View Full Version : Problems with parallel port

09-07-2007, 06:44 PM
I split my board in 3 parts, one for each axis. I get a very faulty signal from ports 2 and 3 (step / dir) and 4 and 5 of the parallel port. Signals from 6 & 7 run my steppers perfectly. I switched the boards around just for the sake of testing the boards and I got the same faulty signal on boards that worked OK in ports 6 & 7.

I also checked the cable and it was OK.

Can this be fixed , is there a way to get around this or do I need to get another PC?

What would I need to check what is going on? I only have a digital multimeter.


10-06-2007, 10:19 PM
I would look into buying a parallel port card. It may be the port or it may be something else. What software are you using? What OS are you using? This can make a difference as well. Not sure about the issue of switching the cards and still having the same problem, though. That would be the cheap and easy place to start.

10-07-2007, 12:02 AM
I am running CNCpro with Windows 98. Most likely I blame it on the cable. I am trying to make one, but it is a pain to solder a 25 pin cable.

Thanks for the help.

10-07-2007, 07:06 PM
Could be incorrect termination at the board end. Parallel ports need to be terminated correctly.

10-08-2007, 07:40 AM
also, cncpro requires true dos. are you running in a dos window or booting directly into dos.

10-08-2007, 09:13 AM
I usually restart the computer in DOS mode.

10-08-2007, 10:00 PM
let us see closer to the Lpt port first, you can always use just a resistor (330 Ohm) + a led to see what's the output of any pin of the port.

pin (0..7) ---- Resistor (330 ohm) ----- Led ------ pin (18..25)

pin 18..25 are all ground

by this way you can see if the output is ok on every pin (0..7) of the port
send 255 to the port and see.