Experimental Physics and
Industrial Control System

Eric Williams <[email protected]> · Thu, 18 Mar 2004 11:18:36 -0800

We recently hooked up some Wago modules here to monitor some
thermocouples through ethernet connections. Since we were dealing with
several isolated monitoring locations, one of the things I wanted in the
driver was the ability to make sure the ethernet connection was intact
through the EPICS channel status. We're using the DESY modification of
the TRIUMF modtcp driver
(http://www-kryo.desy.de/documents/EPICS/DESY/Records/wagoModbusSup.html),
and the driver did not show any change of status with a break in the
TCP/IP connection, but some of the code appeared to show that the basic
mechanism was already there. Fiddling around with the code a bit, I
came up with this mod:
In modtcpRead(), change the line:
 if (pPlc->pSock->tcpsFd == INVALID_SOCKET) return -1;
to:

if (pPlc->pSock->connecting || pPlc->pSock->tcpsFd ==
INVALID_SOCKET) return -1;
Similarly change modtcpWrite(). The timeouts are long, but the record
status does eventually go INVALID when the connection is lost, and then
recovers when it is reestablished.

--

Eric Williams

ALS Controls

Lawrence Berkeley Lab

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System