Re: Parsing problem with stream

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Hi Richard,

You can limit the scope of a checksum like this: %1<xor8ff>

A checksum like %A.B<...> ignores A bytes at the beginning and B bytes 
at the end.

For fixed-length input you can use maxInput=number_of_byes; instead of a 
terminator.

Dirk

On 04.06.2018 16:30, Lucock, Richard M wrote:
> Hi,
>
>      I am having problems parsing data from a serial device (ie
> obtained using asyn & stream). The normal protocol is to send a
> message (with checksum), wait for an ACK character, then read the
> reply (which has a checksum).
>
> If I read the ACK and the reply on one line, using the protocol below:
>
>     read_version {
>        out STX, "001?f" ETX, "%<xor8ff>";
>        in ACK, STX, "001 f%[^\003]", ETX, "%<xor8ff>";
>     }
>
>
> then I get the correct data into my 'stringin' record, but the shell
> reports that the checksum is wrong (presumably because the ACK has
> been included in the calculation). If I separate out the ACK and the
> reply inputs:
>
>     read_version {
>        out STX, "001?f" ETX, "%<xor8ff>";
>        in ACK;
>        in STX, "001 f%[^\003]", ETX, "%<xor8ff>";
>     }
>
> then the shell reports no errors, but nothing is placed in my
> 'stringin' record.
>
> The messages have no terminators, which I guess is part of the
> problem. I have tried playing about with 'extrainput', 'maxinput' and
> 'wait', with no luck. Does anyone have any suggestions for dealing
> with this ?
>
> Thanks,
>      Richard