Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Mon, 4 Jun 2018 16:49:30 +0200

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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System