Experimental Physics and
Industrial Control System

Emmanuel Mayssat <[email protected]> · Wed, 16 Mar 2005 17:21:15 -0800

I am convinced that some of you were faced with the same situation where
you had to read a timed input with an asynchronous device.

Well, apparently I am no different and would like to know what your
suggestions are.
Here is my situation:
The input signal is binary and periodic with period T=10ms.

The duty cycle is ~60% ( or the TTL level high is maintained for 6ms
while the TTL level low is maintained for the remaining of T)
If the signal becomes aperiodic ( always TTL high or TTL low ) then
there is an error ( wrong cable connection or device error )
I have an epics driver for the asynchronous device (binary input).
Here are the solutions I came across:
1/ The obvious one: write a new epics driver that will query the binary
input 10 times over 10 ms. If I get at least a 1 and a 0 then everything
is ok => pbi->val=1
2/ I looked at soft records that could run on the top of the existing
INSTIO record. That is my prefered way.

I came accross the seq record in the record manual. Is it an appropriate
use for it? Am I on the right direction?
Do you have any other suggestions?
Thanks,
--
Emmanuel Mayssat
Lyncean Technologies, Inc.
Direct: 650/320-8300 x409
Cell: 650/793-0626

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System