Simple keyboard/dry-contact to RS-232 converter?

[Gary Sanders N8EMR]

In article <3lao5t$5...@crcnis3.unl.edu> cra...@herbie.unl.edu (Chris Radek) writes:
>Does anyone know of a simple way to do either or both of the following two
>things:
>
> 1) Scan a matrix-wired (row/column) keypad and transmit the results
>to an RS-232 port, and
>
> 2) Read a series of dry contact closures and transmit the results
>the same way?

Paralax has a number of contacts to RS232 interfaces available. They
also have contacts to PC keyboard interface.

I dont have there address or phone handy at work, but they do advertise
quite a bit in circuit cellar. If you cant find it email me.

--
Gary W. Sanders g...@n8emr.cmhnet.org
packet: N8EMR @ W8CQK Voice: 614-895-2552 (eves/weekends)
Always remember you're unique, just like everyone else!

[Chris Radek]

Does anyone know of a simple way to do either or both of the following two
things:

1) Scan a matrix-wired (row/column) keypad and transmit the results
to an RS-232 port, and

2) Read a series of dry contact closures and transmit the results
the same way?

The primary difference between these two things is just that the second one
would use one bit per switch, whereas the first would need some kind of
keyboard encoder built-in. I know of many ways to do this, but most are
either expensive, overly complicated, or both. By the time you build
something with a UART, some keyboard encoding, serial line drivers, etc, it
gets a bit messy. I've been hoping to come up with something commercially
available that's relatively cheap, which could be taken apart and used for
this purpose. I believe I've seen add-on numeric keypads for laptops
without a keyboard connector which attach to the serial port and use a
driver to stuff the keyboard buffer, but I haven't been able to locate any
now that I want one (or six). Does anyone know of any other cheap (under
$30 or so) consumer-type computer peripheral that would take care of this?
If I can't find anything, I suppose I can put together 5 or 6 PIC boards to
do it without too much trouble, but I'd rather spend my time working on the
real project (home automation) instead of building PIC's. Any help?

[Chris Radek]

Hmm... I've seen Parallax's ads in Circuit Cellar for the "Basic Stamps" and
PIC programmers, but I didn't realize they made anything else. I'll have to
investigate that. Thanks!

[Barry L. Lankford]

In article <1995Mar29.1...@n8emr.cmhnet.org>

g...@n8emr.cmhnet.org (Gary Sanders N8EMR ) writes:

>In article <3lao5t$5...@crcnis3.unl.edu> cra...@herbie.unl.edu (Chris Radek)
>writes:

>>Does anyone know of a simple way to do either or both of the following two
>>things:
>>
>> 1) Scan a matrix-wired (row/column) keypad and transmit the results
>>to an RS-232 port, and
>>
>> 2) Read a series of dry contact closures and transmit the results
>>the same way?

>Paralax has a number of contacts to RS232 interfaces available. They

>also have contacts to PC keyboard interface.

>I dont have there address or phone handy at work, but they do advertise
>quite a bit in circuit cellar. If you cant find it email me.

>Gary W. Sanders g...@n8emr.cmhnet.org

>packet: N8EMR @ W8CQK Voice: 614-895-2552 (eves/weekends)
>Always remember you're unique, just like everyone else!

You might be interested to know that Parallax has a WWW page. It is at:

http://www.parallaxinc.com/

Barry L. Lankford email: bar...@nuance.com Amateur Radio: N4MSJ
Madison, Alabama, USA ICBM: 34deg 41min 52.2sec N, 86deg 45min 34.2sec W

[Don Pomplun]

depending on how big a matrix you want to deal with, you can always
program a basic stamp to read contacts and transmit serial data. would be
easy!

[Jim Barron]

If you mean a circuit you could incorporate into a design, you could use a
74C922 (National Semi?) which I have used, with a UART.

The 74C922 requires a couple of capacitors but is fairly easy to use; it
creates a strobe signal and a hex digit output for whatever button is
pushed on a 4 x 4 pushbutton matrix.