Dell Octoplex GX620 parallel port issues

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04 Aug 2019 23:58 #141376 by timko307
I've built a few hobby cnc machines using the Arduino/GRBL platform and they all perform great. I am working on a cnc Plasma table and as I expected, the Arduino is never going to cut it.
So I purchased a KL-DB25 6 axis breakout board from Automation Technology Inc, very similar to the DB25-1205 from Longs Motors and others.
I've installed Linuxcnc 2.7.14 on a Dell Octoplex GX620 and it seems to run fine. I'm able to load my gcode and it runs as expected with no BOB attached.
I've run stepconfig to set up the ports and pins for 3 axis motion and configured my drivers (TB-6600) to run my nema 23's.
The problem seems to be in the parallel port not able to send/receive. My stepper motors are getting power but will not turn any direction. I've tried multiple settings in stepconfig, tried on all 3 axis with no luck.
I got into the computer BIOS and changed the LPT Port mode to all available options, (OFF, AT, PS/2, EPP, ECP) and still not getting anything. (One thing I noticed in the BIOS the default LPT address is 378h, so I set my port address to the same with no change).
I connected my VOM to the port pins 2-7 and all of them read 4.4 volts whenever the computer is powered on. I have used the pyvcp Parport Test and it seems to be working, but when I toggle the pins the indicator changes from red to green, but the voltage remains at 4.4 volts.
I suspect the factory LPT port is faulty somehow and I'll have to get a PCI card installed.
I've spent the last 2 days in the forums and searching online for answers, but while I learned a lot I still have no clue to whats going on here.
I'm completely new to Linux OS and LCNC so it's very possible I've overlooked something simple in my setup. Can anybody shed some light on what I may be doing wrong here?
Many thanks.

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05 Aug 2019 01:53 #141388 by rodw
The very first question is do the steppers have holding torque or can you turn them by hand. Some of the controllers have an enable signal. IF power is connected , it disables the drive. so if you have connected those wires, unplug them.

If you have holding torque, you may have incorrect calibration and are moving super slowly.

There is a parallel port tester included with LInuxCNC. Maybe check it works. Pretty sure the DB-1205 is active low switching.

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06 Aug 2019 02:16 #141467 by timko307
Enable pins are not used and there is holding torque on the motors with power applied to drivers.
Calibration settings are correct for the motors and they do not move at all. No visible or audible indications that the motor is receiving pulses.
I have tried the parallel port tester. I thought that by toggling the pins (click on the pin number and the status light changes colors) that the output (LPT port on back of the computer) would change state, on/off? The lights on the tester do change from red to green, but the voltage measured on the corresponding pin remains 4.4 volts.
I really want to learn how to use Linuxcnc as I consider it a huge step up from Arduino as far as capabilities go.

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06 Aug 2019 05:38 #141477 by pl7i92
look into bios settings on the port
it shoudt be ECP or bidirectional to get the ports changing

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07 Aug 2019 23:34 #141639 by timko307
Okay, so I've reset the BIOS LPT port config to ECP.
I retested to voltage on the pins while jogging axis back n forth.
No change.
I know the system recognizes the port.

tim@Linuxcnc:~$ sudo cat /proc/ioports | grep parport
[sudo] password for tim:
0378-037a : parport0
tim@Linuxcnc:~$ ^C
tim@Linuxcnc:~$

How do I check to what driver is loaded? And what version should be loaded? And how would I load it if it's wrong / missing?
I'd rather not buy a PCI card if I can get this to work. It's just a bench setup for testing and learning Linuxcnc. If I can get it to work correctly, I'll likely invest in better computer, card and/or BOB from Mesa and go that way. But I want to know before if this is going to be right for me.

Thanks again.

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07 Aug 2019 23:39 #141640 by tommylight
Find a small LED light, put one pin on the output of the parallel port and the other on the metal shield of the parallel port, jog while looking directly at the LED. If it does not work, reverse the pins.
The port might be working but when there are slow steps the DVM can not measure is.
Also increase the jog speed to max, that vill make it easier to see/measure.

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07 Aug 2019 23:45 #141643 by Grotius
I don't use a dell pc for parport application's. No window's and no linux for ltp1 and dell.
Quicker is to grap another pc brand.

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07 Aug 2019 23:50 #141644 by tommylight
I use a LOT of Dell Optiplex computers on a lot of machines with parallel port or Mesa 5i25/6i25.
I do not think i ever used a 620. All of them are 7xx series.
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07 Aug 2019 23:53 - 07 Aug 2019 23:55 #141645 by Grotius
My favo is like the HP Compaq 6000 PRO. I tried a Dell once without succes. Maybe it is a sad story... :whistle:
Last edit: 07 Aug 2019 23:55 by Grotius.

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12 Aug 2019 21:12 #142003 by andypugh
It might be worth looking at a Mesa 5i25 or 6i25 instead of the parport. The form factor is the same as a PCI(e) parallel port, but with step generation done on-board the step rate and accuracy is orders of magnitude better. (no exaggeration, 20kHz v 10MHz max step rate)
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