Build a single button?

[Synomenon]

Anyone know how to build a single button that connects to a PS/2 keyboard port and simulates / acts only as the letter "z" on a standard PS/2 keyboard?

 

[C1]

You could have this company, Genovation, custom build such a device for you (or maybe just the circuit card & you add the case, button and PS2 cabling).

http://www.genovation.com/custom.htm

 

[Ben90]

If you know how to wire your own circuit boards this will probably be all the information you need:
http://www.computer-engineering.org/ps2keyboard/

Another option would be to take the controller out of a standard keyboard and figure out which traces need to be connected for the desired button operation. It would be kinda a pain in the ass, but less work that building your own controller.

A third option would be a company like mentioned above build your own controller.

 

[Cogman]

Not a really an easy thing to do. http://www.burtonsys.com/ps2_chapweske.htm

PS2 works on serial connections, to make a z only key will require a microcontroller to send programmed to send a z sequence whenever one of the input of the inputs go hi (or low, depending on how you role)

 

[C1]

There are people who do this every day. It would involve use of a PROM and driver chips put together on a custom circuit board. If you want a slick compact integrated design then you will need to subcontract this job out if you dont have the skills already to do it unless, of course, you're the "birdman of Anandtech".

 

[Synomenon]

Doesn't have to be fancy. I'll I'd need (besides the programming skills which I don't have) is a small project box, the circuit board and ROM chip, a momentary switch and the PS/2 connector / cabling.

 

[PottedMeat]

Another option would be to take the controller out of a standard keyboard and figure out which traces need to be connected for the desired button operation. It would be kinda a pain in the ass, but less work that building your own controller.

This is what I'd do. Find junk keyboard, note where 'z' key is, disassemble, find relevant traces, disconnect ribbon cable, test with momentary switch.

 

[Daedalus685]

The how is all well and good.. I'm more interested in the why though 😀.


That being said, the actual electronics of a keyboard is nearly nil these days. The buttons themselves take up all the space and are just leads that trace to the controller which is in most keyboards no larger than. You can simply trace out the z key and carefully disassemble around it leaving quite small bits behind on any old junker far easier than you could make your own. You'd end up with a card about the size of 5 or 6 keys and provided you were careful to note the z leads any old switch will work.

 

[William Gaatjes]

A simple mcu like the 16f675 would be sufficient. But you have to program it in pic assembler(software is free available at www.microchip.com).

Another option might be to use the ic that comes with the TI launchpad.
Then you have a free compiler(Look at the the TI launchpad thread here in HT).
It will cost you 4.30 dollars and you will be able to program it in C.

Together with the information on this page from ben90 :
http://www.computer-engineering.org/ps2keyboard/

Send scan code of z key pressed and afterwards send scan code of z key released.

And you are ready to go.

Perhaps Modelworks and Cyclowizard have some ready set software examples for you...
It never hurts to ask...
Maybe even an USB example is possible.

Here is the link to the thread :
http://forums.anandtech.com/showthread.php?t=2087844

 

[Modelworks]

It is very easy to interface a ps/2 keyboard with a micro, they only need 2 pins for communication, data and clock. It gets a bit more complicated when you want to make a micro look like a keyboard to the host.

Follow the links given in the post above for the proper codes to send and you basically will have to send those to the host pc to even get it to accept the micro as a keyboard before you can begin sending it actual keys.

Here is a rundown of how to do it with a pic :
http://www.piclist.com/techref/microchip/picboardasm.htm

To get the codes for your specific pc then you are going to need to sniff the traffic. The easiest and cheapest way to do this is with a buspirate. It can use a ps2 keyboard out of the box and decode the data being sent on the lines.
http://dangerousprototypes.com/docs/Bus_Pirate

 

[Synomenon]

Thanks for all the reference material guys. Now I just need to find someone that knows what to do with all of it.

I'm not a programmer and I don't know how to work with circuit boards.

 

[Synomenon]

I think I found an easier way to do this. A general guide (won't follow it to the letter, but it gives a general idea of what to do):
http://www.instructables.com/id/USB-Easy-Button/

This is what I'll need:
Uhid Nano
http://www.u-hid.com/home/uhid_nano.php

Project Box
http://www.performance-pcs.com/catal...x&cPath=60_610

Momentary Switch
http://www.performance-pcs.com/catal...ducts_id=23257

+
miscellaneous wires.

Anyone think this will work?

 

[ModestGamer]

Pic has alot of small device application support. I'd bet somebody already has sample code that could easily tweak for the application if not a key mapping to I/O utility with ps2 port com library already built in. You could use a custom key mapping application "there are a few" and put the request in over serial port even easier.RS 232 is stupid easy.

A simple mcu like the 16f675 would be sufficient. But you have to program it in pic assembler(software is free available at www.microchip.com).

Another option might be to use the ic that comes with the TI launchpad.
Then you have a free compiler(Look at the the TI launchpad thread here in HT).
It will cost you 4.30 dollars and you will be able to program it in C.

Together with the information on this page from ben90 :
http://www.computer-engineering.org/ps2keyboard/

Send scan code of z key pressed and afterwards send scan code of z key released.

And you are ready to go.

Perhaps Modelworks and Cyclowizard have some ready set software examples for you...
It never hurts to ask...
Maybe even an USB example is possible.

Here is the link to the thread :
http://forums.anandtech.com/showthread.php?t=2087844