Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Fri, 27 Aug 2010 08:41:19 -0500

You did not say what module you used to write your driver.  If you use asyn then your driver should call pasynOctetSyncIO->writeRead().  That is guaranteed to be an atomic operation, so a writeRead from another record cannot interfere.  If you do write() followed by read() you will have the problems you are describing,  because a second write can occur before the first read is issued.

Are you using devGpib, streamDevice, asynPortDriver, or what?

Mark

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From: [email protected] on behalf of Andrew Wagner
Sent: Fri 8/27/2010 3:03 AM
To: [email protected]
Subject: GPIB and Record Advice

Hey everyone,

I've created device support and a driver for the Agilent 34970 MUX which I access over Ethernet via the PROLOGIX GPIB-Ethernet controller. I'm currently issuing three measurement commands in succession to read out three temperatures. The problem I run into is that occasionally one readout will not finish before the next is issued resulting in a LINK_INVALID error for the record. The MUX also reports the error -410 (Invalid command issued) when this occurs. Is there a good way to prevent asynchronous records that need to access the same device from "bumping into each other" in this way? If there were only two records I could set SDIS to the PACT of the other record but I have at least 3 and likely more records that need to access the MUX. Thanks very much for your help and advice.

Andrew Wagner

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System