RS232 keypad

[Roger Bagnall]

Hi,

Can anyone help me with a link or circuit for the following:
I am wanting to build a small cabled remote control keypad with 2 or 3
buttons to control a PC during powerpoint presentations without having to
have the mouse or keyboard on the lectern. I have seen these before but the
only types i can find on the web are IR types.
Ideally i would like it to use the RS232 port or parrallel port. Has anyone
seen such a device and the software for it, i doubt it would be too hard to
build ?

Thanks in advance.
RB
[email protected]

 

[Marco]

Hi,

Can anyone help me with a link or circuit for the following:
I am wanting to build a small cabled remote control keypad with 2 or 3
buttons to control a PC during powerpoint presentations without having to
have the mouse or keyboard on the lectern. I have seen these before but the
only types i can find on the web are IR types.
Ideally i would like it to use the RS232 port or parrallel port. Has anyone
seen such a device and the software for it, i doubt it would be too hard to
build ?

Thanks in advance.
RB
[email protected]

A long time ago (1997) I worked at a computer resellers. Whe had
cordless mice that didn't need any surface. Just move your wrist aand
the mousepointer reacts. Maybe a bit overdone here, but they where quite
cheap and the buttons will work I guess

Marco

 

[Mike Page]

Hi,

Can anyone help me with a link or circuit for the following:
I am wanting to build a small cabled remote control keypad with 2 or 3
buttons to control a PC during powerpoint presentations without having to
have the mouse or keyboard on the lectern. I have seen these before but the
only types i can find on the web are IR types.
Ideally i would like it to use the RS232 port or parrallel port. Has anyone
seen such a device and the software for it, i doubt it would be too hard to
build ?

Thanks in advance.
RB
[email protected]

My Saitek gamepad (USB) comes with software to enable it to press
buttons in whatever Windows app you're running. That doesn't scan very
well. I mean, when you hit button 1, you can have the software press 'Q'
or space or whatever you program. You just need to find a small one.

 

[Ken Taylor]

Hi,

Can anyone help me with a link or circuit for the following:
I am wanting to build a small cabled remote control keypad with 2 or 3
buttons to control a PC during powerpoint presentations without having to
have the mouse or keyboard on the lectern. I have seen these before but the
only types i can find on the web are IR types.
Ideally i would like it to use the RS232 port or parrallel port. Has anyone
seen such a device and the software for it, i doubt it would be too hard to
build ?

Thanks in advance.
RB
[email protected]

Why do you assume it's easy when you don't know how to do it? The hardware
may be easy enough but what software are you going to use? <End Rant>

Try:
http://www.hagstromelectronics.com/modules.html
http://store.yahoo.com/membrane-switches/pckeyen.html
http://www.audon.co.uk/keyboard_encoders.html

They come with software too I think.

If you want to build from a decoder IC and just put in whatever limited
number of keys you want, try:
http://www.holtek.com.tw/docum/computer/82k28a.htm

Cheers.

Ken

 

[Roger Bagnall]

I presumed that creating the circuit would be easy, as far as i can see i
just need some buttons which can be connected directly to the correct wires
of the RS232 port so that the PC would register a signal when the button is
pressed. Unfortunately my first problem is that I do no know which wires
would need to be connected where.
The second problem is, of course, the software side - I hoped there would be
software available which could recognise the incoming signal and do
something with it.
My knowledge of electronics is not that great (am actually a biological
scientist), which is why i posted here where there would be experts on these
matters.
I would also prefer to build as oppose to buy something as i will need 5 and
the only type i can get in this country cost R250 each for an IR type, which
is going to be too expensive for a twice only use. (Thus gamepads and
cordless mice are also out as they are even more expensive).

Thanks for all the info so far.
rb.

 

[Peter Nolan]

Hello Roger,

I was looking for just this device to signal a HP Jornada 545 PocketPc.
Writing the code in Visual Basic(eMbedded VB 3.0 for the PocketPC) is easy
and I can send and detect simple strings between the PC and PocketPc using
their RS232 ports. The problem, of course is getting up to speed with VB and
this doesn't happen overnight.
I was wondering if there are RS232 keyboards out there. I tried to find one
in Google but couldn't.
www.farnell.com supply Universal Keypad+Keyboard Encoder stock number
177-687 but is very expensive at say around $100. I have their 2000
catalogue. It says no assembly or programming required but I don't get this.
I just checked the Farnell website so enter the above stock number and you
can get to the datasheet.
I'm very surprised there is nothing out there off the shelf.
Farnell have good technical support and I guess you can email them to find
out more.

Peter Nolan.
Dublin.

 

[j.b. miller]

There isn't a big market for RS232 keyboards. I had to make up replacement
units for a friend of mine.
I ended up using a regular PS2 keyboard and designed a 'convertor' to output
ASCII RS232 with appropriate translation table for his special needs. ONCE I
got the basics worked out,it was a piece of cake. Hardware cost about
$50,then it was just programming time.
Commercial units do exist for big bucks, but for what you need (2-3 buttons

RS232) , an easier $50 solution would work. Either find a local

electronics kid to help,try a tech school with electronics or....hire me!

hth
jay
hmm... just thought of a simpler solution,NO hardware needed(OK, 2 or 3
switches). Use the RS232 'status' bits like DTR,RI and poll them.Man ,
that's way too simple.

 

[Roger Bagnall]

Hi Jay,

This sounds exactly what i was thinking (with my lack of electronics
knowledge) and then using some software like PC Remote Control to modify the
signal to a keypress ??
Thus the cable would be an standard D connector to the PC com port and end
basically in open wires, with 2 microswitches to close a circuit ? Once a
key is pressed the circuit would be completed, the com port and software
would register (a keypad keypress) and then the software would send the
(mouse click) command to the presentation software ?
I have used PC Remote Control software before with an IR receiver system i
built and it worked quite well, but IR that system was too complex and
expensive for the current purpose.

Could you tell me what wires need to be connected where ? Would you mind
giving me that info without me hiring you ? (will send you a thank-you
e-card)
(the only thing that worries me now is, what is someone presses and holds
the button ? Would there be a way to let it register only 1 keypress even if
the button is held down) but i guess that last bit is not really serious,
just me being finicky.

Thanks greatly for the help
rb.

 

[Matteo Gamboz]

Hi Jay,

This sounds exactly what i was thinking (with my lack of electronics
knowledge) and then using some software like PC Remote Control to modify the
signal to a keypress ??
Thus the cable would be an standard D connector to the PC com port and end
basically in open wires, with 2 microswitches to close a circuit ? Once a
key is pressed the circuit would be completed, the com port and software
would register (a keypad keypress) and then the software would send the
(mouse click) command to the presentation software ?
I have used PC Remote Control software before with an IR receiver system i
built and it worked quite well, but IR that system was too complex and
expensive for the current purpose.

Could you tell me what wires need to be connected where ? Would you mind
giving me that info without me hiring you ? (will send you a thank-you
e-card)
(the only thing that worries me now is, what is someone presses and holds
the button ? Would there be a way to let it register only 1 keypress even if
the button is held down) but i guess that last bit is not really serious,
just me being finicky.

Thanks greatly for the help
rb.

try this for some serial port specs:
http://www.lammertbies.nl/comm/info/RS-232_specs.html

 

[Howard Henry Schlunder]

Could you tell me what wires need to be connected where ? Would you mind
giving me that info without me hiring you ? (will send you a thank-you
e-card)
(the only thing that worries me now is, what is someone presses and holds
the button ? Would there be a way to let it register only 1 keypress even if
the button is held down) but i guess that last bit is not really serious,
just me being finicky.

In terms of hardware, all you need is this: [ http://www.public.asu.edu/~hschlun/SerialButtons.png ]. The buttons are normally open momentary contact switches. To make it work, the computer must set the DTR pin to a different value from the RTS line. In other words, I would recommend setting DTR to 1 (True) and RTS to 0 (False). When a button is pressed the corresponding input line will turn to the value of DTR (True).

In Windows, you can detect the line changing state by calling the WaitComEvent and subsequently calling the GetCommModemStatus API function when WaitComEvent returns. If you are using Visual Basic (ver 6.0 prefered), controlling the COM port is trivial with the Microsoft Comm Control 6.0. Sending a mouse click is as easy as calling the SendInput or the mouse_event API function. If your "PC Remote Control" can't handle it and you don't know how to program, now is an excellent time to learn how.

Howard Henry Schlunder