Experimental Physics and
Industrial Control System

I am writing EPICS code to interface with a custom device.  The device protocol is fixed-length messages.  I can read and write the message parameters with Stream Device, and have done so successfully except for the fixed-length string, which I have had to bypass in assorted ways.

The output command message has the Python struct format "ii128s12i".  The input message has the Python struct format "128s12ii".  The "12i" refers to 12 parameters, passed or returned.

My two questions are:

1) How can I parse the fixed-length string?  The normal string-handling routines fail either because of terminator characters in the string or because the string is two long.
2) I handle the parameters by having a PV for each parameter, and a separate "group" of PVs for each command.  Is this best practice?

Thank you,

Iain Marcuson.

Replies:

RE: Packed Data Message Formats With Fixed-Length Strings Mooney, Tim M.

Re: Packed Data Message Formats With Fixed-Length Strings Dirk Zimoch

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