Reading a synchronous input with an asynchronous device.

[Emmanuel Mayssat <emmanuel_mayssat@lynceantech.com>]

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