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Entry  21 Sep 2004, Konstantin Olchanski, , ODB-EPICS gateway 
    Reply  21 Sep 2004, Stefan Ritt, , ODB-EPICS gateway 
Message ID: 39     Entry time: 21 Sep 2004     In reply to: 38
Author: Stefan Ritt 
Subject: ODB-EPICS gateway 
The easiest way to achieve this is to write a new class driver, probably derived
from the multi.c class driver. One has just to rename all "output" with "write"
(or better "ODB2EPICS") and all "input" with "EPICS2ODB". The multi class driver
handles already a factor/offset for each channel (which could be 1/0 of course),
a threshold to update the ODB/EPICS only when a value changes significantly, to
retrieve labes from the bus driver (EPICS labes -> ODB settings), automatic
event generation and error handling. So it would be a good starting point.

What one gets from the class driver in the ODB is:

        Input[]     <--- read from the bus driver (float)
        Output[]    <--- witten to the bus driver (float)
        Names Input[]        <--- human readable names
        Names Output[]       <--- human readable names
        Update Threshold[]
        Input Offset[]
        Input Factor[]
        Output Offset[]
        Output Factor[]
              DD/   <--- parameters for Device Driver
                 ... Epics addresses, flags etc.
              BD/   <--- parameters for Bus Driver
So if one uses the standard mfe.c code together with the multi.c class driver
and epics_ca.c device driver all what is left is the following:

- replace cd_gen.c by multi.c in the examples/epics directory
- break down the already existing flags into enable epics/write/events
- maybe add th EPICS read period

The last two things should be done in the epics_ca.c device driver, so one can
use the multi.c class driver without any change. Event generation and error
handling then comes for free.
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