[bojan]

Following up on my LXD75 modification..
Recently I was given Arduino MEGA board with Steve's shield (courtesy garymck).
This means the next step in life of my LXD75 will be latest OnStep firmware + 400s/rev steppers + timing belt reduction (most likely 60/16) using standard (and cheap) parts from ebay.
I already tested the system on bench, mount GoTo will be VERY fast, judging from time it took motors to stop on target on the other side of the sky (control was from CdC).
Steve's board has the same problem as almost all Pololu drivers based on DRV8825, available on the market: DECAY pin is left floating, which means chip works in mixed decay mode.. which is not adequate for motors I have (Longs 17HM0423, 2.3A). Tying this pin to 3V on chip regulator solved the problem (see attached pic), so motors are running smooth now in 32 /ustep mode (perhaps there is a bit more noise, but this issue actually depends on motor design and manufacturing quality - the noise people complain about is generated in windings if they are not wound tightly enough or not immersed in resin to prevent them from vibrating).
This also gave me an incentive to improve EQ6 as well (currently this mount works with OnStep w/o switching /u stepping). I only need to connect 6 additional wires from my driver board (inside mount) to connector (and controller). And, using STM32 with OnStep will add even more to GoTo speed performance (not that it is REALLY needed...)
I will post the progress here..