Hi,
we are having problems with the strategy used by drvAscii to find line
terminators. We are considering changing it locally to solve our particular
problem and wonder if this would impact anybody else if the change were
propagated.
Our particular problem involves a compumotor 6000 controller. Most of the
time
it terminates strings with CR LF as requested but for some reason it sometimes
issues CR CR LF. This completely bamboozles drvAscii which has been told to
expect CR LF.
The termination detection of drvAscii resets the string pointer of the
prototype
termination string back to zero if it encounters 2nd or 3rd characters
that are
not of the expected sequence. I.e. (the spaces aren't real, just for clarity):
prototype string terminator: CR LF
received string: * T P E 5
CR CR LF /0
prototype string terminator pointer: 0 0 0 0 0 0 1
0 1
next expected terminator character CR CR CR CR CR CR LF CR LF
drvAscii then times out and the string is lost.
The solution seems to be to not reset the terminator string pointer:
prototype string terminator: CR LF
received string: * T P E 5
CR CR LF /0
prototype string terminator pointer: 0 0 0 0 0 0 1
1
next expected terminator character CR CR CR CR CR CR LF LF
Assuming the extra CR still in the string doesn't cause the subsequent
scanf in
drvAscii problems, then the received string should be returned to epics (we
haven't tried it yet).
Hope the examples are clearer than mud!
So, can anyone see any problems with this proposed change, or, a better
solution
cheers
--
Ian A Smith Telephone: (808) 961 3756
Joint Astronomy Centre Fax: (808) 961 6516
660 N. A'ohoku Place (808) 969 6591
University Park Web: http://www.jach.hawaii.edu
Hilo
Hawaii
96720
