VISA Serial Comm.

[bhaldeman]

I am trying to check the position of a motor through the serial port. I am building array that corrolates actual motor position with a seperate optical readout. I need to send a command to the motor controller to "ask" for current position, then "read" the response back through the serial port. To read back, currently I am checking for bytes at the serial port, and then reading if there are bytes. I run that check in a while loop that needs at least a 25ms wait or the system hangs.

This 25ms accuracy is not good enough. Is there a way for the serial port to tell when it has bytes waiting rather than having a very fast loop continually checking it?

thanks a ton

ben

[JohnRH]

...  Is there a way for the serial port to tell when it has bytes waiting rather than having a very fast loop continually checking it?

thanks a ton

ben

2596[/snapback]

Yes there is.

One way might be to use VISA Events to notify you of the arrival of a serial character. First you have to Enable the event, and then you can wait on it.

Another option is to take advantage of the timeout on the VISA read function. If you Read one character with a large time out (500ms or so), the Read function will return as soon as one character is received, then you can proceed to read the remaining characters. If it times out then you can clear the error and repeat.

I'd really like to post images of some code to make this all a little more clear but I can't seem to figure out how.