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Home Forum General General LinuxCNC Questions No step pulse output from parallel port

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TOPIC: No step pulse output from parallel port

No step pulse output from parallel port 03 Апр 2012 06:34 #18944

Hi folks. Please help a EMC2/Ubuntu newbie...

Finished my EMC2 installation a couple of days ago and since then I've taken the first small steps into the fascinating world of EMC2. I think I've managed to set up a bootable configuraition with stepconf. But now I'm STUCK!
I'm getting no step output on the X, Y and Z step pins. The direction output works fine. I'm testing with a LED+resistor between pin 25 (GND) and the various output pins. I get a dim light shifting on the direction pins.

What I've tried regarding the step pins is:
-Set step pins to "inverted". The light comes on, at the corresponding pin and thus I suppose the parallel port is OK !?
-Measured voltage om the pins when moving position manually in the software. Result is unclear, I get seemingly systematic fluctuations but only around 25 mV in magnitude. Absolutely not sure I'm having any pulse activity!
-I've tried various settings of timing including the slowest possible settings of 0,5 sec
-I found a similar topic in this forum, mentioning the possibility of monitoring the pin values in the Hal-meter, but in my case this is not helpful as the window minimize everytime a setting is changed.

So any input is appreciated - how do I figure out what I'm doing wrong?

Thanks in advance
Peter
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Re:No step pulse output from parallel port 03 Апр 2012 09:59 #18947

  • BigJohnT
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Step pulses happen pretty fast and you may not be able to see an led light up. The fact that you can see the direction pin change states is a good indication things are well. Do you have a driver or are you just experimenting with leds?

John
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Re:No step pulse output from parallel port 03 Апр 2012 10:33 #18948

Hi John
Thanks for your reply.
I do have a kind of driver. It's a homemade DIY design by Tom at: www.instructables.com/file/F5LOYU4F5R8QRL0. No timing info is supplied thoug. I've finished building the driver but when testing according to the mentioned procedure I do not get the supposed level-shifts on the IC pins - not even the input pins.
I'm now sure that there is some activity at the step pins as I can better registrer the voltage shift after raising the timing. You say that stepping happen very fast, but I thougth it was as simle as when I set step -timing and step space to 500000 ns I would get at pulse lasting 0,5 sec every 0,5 sec. Probably wrong???

As I'm now very much in doubt if I-m having a EMC2/ computer parport issue or the driver is the problem, Is there some way to find out? (other than buying a well tested commercial driver)

Kind regards
Peter
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Re:No step pulse output from parallel port 03 Апр 2012 12:03 #18949

  • PCW
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500000 nS is still just .5 Milliseconds...
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Re:No step pulse output from parallel port 03 Апр 2012 12:41 #18950

  • arch dude
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If you do not have an O-scope, you can choose to build a trivial latch. Alternatively, you can learn enough about HAL to "build" a counter on an input pin and then connect your (physical) output pin to the (physical) input pin. You may also be able to use the HAL O-scope on the input pin: I have not tried this myself.

If you trust the software, you could simply use the HAL O-scope on the output pin.
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Re:No step pulse output from parallel port 03 Апр 2012 22:51 #18957

Thanks!!
Messed up the suffixes quite badly. :silly: Of course 500000 ns is just 5 ms an not 0,5 s.
I do not have a scope and as mentioned I've not been able to use the HAL scope and I'm very far from beeing capable of understanding or editing HAL files myself.
I'm almost convinced that things are as suggested -that the time is just not long enougt to light up the LED, as I do see millivolt activity when jogging the axis. I'm going to dig a bit more in my controller function...
Kind regards
Peter
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