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Hello,

If you do not have a scope you can use a voltmeter on the direction pins of the parallel port , moving one direction should be around 5 volt the other direction 0 volt.

Rick G

jblain wrote:I thought I had spotted the problem until I checked the HAL…
Incidentally, you can turn the reset back on for your step pins, it should double your step rate.It is unlikely to be that (very unlikely) though some ports can sink more current in EPP.You should be able to test the dir pins with a multimeter.
Jog one way, then try to jog the other, watching the voltage at the drive.
Then try the same test with the pins disconnected from the drive. (don't make/break connections to the drive while it is powered up)

You can take almost everything else out of the puzzle with: wiki.linuxcnc.org/cgi-bin/wiki.pl?Parallel_Port_Tester

these drives are optic isolated so the direction pins may need inverting .

You say it works under XP. Is that with the exact same hardware, or with a different PC?

Andy and CNC Basher, here are some more info

I am running a different PC than the one I was running XP on. The rest of the hardware (drivers cabling power supply etc) is the same.

I did some voltmeter measurements here are the results :

With everything Idle after booting and starting EMC2, I get

XDir is at 3.38 Volts
XStep is at 3.38 Volts
The + connector is at 4.28 Volts (is marked 5 volts)

If I jog in the - (minus) direction then the motor moves well and I read

XDir @ 0.07 Volts
XStep @ 3.17 Volts because of PWM

If I jog in the + (minus) direction then the motor does not move at all and I read

XDir @ 3.38 Volts
XStep @ 3.17 Volts because of PWM

The scope traces of XDir and XStep look normal

Any ideas on what is going on here ?

Jacques

How are the step drives wired to the breakout/parallel port?

If the step drives use a common 5V as a reference for their inputs
the 3.38V may well be marginal

That is, an OPTO isolator in the drive with one side at 3.38V and the other at 5V may well be partially on when its supposed to be fully off

jblain wrote:
I think you have a 3.3V parallel port, and it has not enough oomph to power the optocoupler on the DIR pin.
(why Step works is a mystery to me, though).

I think you need a different wiring scheme. (and this is the one on my stepper drives, even with a 5V parport).
There is 5V connected to the + of the stepper drive inputs (common on 3 drives, separate on the 4th).
The drives have internal current limiting resistors.
The parallel port either goes to 0V (so current flows, opto turns on) or 5V (or 3.3V in your case) and current stops flowing.
The assumption here is that your parport is high-impedence when "on" (3.3v) and that 5V won't push significant current into it.
I think this is the only way that a 3.3V port can work anyway.
Think as the pins as switches to 0V, not sources of voltage. And bear in mind that it is current flow through the opts which matters.
Asssuming you have Optos in the drives.

See page 5 of this document (actually for my stepper drives) for an example:
www.zappautomation.co.uk/pdf/manuals/PM542%20Manual.pdf

If my theory is correct then the other PC will have 5V on the parport.

However, you haven't told us the make and model of the drives (as far as I can see) nor what (if any) BoB you are using, so don't rewire until we have checked it out.

I tought I had attached the driver manualin a previous post, sorry. here it is.

I am not sure I still have the old XP PC I will check if it was 5 volts

regards

Jacques This attachment is hidden for guests. Please log in or register to see it.

What is BoB ?

Break Out Board, used to isolate the parallel port from the drives and sometimes other functions.

John