halcmd in pyVCP

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05 Nov 2010 08:34 #5094 by step4linux
halcmd in pyVCP was created by step4linux
hello,

I have a question:
can I submit halcmds (like unlinkp, linksp) in a pyVCP ?
can I do this in a user space component ?

thanks, Gerd

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05 Nov 2010 17:58 #5101 by cmorley
Replied by cmorley on topic Re:halcmd in pyVCP
no to pyvcp.
I believe yes in a component as you can include HAL's API and program in C.
What are you trying to do?

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05 Nov 2010 18:05 #5102 by step4linux
Replied by step4linux on topic Re:halcmd in pyVCP
I want to rewire the step/dir signals to swap motors.

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05 Nov 2010 18:41 #5103 by cmorley
Replied by cmorley on topic Re:halcmd in pyVCP
you could use tristae buffers controlled by a pyvcp button:
www.linuxcnc.org/docs/2.4/html/man/man9/tristate_bit.9.html
or create a component that does the same thing. (more compactly)
The idea is to steer (using the tristate buffer) the step and direction pins to 'A' motor or 'B' motor

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05 Nov 2010 20:44 #5105 by step4linux
Replied by step4linux on topic Re:halcmd in pyVCP
yes, this would be another solution, a kind of digital multiplexer with existing hal rt components, or my own one.
I thought about this also, but the "rewire" solution was easier to implement as a 1st step.
The hal scripts are very simple, and work perfect.
The only disadvantage is now, I have to start the scripts somehow, either by terminal or by another simple GUI.
So its not integrated in EMC.
Maybe I will start working on the mux. Another advantage of the mux would be, it can be interlocked by machine off or e-stop.

What is the real time performance of this kind of hal comps ? It must run with base period, because it has to switch step signals.

thanks so far

Gerd

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05 Nov 2010 21:11 #5106 by cmorley
Replied by cmorley on topic Re:halcmd in pyVCP
realtime comps run just like any other realtime program.
There is no difference in performance.

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05 Nov 2010 21:52 #5107 by step4linux
Replied by step4linux on topic Re:halcmd in pyVCP
I looked at the tri-state. Seems to be an efficient way to implement the mux.
Will try it.

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