RE: GPIB and Record Advice

["Mark Rivers" <rivers@cars.uchicago.edu>]

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: tech-talk-bounces@aps.anl.gov on behalf of Andrew Wagner
Sent: Fri 8/27/2010 3:03 AM
To: tech-talk@aps.anl.gov
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