Mach4 tutorial - Custom signal mapping

This tutorial will show how to trigger an action in Mach4 based on signal change. In Mach4, user customization options are available via simple LUA scripting language.

We will map the signal to one of the PoKeys inputs and configure it to trigger the ‘Cycle start’ function. We assume you have configured the PoKeys device in Mach4 already – if not, follow this guide: Mach4 CNC Controller Software with PoKeys

Mapping the signal

Open Config > Mach configuration dialog and switch to ‘Input signals’ tab. Select your PoKeys device and appropriate IO using the drop-down boxes. We selected pin 15 in the following screenshot

Mach4 - PoKeys input — Mach4 – PoKeys input

Confirm the configuration and close the dialog.

Opening the signal mapping code

The signal mapping code is a part of the Mach4 screen (window) initialization code, accessible from the screen editor. Go to ‘Operator >

Mach4 - edit script for PoKeys IO — Mach4 – edit screen

Once the screen editor is opened, one has the access to all parts of the Mach4 GUI parts. For mapping the signal, we will edit the Screen Load script. In the list on the right, locate the top element in the list (also the name of your screen – e.g. wx4, wx6 etc.) and click on it. In the lower left corner, locate the ‘Properties’ pane. There is a ‘Events’ button that will open the list of Mach4 scripts that are a part of the screen.

Mach4 screen editor - switch to events — Mach4 screen editor – switch to events

Locate the ‘Screen Load Script’ and click in the field on the right. A button (with ‘…’) will appear that will open the script editor when clicked.

Editing the code

Locate the list of function declarations in the code that look similar to the code highlighted in green and red boxes on the image below.

Mach 4 - signal script — Mach 4 – signal script

This part of the code initializes the list of signals and their respective function handlers. In the default screen, ISIG_INPUT0 signal has an empty function declared, while the ISIG_INPUT1 signal has a function with some example code that shows how to trigger the function in Mach4.

Let’s add the following code to the ISIG_INPUT0

    if (state == 1) then   
        CycleStart()
    end

The code now looks

Mach4 tutorial - Custom signal mapping of signal 0 to Cycle start function — Mach4 tutorial – Custom signal mapping of signal 0 to Cycle start function

Save the code, then exit the screen editor (again via Operator > Edit screen menu). Save the changes to the screen and test your new shortcut.

Adding more signals

If you look at the code in the script, you will notice that you have somewhere in the beginning

---------------------------------------------------------------
-- Signal Library
---------------------------------------------------------------
SigLib = {

Then, one block as following for each signal

[mc.<signal name>] = function (state)
 < code >
end

So, SigLib is a Table name, which contains handler functions for all signals in the list. The SigLib ends somewhere later on (around row 70) with a ‘}’. To add a new signal handler, make sure that you insert it in the Table and that you put a comma at the end of it.

---------------------------------------------------------------
-- Signal Library
---------------------------------------------------------------
SigLib = {
[mc.SIGNAL1] = function (state)
 < code >
end,
[mc.SIGNAL2] = function (state)
 < code >
end,
[mc.SIGNAL3] = function (state)
 < code >
end,
...

[mc.SIGNALn] = function (state)
 < code >
end
}

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