Experimental Physics and
Industrial Control System

[email protected] · Tue, 7 Dec 2004 16:46:50 +1100

Hi all,

I'm hoping that someone out there can help me with what is probably a very
elementary piece of EPICS programming, but which I can't seem to get my
head around.

Our EPICS applications will have many output records (ao, bo, etc) for
writing commands to devices in order to do such things as setting them into
particular modes, like On/Off or Enabled/Disabled.  What I want to be able
to do is have the Device Support/Device Driver read from the device at
record initialisation time and set the initial state of the record to match
that of the device.  It shouldn't change the state of the device.

This is where I run into problems.  I've read Chapter 12 of the IOC
Application Developers Guide and understand the init_record() procedure.
As Andrew Johnson said in a recent tech-talk post:

 "It's the device support's init_record() that is responsible for doing the 
 initial value readback from the hardware into RVAL if it can, (or into VAL 
 and returning 2 instead of 0)."                                            

I also understand how to use the asyn drivers devGpib template to create a
device driver and have successfully used this to communicate to a few
devices.

However, I haven't been able to work out how to get devGpib to read the
initial value back from a device for an output record at initialisation
time.

If someone out there could help me with this, or even provide examples of
code which does this, it would be greatly appreciated.

Steve Banks
Australian Synchrotron Project
Department of Infrastructure
Level 17, 80 Collins Street
Melbourne   VIC   3000
tel:  +613 9655 6303
fax:  +613 9655 8666
web: www.synchrotron.vic.gov.au
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System