for this, and take your time, make lots of notes. If you have other tools (or can improvise tools) to help track down how things are connect, by all means, use them. Also - be sure to look up any serial or model numbers on the keyboard (you never know what you might find out there).
Once you know what the matrix is, then it's a matter of hooking the keyboard up to an Arduino (perhaps a leonardo?) and writing a USB keyboard emulator - which can then plug into the Pi. I mentioned the Leonardo because it has a built USB:
https://www.arduino.cc/en/Main/ArduinoBoardLeonardo
...which makes it ideal for these keyboard and mouse emulation tasks.
Although the Leo is discontinued. 
