How do I control an LED message board via USB?

Hey, this is my first post so bere with me as I may be a bit all over the place.

I am trying to control an LED message board via usb.

It has a manual keyboard on the bottom that upon closer inspection has 8 wires on one side and 7 on the other.
By placing a wire between a wire on one side and a wire on the other a character is inputed.

So by using some sort of USB interface with at least 15 pins I think it must be possible to input to it via USB.

e.g. When A is pressed wires 8 and 15 should be connected in order to input A, for B wires 8 and 14 should be connected, ect.....

I am also getting my Rasberry Pi sonn and was thinking that the GPIO pins could do this but i'm not sure.


This website documents a similar project using the same display but via a different method: http://srimech.blogspot.co.uk/2003/04/led-message-board-hacking.html



Thanks for reading, please help!!!!

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A 'Pi would do it, if you attach a serially addressed analogue matrix switch to its GPIO pins. If you need some part suggestions, just shout.

Steve
jacobknott (author)  steveastrouk5 years ago
Thats sound best as plan on showing current user numbers of a website and using a Pi means I can leave it running without sacrificing a laptop.

How would I go about this?

Thanks
Take a look at something like the MAX4587, which is a 4:1 mux switch - you'll need 14 of 'em !

Or. the ADG728 - you'd need 7 of them.

I hesitate to suggest the DG884, of which you would only need two, because they are parallel addressed, and I don't know how many external GPIO pads the PI exposes.

jacobknott (author)  steveastrouk5 years ago
Thanks,

I here is the layout of the raspberry pi's gpio pins http://elinux.org/images/2/2a/GPIOs.png


I was also wondering if arduino uno would be capable of this?
It HAS SPI out on there - which makes this MUCH easier to go for the first two parts I suggested.
iceng5 years ago
Sounds like a USB micro processor whose output lines controls a small matrix of mosfet LED 6 pin IC opto isolators.

Parallax inc sells a USB stick uP with a patch area and simple free software that could do this for you.

A