Sir,
There are several ideas that came to mind when I heard your problem.
1. The find home rountine for the motion boards in not latching. This means that the onboard OS reads the home switch as a digital IO and polls the pin. If you are communicating with the motion board while the find home routine is running, the onboard OS will slow down the rate that it polls the home pin and sometimes will miss finding the home position. As a result the board may find one edge of the pulse and slow down but not stop at the home position. The easiest way to verify whether this is happenning, is to open the Read per axis status VI and see if the home switch has been found (this VI can be run from its front panel). Also, there is an example on the web that uses the high-speed
capture (a latching input) to find the home position.
2. When the motion boards were intially designed, they were developed for much slower processors; therefore, the onboard operating system could not be barraded with commands from the host pc. Now that faster computers are coming out, the commands can be sent much faster and therefore putting the onboard operating system in an unstable state. However, this does not seem like your problem since you put a wait in your VI.
If you would like to post an example of what is happenning, I would be happy to help you find a solution.
Michael Halloran
Systems Engineer
Viewpoint Systems - Boston Office
National Instruments Select Integrator
www.viewpointusa.com
