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Author Topic: How to test a parallel port.  (Read 29543 times)

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How to test a parallel port.
« on: February 27, 2008, 10:43:47 PM »
I`d like to test my two parallel ports to see if their working correctly.
What`s the best method for this type of test.

Offline Tweakie.CNC

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Re: How to test a parallel port.
« Reply #1 on: February 28, 2008, 03:53:58 AM »

I came across this a while ago, it may be of use to you. They charge for the full version of the software but a free, limited version is available to download and try from their website.


Good luck,


Offline stirling

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Re: How to test a parallel port.
« Reply #2 on: February 28, 2008, 04:52:46 AM »
Hi Barry - you haven't actually said what type of test you're wanting to do but here's a couple of example tests you can do with just Mach.

Short an input pin of port 1 to gnd and you should see the result on the diagnostics screen (Port 1 pins current state)
You can check port 2 by using the  getPortByte function call in a script. Similarly you can write to the ports outputs with putPortByte.



Offline jimpinder

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Re: How to test a parallel port.
« Reply #3 on: February 28, 2008, 11:01:38 AM »
You can test both your parallel ports quite simply, with a volt meter. You will  have to make some sort of lead out to a piece of printed circuit board (rather like a DIY breakout board). I used an old printer cable and a piece of printed circuit card. I identified all the pins on the 25 pin plug, and soldered them in order onto the card.

Testing the port after that, is childs play.
The printer port - LPT1 has the following sets of pins.  OUT  pin2 to pin9.  OUT pin 1,14,16,17 and IN pin 10 - 13, 15. Pins 18 to 25 are signal return (computer gnd) wires.

All the output pins can be tested by allocating each pin to output 1 on Config/Port and Pins/Output signals.  If you then go to Spindle set up and allocate M3 to Output 1 and untick disable spindle relays,  if you click "spindle" for example on Mach3 Turn, the output on the slected pin should change from 0v to 5v, or 5v to 0v depending how you have set "active low". You can use this, or type M3 into the GCode input - which will turn the output on, or M5 which will turn it off.  Since you can allocate any pin to Output1 you can test all the outputs.

Similarly with the inputs - allocate them to a "limit switch or home switch". If as has been said, you then short the input to ground, you should see the appropriate LED change.

You can test you second port in a similar way, but I assume you can allocate the pins to be inputs or outputs, so it is up to you how you test it
« Last Edit: February 28, 2008, 11:06:13 AM by jimpinder »
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