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Eavesdropping on a parallel printer

 
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Before anyone gets worried, this is nothing nefarious or illegal. I have a parallel line connected to a printer. I only have access to the printer end of the line and not the source. What I want to do is write an application to intercept this data and use it to drive programmable LED message boards. I want to leave the printer unaffected so that the data prints both to the printer and the LED message boards.

Does anyone know of a relatively inexpensive way to split off the parallel signal and send it to both the printer and another computer simultaneously? Since I don't have access to the computer originating the printer traffic, the solution can't be anything which requires me doing anything to that computer, nor do I want to do anything which would affect the functioning of that computer or the printer.

I'm operating under the assumption that once I split that line off, I will have to use a parallel-to-serial converter and read the intercepted data off of the eavesdropping computer's serial port.

Does anyone have any ideas how I might go about approaching this problem?
 
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I have not used / seen one of these things in over a decade, so I don't know if you can still get them... but basically, what you need is a breakout box. (and an understanding of the signalling on the parallel port)

I would suggest googling "breakout box", and "parallel port".

Henry
 
Jason Menard
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Thanks for the suggestion, Henry. I'll look into that.
 
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