I have been testing the PoKeys 56E's encoder inputs with the new plugin that Brian is at this time developing.
I have been very impressed so far
I have one of the encoder inputs connected to the buffered encoder outputs on a servo drive which has a 4000rpm motor with 2000line (8000ppr) encoder. At full speed that equates to 533KHz. I have not lost a single count even when running the motor at full speed over a period of hours with frequent reversals at 1000 revs/s/s acceleration set.
This opens great possibilities to me, it means I can basically have encoder feedback to Mach which could be monitored for position errors if wanted but what I really am looking forward to is being able to reference the machine once when I start Mach, it could actually just be done once and never again unless 56U and encoder are powered down but I will personally home on each start of Mach. This means if I E-Stop or Disable/Enable drives I could have a message pop up to ask if I want to update Machs machine coords to the encoder position if it is different. This is great for me as all axis will lose position to some point when an E-Stop situation has occurred or drives are disabled. Even steppers will lose position if they are disabled as they will jump to the nearest full step. With encoder feedback Mach would know and allow you to update if you choose.
Another possibility is to have encoder index homing which will be very accurate. Currently I do this external to Mach in my servo drives but being able to do it inside of Mach means that servo drives without this capability or even steppers could be homed to an index pulse as long as you have an encoder fitted.
So in short as long as the standby power to my servo drives logic and the power to the pokeys is kept alive the actual axis position will always be known by mach when it starts and can be updated if required
Hood