Hi Peter,
yep, I just tried the simulator with SGP and it worked fine. I think the issue is to do with time. When connected to the simulator a movement of say 2000 steps is virtually instantaneous. However, when connected to a real focuser 2000 steps can take some time to execute.
While the motor is moving there is a chain of command. The PIC is aware the motor is moving because it is physically driving the motor. So the user initiates a move and client sends the command to the driver via ASCOM. The driver interprets the command and sends a command to the PIC via USB. The PIC receives the command & starts the motor moving. Now the client wants to know what the motor is up to so polls the driver for motor status, in tern the driver polls the PIC for motor status. PIC reports motor moving to the driver, driver reports to client and client reports to user .... an so on until the move is complete.
So if the client is waiting for something to happen and it doesn't happen or takes to long it might get upset and throw an exception or error. The part I'm a bit confused about is that the ASCOM conformance checker checks for correct driver response and is happy. So I am not sure why SGP is getting upset.
These sort of problems are what make development interesting
Dave