Need Help!- Parallel Port Voltage

[blue_steel]

This could be a stupid question but when you measure the voltage on your parallel port with your multimeter shouldn't you see the standard 0/5v signals or therebouts?

I'm just trying to test my L297/298 driver with a small motor.

I'm using the EZCNC controller software.

I can see the voltage fluctuate on the appropriate pins when I jog or command movement but it's really weird voltage levels like 178 mV.

The parallel port on this old computer could be shot for all I know. Or is it possible that these voltage levels are floating since there's no load?

Anybody see what I'm doing wrong.

[cgm003]

blue steel a voltmeter will not show correct voltage on a data line as the signal is a fast pulse. To see the voltage pulse you would need a oscilloscope.

[blue_steel]

Okay,
Does that hold true even for signals that are held high or low? For example the direction signal should be either 0 or 5V. I assume it is held high or low for the duration of the commanded movement which could be several seconds.

[cgm003]

The answer is "depends" the direction signal may be a consatant HI or it may be a single pulse.

[blue_steel]

cgm003

I looked at the controller software and there is a setting for the direction pulse width. It's not simply left high or low like I thought. So I just adjusted that and it all worked.

Thanks a bunch.

[cryscrys]

in my experience the output of the parallel port was 5volts and 0 volt

[ger21]

The direction signal should stay at either0V, or 5V, depending on which direction you're going.

[JustPlaneSweet]

Note that 'modern' computers are putting out 3.3v instead of the 5v we need for cnc. Use a parallel port adapter card to get the full voltage. I had to do this to get EMC2 to drive a Xylotek card.

Stan