RE: Initial value readback from hardware into output records

[Steven.Banks@doi.vic.gov.au]

Hi Stephanie,

Thank-you for this.  I understand how to do your solutions (1) and (3), but
it is solution number (2) which I am primarily interested in:

>(2) For records that have readback available and initialization device
support, >the setpoint is set to the readback by device support at the
proper time in >iocInit.

I have never seen any concrete examples of how to do this in the real world
and would appreciate some help in understanding the details.  For instance,
I presume that the readback must be obtained during Device Support's
Init_Record() routine but I have not yet fully grasped how this happens.
For instance, the IOC Developers Guide talks about Driver Support and I
presume that Device Support must call an API provided by Driver Support to
get the readback value.

But where do I obtain these low-level drivers from?  Do I have to write
them myself?  Or are they generally available somewhere?  Or does Device
Support just talk directly to the hardware, and if so what does EPICS
provide to help with this?

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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