I'd like a 'normal' USB keyboard that only has the up and down arrows. Preferably larger keys than normal. How easy to make one? My thoughts were to start with a normal keyboard for the electronics and make up a box with just the two press switches.
I reckon that is the easiest way...
If you choose carefully you should be able to find one where the arrow keys form a neat cluster and provided you are prepared to sacrifice the ^ and v keys could be made triple size fairly easily.
The MS keyboard I am using now has such a configuration. You couldn't do much about the full set on the numeric keypad though.
I'm happy to make up a little box with two generic push switches and just use the electronics from a keyboard. They're cheap enough, after all. But wondered if it really is as simple as this? I've never really looked at how they work. A circuit diagram of one would perhaps make it clear to me.
Depending on the layout it might be possible to hacksaw the majority of the keyboard away from the interface logic leaving a very small PCB for the essential bits.
Starting with a keyboard is way cheaper than buying the hardware to interface your own keys
You mean you have never spilt wine, tea or coffee over one and had to dismantle it for cleaning? Milk usually does for them as the rancid smell becomes intolerable after a while. Wine and black coffee are usually recoverable with a good wash and plenty of drying time.
The only thing I can think of is there might be a limit on the length of cable that you can run from the board to external device. And obviously you are stuck with rather large keyboard sized PCB.
A better choice might be to mechanically alter a compact dedicated numeric keypad sold for touch typists to use with laptops eg.
on 10/05/2012, Dave Plowman (News) supposed :
It is that simple - no circuit needed, just connect across the correct pads. The cheap modern keyboards are just a conductive rubber pad making contact across two PCB tracks.
I've done this where I wanted a headless system, but the BIOS on the system had no option to skip keyboard test, and I didn't want a keyboard. I took a keyboard, and sawed off the 1" square circuit board corner with the cable connection and IC under a blob of rubber. I put it in a potting box, and added a push button, which was connected across the keyboard grid at the F1 key position, giving me a tiny keyboard with just the F1 key, which the BIOS occasionally requires to skip past other errors at boot.
what no QWERTYUIOP at all?
sounds like a plan.
I've got a couple of MAC keyboards the cars pissed on you could pirate..
Alternatively its an arduino project.
Discovery Arm CortexM4 at £10 from RS is cheaper, but the learning curve to implement a HID keyboard from scratch would be very steep.
I ended up using the IAR development environment since it was the first one where the download of the toolkit actually worked as advertised!
It's just a matrix with a switch at each cross point. Most keyborads just have small board with the controller chip and USB or PS/2 interface. The hard bit is probably buzzing out which two points need to be connected for each key you want.
Option a) Get a normal keyboard, a couple of large keys, and set up a contrivance of wires, pulleys and hammers such that when the large keys are pressed, the hammers operate the up/down arrows on the regular keyboard.
Option b) Start with a normal keyboard for the electronics and make up a box with just the two press switches.
I'd go with option b... ;-)
Ages ago and I didn't pay much attention to how the switch contacts arrived back at the microprocessor.
The actual electronics are tiny. My idea was to incorporate them in the same box as the new keys, and just use the existing lead back to the PC.
I'd like slightly larger buttons - or spaced further apart.
I sort of guessed at something like that. A circuit diagram would make life easy. I'll have to do some serious Googling.
If its any use I have some flexible rubber keyboards such as at
Would another approach be to assign mouse keys to the up and down arrows while running the application in question? I can't give chapter and verse but ISTR I once had a Logitech mouse which had the option to assign in software any key to the mouse buttons.
Of course your standards are almost certainly higher than mine so a mouse glued to the dashboard may not suffice;)
They are usually arranged on a row/column matrix... often just printed on a PCB with conductive rubber pads on the back of the "switches" to short out the tracks...
So you should be able to stick a switch across one of the existing key positions on the PCB.
Err, why not get a friend to do it? Or better yet, get it to a rolling road and have someone else do it properly.
Do you know what rolling roads cost? And while they may be fine for quickly setting things for maximum power, getting it right for best economy at cruise is something else.
I'd also not tax a friendship by asking him to do something so boring. ;-)
Yep. Northampton Motorsport, where I go, charges £90/hr.
But if it took more than an hour, I'd be astonished.
If they're any good, they'll do whatever you ask. And driving whilst watching the lambda is almost certainly DWDCA. How many points do you intend to map, anyway? And where are you going to do it?
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