I would also like to know the answer to this. I have Gecko 320 servo drivers and have to push the enable button physically every time it is turned on.
Can the software enable/disable the servos on startup or power down so no need to push the switch?
The "enable button" where? Connected directly to the G320s? Or are these G320Xs? And is this from your PMDX-411? If so, I would recommend getting the PMDX-126. It has an interface for the G320 ERR/RES signal built in and will automatically pulse that signal whenever Mach is "enabled" so your servos are automatically enabled. And it will interface to your prox sensors.
You could (maybe) connect an output from from the PMDX-411 directly to the ERR/RES. In Mach4, map the "Enable #0" output signal to that SmartBOBUSB pin and keep a red "X" in the "Active Low" column. Then whenever Mach4 is enabled, that pin will go to +5V, which will enable the G320s.
WARNING: This will prevent the G320s from ever being able to report a fault back out on the ERR/RES pins.
If these are G320X drivers, you can tie the ERR/RES to the ENC+ terminal to force them to be always enabled. In fact, you can also do that with the G320 drivers. In both cases this prevents the drivers from reporting an error.