Hacking an old laptop keyboard

[electroniks]

Hi everyone,

I recently cracked open my 10 year old laptop and took out the keyboard. The model number is WLJ-5538W from an old toshiba laptop.

It has a 34 pin ribbon cable attached to it with 4 pins not connected. Is there a way to use this keyboard like a normal keyboard?

I tried doing a simple connectivity test between a few pins but failed. How would you get any key presses from this thing?

 

[Ian Rogers]

Normal PC keyboards only have 102 or so keys... A laptop has much less... The smallest network for 102 keys is 17 x 6

In other words 23 pins.... So it would take a long while to match the pins...

Answering your question! Yes you can use the keyboard for other stuff.. Open it up and trace the network underneath..

 

[electroniks]

I was hoping there was a standard to work with or maybe someone could tell me how to map the pins... does a connectivity test between pins work or it needs a voltage?

 

[Ian Rogers]

If you can get hold of a schematic from toshiba it would make it easier..

 

[electroniks]

How about a circuit that does the job? Maybe a few 8 bit OR gates and a bunch of LEDs to test which buttons I am pressing?

 

[Dr_Doggy]

A logic probe ( led, resistor, batteries in series with 2 wires ) can tell you what you want to know , providing there is no IC chip in the keyboard, may not have same success with touch pad if that is on the ribbon too,

keyboards use a matrix to encode, so going by ians example , if we have 17x6 pins, then when you apply power to one of the 17 pins, and press a key you will get volts(led will light) on one of the 6 "outputs"
so your key map will look something like this:

g= (11,1)
h=(11,2)
i=(12,1)
j=(12,2)

this is just an example...

 

[Les Jones]

Here is a suggestion. Plug it back into the laptop and with NO KEYS pressed look for pins that have pulses on them. All of these will be on one axis. So if it follows the layout that Dr_Doggy thinks it will be you will find either 6 or 17 pins with pulses on them. Onece you have this information it will be easier to sort out the key layout using a meter.

Les.

 

[Ian Rogers]

This is from a satellite:-

Notice

 

[michael8]

Normal PC keyboards only have 102 or so keys... A laptop has much less... The smallest network for 102 keys is 17 x 6 In other words 23 pins.... So it would take a long while to match the pins...

What about 7 x 15 for 22 pins or 9 x 12 for 21 wires?

 

[Dr_Doggy]

really it just follows the manufacture's compatibility specs. and how they built their matrix, those numbers were just examples, datasheets reveal all

 

[large_ghostman]

Many laptop keyboards dont have the decode chip on the keyboard its on the mobo, I would use a micro to convert the signal to ps2 if you have a ps2 socket that is, there is code kicking around for pics and ps2 and also USB I think