[daviswoody]

Has anyone been successful in using GPIO to control an A axis brake? It looks like I could set an open/unmapped GPIO pin into output mode and then connect the digital output to the hardware pin.
Anyone’s experience with this and any HAL changes would be greatly appreciated.

[cncmakers001]

Use AC servo motor and AC servo driver for 4th axis can do the job.

[daviswoody]

An AC servo motor of the same size will have less torque at 0 RPM than a stepper. I could always oversize the motor but let's focus on the brake/locking_indexer implementation topics.

[kstrauss]

More expensive but why not use the Tormach USBIO unit? That should work with no HAL or PP changes.

[daviswoody]

...Tormach USBIO unit? That should work with no HAL or PP changes.

I'm not familiar with the USBIO but it looks like you can call M64/65 to switch the relay directly. If this is the case, that would be much easier than modifying PP.

If there are empty GPIO pins on the Mesa board it would also be nice to just be able to use those.