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Subject: Some questions from a first-time driver author
From: Zik Saleeba <[email protected]>
To: [email protected]
Date: Mon, 30 Jul 2018 11:41:07 +1000
I'm new to EPICS and I'm writing a new driver for an IP connected xray pulse detection device. I was wondering if more experienced people can help me with a couple of questions I have.

I've written a driver using PVs as the method for accessing the device state and it works but in some ways it seems unnecessarily awkward:

1. I use separate longin and longout record types for getting and setting integer device variables. Is it possible to use just a single record for both input and output of the same variable? That seems like it would avoid unnecessary duplication and confusion between the two records.

2. My C code registers dsets for each of the input and output types I use. These each provide an init method and either a read or write method depending on the direction. PV client writes result in immediate calls to my write callback from the dset which is what I expected but PV client reads only access the internal stored state of the record, they don't call my read method. Instead I have to get the value into the record using a SCAN field to regularly update the record. This seems to call the read method correctly. Is there a way to get the PV read to directly call my read method so I can provide the instantaneously correct value rather than just the most recently polled value?

Thanks for your help,
-- 
  Zik Saleeba, Senior Software Engineer
  [email protected]

Replies:
Re: Some questions from a first-time driver author Dirk Zimoch
Re: Some questions from a first-time driver author Mark Rivers

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