0 bytes on VISA Read?

[GReaper]

'lo all,

Follow-up time here.  The problem was not in the read but in the preceeding write of the polling query command.  The device was never getting the poll command correctly when I sent it as a 2 character string.  Thus, nothing ever came back to read.  When I broke it up into two visa writes with a 40 ms delay between the instrument correctly processed the command and sent back my packet of information.

NI-Spy said the write was successful as a two character string, but the device just blissfully ignored it until I sent it character by character.

Hard learned lesson here.  When your read is seeing nothing, your previous write may be the cause.  Dang, seems so obvious now!

[Ben]

Thanks for the update Greg.

That widget must be as old as me!

I have this old scratch-built I/O device that had a delay built into the code to throttle the resonse back to the PC to make sure the PC did not miss  any data. Your situation sounds like the same thing backwards. I guess they thought that nobody could ever type that fast.

Ben

[Dennis_Knutson]

It doesn't necessarily have to be an old widget. I have to regularly provide an inter-character delay to products I test. I posted a VI that will do that at http://forums.ni.com/ni/board/message?board.id=170&message.id=54750#M54750.

[Ben]

Well thank you Dennis and Greg.

Hopefully I'll be able to remeber that when I run into it myself.

Ben