HI
I didnt have exactly the same problem,but have troubles with the short pulses of
Mach3 which are configurable from 3 - 25µs.My optocouplers are too slow to transfer this pulses properly(Masured with Oszilloscope).I used the Optoboard from Dmitri Shilov and PC817 couplers.I think the Opto PCB from Alan seems to be OK.
reineke |