Re: Connecting a Linux box to a Soda Machine
From: Michael Black (et472_at_FreeNet.Carleton.CA)
Date: 03/17/04
- Next message: Popeye 'Bailo' Doyle: "Re: Recommendations for a Linux System"
- Previous message: General Schvantzkoph: "Re: Recommendations for a Linux System"
- In reply to: Matthias: "Connecting a Linux box to a Soda Machine"
- Next in thread: Matthias: "Re: Connecting a Linux box to a Soda Machine"
- Reply: Matthias: "Re: Connecting a Linux box to a Soda Machine"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Date: 17 Mar 2004 19:50:44 GMT
Matthias (thias@ecst.csuchico.edu) writes:
> i'm working on a project to connect a Slackware box to a Soda Machine.
> The idea is to use a some sensors in the soda machine to simulate
> keypresses on a dumb terminal keyboard. The input would be run through
> one of the two 25pin inputs on the top of the keyboard and then to the
> actual.
>
> The problem is that the keyboard has an RJ11-ish (it is slightly
> smaller than a regular phone jack) connection. QUESTION: how do i
> attach a RJ11 to a DB9 serial port on my box?
>
But aren't you assuming too much? Once upon a time, keyboards that output
ASCII were pretty common, with a parallel output. I suppose there was
even a time when you could find ASCII terminals with RS-232 serial output.
But I don't think that has been the case for many years. There is much
more likelihood that any keyboard you come across outputs some odd code,
or at the very least non-ASCII; afterall, the two common home/office
computers, Apple and IBM compatibles, do not output ASCII and they are
not RS-232 compatible.
If the keyboard uses a phone jack, likely that's because it's a small
connector, and the keyboard is intended to be used with the actual terminal,
which takes care of making sure the terminal outputs ASCII at RS-232 levels.
ON second reading, it sounds like you are taking an old idea and trying
to make it work, without the needed equipment.
At the very least, you should be offering some details (make and model)
of the keyboard have at hand, in case someone can recognize it and tell
you if it's useable.
But you can also rethink the scenario.
Put a computer right at the coke machine, and then use a normal keyboard.
Wire the sensors across the keys. If you are lucky, you will be able
to find a keyboard that has the encoder separate from the keys, and you
can just extract and use that.
If you need sufficiently few sensors, then you might be able to use
the parallel port to input those sensors (as in less than eight). Then
you just feed the switches into the parallel port that has been set up
for input. Maybe you'll need some schmitt triggers to get rid of noise
on the switches.
The point of a serial keyboard is that one can run longer lengths of
cable to the actual computer. So dig up or make an ASCII encoder,
and use that for encoding the switches into serial ASCII. Such ICs
were once common, are likely now harder to find. You can make them
from simple CMOS ICs.
Realistically, you don't even need to generate the full ASCII alphabet,
since you will only have a handful of sensors. So you could dig up
a UART (again they used to be common, but finding one that is not
intended for use with a CPU bus may be more difficult), and then use
the sensors directly as the eight inputs to the UART. No encoding needed,
because you'd know that ASCII 00000001 is "the machine is empty" and
ASCII 11111111 is "the machine is full" since that's where you hooked
up the sensors. Some sort of encoder, for this application, is only
needed if you need more than 8 sensors.
I suspect the way to do it today, so long as you want the coke machine
remote from the computer, is ethernet. I gather you can get little ethernet
modules for this sort of thing, though I've not paid attention.
Micahel
> i found this:
> http://www.airborn.com.au/rs232.html
>
> Which almost implies that i can just loop back some of the wires to
> make handshaking work. But the question is still around: what wires on
> the RS11 are Ground, Tx, other(???).
>
> Does anyone have an idea how to make this connection? I can't seem to
> find a terminal for my dumb term. If i could, it would simply be a
> matter of attaching the Female DB9 on the back of the screen to the
> Male DB9 on my box.
>
> thanks
> --Matthias
- Next message: Popeye 'Bailo' Doyle: "Re: Recommendations for a Linux System"
- Previous message: General Schvantzkoph: "Re: Recommendations for a Linux System"
- In reply to: Matthias: "Connecting a Linux box to a Soda Machine"
- Next in thread: Matthias: "Re: Connecting a Linux box to a Soda Machine"
- Reply: Matthias: "Re: Connecting a Linux box to a Soda Machine"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Relevant Pages
|
