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OT?: break up an incoming data stream into fixed length lines? in bash?


At Fri, 6 Apr 2018 11:04:08 -0700 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> I'm using U16.04 to read data from a sensor. The incoming serial data
> stream has no newlines, just continuous bytes. In the datastream the
> letters B and M occur together at the start of every 24 byte
> subsequence. I'm reading the data using getserial with appropriate
> speed and parity parms. I don't see a simple way to break it up into
> lines with each line having 24 bytes. Does anyone care to suggest a
> method? I'd use a bash function if there is one.

You are going to have to use low-level serial I/O.  I am presuming we are 
talking about RS232/485 (/dev/ttySnn) OR a USB/Serial device (/dev/ttyUSBn or 
/dev/ttyACMn).

Commonly, that would mean have way to much fun coding in C/C++, but it is 
actually possible to do that with Tcl -- something I have done for various 
serial-based Model Railroad interfaces.  (It might be possible with Python, but 
I don't use Python, so I have no clue).

There is Tcl code libraries under 

https://github.com/RobertPHeller/ModelRRSystem

That do low-level serial I/O in Tcl (eg read one character at a time).

Look in these sub-directories:

trunk/Scripts/CMri
trunk/Scripts/CTIAcela
trunk/Scripts/XPressNet

They all use much the same low-level I/O structure.

> 
> TIA,
> 
> Dave
> 

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