Re: Building an input device to send a specific keystroke (or set of keystrokes) to a computer
- From: Michael Black <et472@xxxxxx>
- Date: Wed, 21 May 2008 20:11:30 -0400
On Wed, 21 May 2008, Stephen J. Rush wrote:
On Wed, 21 May 2008 09:08:13 -0700, fny1182 wrote:I don't know what it's like with USB keyboards (I've never had one, so I
I want to build a device (ideally USB) that functions as a keyboard, to
an extent. I don't want it to have all the keys however. There is a
particular application that requires only a single key: scroll lock. I
want to set it up as a sort of hand-held clicker.
Long story short, this is designed to interface with a time keeping
program. When someone crosses the finish line, the timekeeper currently
holds Function-Scroll Lock which gets kind of annoying. I had envisioned
something a little better for the poor guy, basically a push button that
connects to the computer and sends the scroll lock code to the computer
via USB.
Hacking the keyboard is the simplest approach, just a SPST switch and
some cable. If you don't want to hack into the computer, Micro Chip and
Atmel make microcontrollers that include USB interfaces. This may look
like massive overkill for one key, but some of these chips are absurdly
inexpensive.
can't look inside) but at least some PS/2 keyboards I've opened have a nice small circuit board, separate from the matrix board for the actual keys. Those then make it really easy to make a custom keyboard or
whatever, since it's really easy to extract the small board.
Of course, in the old days, this sort of thing would most easily be
done with the use of a parallel input board, or even one of the control
lines on a serial board. It does require adapting software to look
for the keypress on the serial or parallel board, and these days it
seems like serial interfaces are not standard in computers, maybe not
even parallel printer ports these days.
If the software can be modified, the most easily accesible thing
nowadays may be the mouse, in effect a USB interface that can take
a number of on/off inputs.
Michael
.
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