cmcgrath5035

tinyG with $2mi=10 should work fine with this external driver.
I had to read the gecko document a couple times too, first I have seen a driver with fixed microstepping.

Does Y move at all? If you command Y to move 10mm, how far does it move?
What Voltage are you driving the motors with, and what is your current setting for the gecko?

The LED behavior you report sounds OK.
The red flashing on reboot/startup is the bootloader waiting for possible communication with Avrdude wanting to download new code.
Once boot delay is done, tinyG starts up with all motors energized at current location for $mt time, in your case, 2 seconds.

Your $2pm=2 setting is the usually prefered value, motor energised when any motor is moving. If things still not working right you can try $2pm=1, but that is overkill.

Your $2tr = 24.9350 mm is a bit strange, too large for a screw machine but on the low side for a belt machine. Are you sure it is correct, and not the right value for a different controller? I am not aware of an available belt and pulley combo that would yield 24.935mm per revolution

The delay on command send does sound strange.
Are you sure of proper connection to step, dir and enable plus ground?
Schematic are here https://github.com/synthetos/TinyG/tree/master/hardware/v8schematics

I love the smell of burning plastic in the morning :<

The simple answer would be no.

tinyG provides On/Off and direction control signalling for a spindle as well as a continuous, single phase PWM stream whose duty cycle is related to the S command via a programmable linearization of a range of speeds.
G code commands M3, M4 and M5 as well as S are the controlling parameters.

It might depend on what you are really trying to implement.
If you are manually coding a Gcode stream to implement some sort of robotic movement, you could code complex XYZ motion and manually edit in continuous rotation on a rotary axis (A,B or C), I suppose

Maybe a picture of your stuff would help.

Electrolytic – nope, you need good high frequency cap. 0.22uf ceramic or mylar, etc.

Make a two wire connection between tinyG and each switch individualy; one wire ground, one wire the other switch terminal. The two wires should be shielded, typically two wire shielded is twisted pair but I understand your comment.
Twisted pair is what is most available. Connect the shields together and ground them to Vmot “-” terminal. The four ground wires, one from each cable, to the Gnd on port terminal block.
You can ground the structure of your machine if you want, separately, but do not consider the machine to be grounded for switch wiring purposes

I could read your description above to say that you run 4 leads plus one ground between tinyG and the machine, but am not sure that is what you are saying. That would inevitably lead to a cable breakout mess at the machine end, as the switches ar in different physical locations.

This is a good reference to read thru https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Setup-and-Troubleshooting#limit-switches

Noise mitigation is a combination of art and engineering.
I would start with a focus on the wiring of the limit/homing switches

You don’t need a lot of current capacity, so 18, 20 or 22 ga shielded twisted pair cable would suffice and easier to deal with.
Here is just an example https://www.amazon.com/Custom-Cable-Connection-Conductor-Stranded/dp/B071DFHKRB/ref=sr_1_4?ie=UTF8&qid=1545042425&sr=8-4&keywords=shielded+2+conductor+cable

Could be solid or stranded conductors, stranded more flexible.

Make no shield connection at the switch end (machine end).
At tinyG end, connect all shield drain wires together and connect to the ” – ” Vmot terminal.
Use the red wire for the input terminal (e.g. Xmin, Ymin, etc) and the black wire connects to the gnd terminal on J8 terminal block

Try to route the switch wires separately from the stepper cables and the spindle drives.

You asked “Will [setting $gppa=1} change require me to recalibrate all axis? Ans:No, but you likely figured that out already

Suggestion: From console set $p1pof=0.00. This will turn off the PWM LED when you machine is at rest. Mostly cosmetic, but might help with the next question.

When the machine stops midway thru your job, do you get flashing LEDs or other indicator?

From staring at your board wiring diagram, I believe I see an issue.
It appears that your switch connections are single wires, not shielded twisted pairs. But I can see the whole run, so it might be OK but out of view.

Do you have a separate power supply for the spindle?

Limit switch interfaces are very sensitive to noise spikes, even when using NC switches.
A symptom of a limit switch activation would be a flashing LED.

Have you reviewed https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Setup-and-Troubleshooting#limit-switches-fire-in-the-middle-of-a-cutting-job ?

Thanks, good info to work with.
Some housekeeping, looking at your most recent $$
1. Set $p1pof=0.0 With that, the Spin LED will be off when the spindle is turned off
2. Set $asn=0 to turn off the A axis limit switch input.
3. With tinyG, all switches share the same config, NC or NO. Switches are individually configurable in G2Core (the next generation)
4. I am somewhat concerned with you switch (pogo pins) but they used to work so probably not the issue. tinyG has debounce software conditioning the input signal that has been experimentally optimized for typical microswitches. The contact bounce from you pogo setup might be significantly worse, but probably OK.

I think I might see your issue.
Your first $$ post showed the $xtr=$ytr=40mm.
After $defa=1 it is 5mm, so your axes are moving 8 times faster than tinyG is computing. So the reported movement of -178mm to (apparently)find home on X is actually 8*178mm, which does not make sense since your physical machine is not that large.

Fix $tr values (and microsteps while you are at it) and see if that helps.