Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Borisw37 on March 20, 2013, 02:52:10 PM

Title: Parallel Port output pins ?
Post by: Borisw37 on March 20, 2013, 02:52:10 PM

I'm in the process of making wiring up my 3axis CNC machine and trying to figure out which pins are suitable for output. I have found plenty of data online (http://www.lammertbies.nl/comm/cable/parallel.html) but not everything is matching up.
I need 6 outputs for the motors and another 4-5 for additional functions. Problem is that when connected to the PC, the following pins on the DB25 all ring out to GND (14,16-25). According to the info I found, pins 14,16,17 should be outputs.
Am I doing something wrong?

Title: Re: Parallel Port output pins ?
Post by: Chaoticone on March 20, 2013, 03:11:56 PM

The cable needs to be a straight thru cable.  I think most printer cables are not.  Second guees would be, possibly those pins have pull down resistors in the circuit some where.

Brett

Title: Re: Parallel Port output pins ?
Post by: Borisw37 on March 20, 2013, 03:19:52 PM

Cable is straight through, I checked it pin-to-pin before connecting it to the PC. Its a parallel port printer so DB25 to 36pin, but the pin out matches one in the link above.

Title: Re: Parallel Port output pins ?
Post by: Tweakie.CNC on March 21, 2013, 06:03:20 AM

Hi Boris,

I think you need the wiring diagram of the breakout board you are using to establish the correct connections.
Obviously there must be exceptions with a 36 pin Centronics connector but all the breakout boards I have ever used have a DB25 connector so the PC to Machine LPT cable is straight through connections DB25 to DB25.

Tweakie.