Using Pin Changes for Timing (and light debugging)

Making pin changes in the code can allow you to do timing using a logic analyzer or a scope. You can use it for some minor debugging or debugging where the timing is hard to tell with a debugger.

Pin changes are not a substitute for a proper debugger.

How to debug with pin changes in G2

1. Go to the motate_pin_assignments.h file, e.g. in the v9_3x8c/motate_pin_assignments.h file, and swap the pin you want to "steal from" with the debug pin you want

Say spindle change:

pin_number kSpindle_EnablePinNumber         = 112;

to

pin_number kSpindle_EnablePinNumber         = -1; // was 112

Warning -- don't use the input pins for timing via pin changes. They have an R/C filter on them and will slew the output significantly. You should limit the debug pins to those that are normally outputs, and have a screw terminal or other pinout.

1. Assign one or more debug pins to pins you want to temporarily "take over".

pin_number kDebug1_PinNumber                =  112; // using the spindle pin temporarily
pin_number kDebug2_PinNumber                =  -1;
pin_number kDebug3_PinNumber                =  -1;
pin_number kDebug4_PinNumber                =  -1;

1. Then at the top of the file you want to instrument, put (or, more likely, uncomment) the OutputPin<> definition. For example, at the top of plan_exec.cpp now is:

// This next "using" line just has to be in the file before you use OutputPin<>. It likely already is.
// You don't want it in the file twice, or the compiler will bark at you.
using namespace Motate;
//OutputPin<kDebug1_PinNumber> exec_debug_pin1;
//OutputPin<kDebug2_PinNumber> exec_debug_pin2;
OutputPin<kDebug3_PinNumber> exec_debug_pin3;
//OutputPin<-1> exec_debug_pin3;

1. Now, in that file, anywhere you want to set the pin:

exec_debug_pin3 = 1;

and the clear it:

exec_debug_pin3 = 0;

and to toggle the pin:

exec_debug_pin3.toggle();

PLEASE -- don't git commit the changes to the motate_pin_assignments.h file.

ALSO -- avoid putting more than just the pin changes in. if...then statements around the pins can easily have side effects, and it you're just timing or doing light debugging, you don't want that.