generic programmatic gcode comunication needed

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21 Dec 2020 10:44 #192616 by khk
Hello to the community. I am new to LinuxCNC. I have a project on Beaglebone Black doing advanced analysis and tracing on specific chips using a CNC3018 as a probe mover and lifter. So I want to integrate the probe movement in my analysis application (NO GUI!)
I'm asking for a code extract or example how to send gcodes to the CNC3018 controller connected via an USB bridged serial connection with buffering and position readback.

any idea ?

Merry Chrismas to all of you, Karlheinz

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21 Dec 2020 11:30 #192622 by BeagleBrainz
Linuxcnc does not work with the GRBL type controllers. (Or USB for machine control, USB pendants are supported) nor any of the boards designed for Mach 3/4 whether USB or Ethernet.

If your controller is a GRBL type controller:
With GRBL, the grbl board (usually Arduino) is the motion controller.

With Linuxcnc, the PC running Linuxcnc is the Motion Controller, and it will either "bit bang" the step & dir pulses to a Parallel Port, or send the step & dir info to a MESA FPGA card. This is the simple explanation.

The code to send gcode to your machine should be able to be extracted from one of the many "sender" projects or there maybe some info on the GRBL github page.

If your controller works with Mach3/4.
Well as Mach is closed source........

As for the CN3018...
I'm not sure if you will get the accuracy you require with ACME lead screws and no real fixed bearing for the lead screws. They are really just a basic machine mechanically. Unless of course you have addressed the shortcomings by using ball screws, having a fixed bearing at one end of the lead screw and a floating bearing at the other. I would also look into a low backlash coupler between the steppers & lead screws. Im thinking that you require high accuracy.

As for positional feedback.....
That would depend on the type of scales/resolvers you are using.

Now the BBB has 2 nice PRUs (quite good for step\dir generation) and quadrature endcoders.
The Machinekit project does support these on the BBB.

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21 Dec 2020 21:33 #192717 by khk
Project is done. I did everything in python including serial communication.afer reviewing some sender applications. The overhead isolating the related code was to big

thank you
The following user(s) said Thank You: tommylight

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21 Dec 2020 23:18 #192746 by tommylight
That was quick !
Nice.

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