How to debug a macro

Description

Looking for information about how Macros are evaluated and how one could debug them when they are going wrong.

Version	cncjs desktop osx 1.19.17
CNC Controller	Grbl
Hardware	Laptop
OS	OSX

Details

I have a macro I’m trying to suss out that should be able to find the center for WCS setting by probing three points within a circle cutout. However, when I run this, I eventually get something like:

G0 XNaN YNaN

which, as I have some passing familiarity with Javascript, is JSpeak for “you did a bad thing with numbers and I’m confused”.

However, when I plug all these values into a JS console in my browser, it all maths out just fine.

So, while I’d love someone to say “Oy, line 54 has error X on it” to fix my macro, what I think might be more helpful is: How does one debug macros? How are they evaluated?

(Based on an answer in #250 it looks like the data in between brackets [] is just, like, eval()ed? I couldn’t quite figure out where the codebase does this to understand it…)

Here’s the macro in question:

;Start with probe in hole, BELOW Z surface

; Wait until the planner queue is empty
%wait

; Set user-defined variables
%PROBE_DISTANCE = 20
%PROBE_FEEDRATE_A = 150
%PROBE_FEEDRATE_B = 50

; for restoration at the end
%UNITS=modal.units
%DISTANCE=modal.distance

G91 ; Relative positioning
G21 ; Use millimeters

G10 L20 X0 Y0 ; set current position as xy zero for now

; Probe rear, slight right
G38.2 X1 Y[PROBE_DISTANCE] F[PROBE_FEEDRATE_A]
G1 Y-2 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 Y3 F[PROBE_FEEDRATE_B] ; probe again, slowly
%p1x = [posx] ; set the x/y coords for later
%p1y = [posy]

; set back to absolute mode and return to original spot
G90 
G0 X0 Y0
G91

; Probe 45deg
G38.2 X[PROBE_DISTANCE] Y[PROBE_DISTANCE] F[PROBE_FEEDRATE_A]
G1 X-2 Y-2 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 X3 Y3 F[PROBE_FEEDRATE_B] ; probe again, slowly
%p2x = [posx] ; set the x/y coords for later
%p2y = [posy]

; set back to absolute mode and return to original spot
G90 
G0 X0 Y0
G91

; Probe slight rear, far right
G38.2 X[PROBE_DISTANCE] Y1 F[PROBE_FEEDRATE_A]
G1 X-2 F[PROBE_FEEDRATE_B] ; back off a bit
G38.2 X3 F[PROBE_FEEDRATE_B] ; probe again, slowly
%p3x = [posx] ; set the x/y coords for later
%p3y = [posy]

; Figure out proper center https://stackoverflow.com/a/30106470 and set it
%ma = [(p2y - p1y) / (p2x - p1x)]
%mb = [(p3y - p2y) / (p3x - p2x)]
%cx = [(ma * mb * (p1y - p3y) + mb * (p1x + p2x) - ma * (p2x + p3x)) / (2 * (mb - ma))]
%cy = [(-1 / ma) * (cx - (p1x + p2x) * 0.5) + (p1y + p2y) * 0.5]

; Return to origin, move to new center, set center
G90 
G0 X0 Y0
G91
G0 X[cx] Y[cy]
%wait
G10 L20 X0 Y0

[UNITS] [DISTANCE] ;restore unit and distance modal state

[chuyskywalker]

Worked like a charm, thanks!

[chuyskywalker]

Hey, that example code looks familiar! Jokes aside, very cool and should help a lot in further runs of things, thanks 😃