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List:       rxtx
Subject:    Re: [Rxtx] clear input buffer on startup.
From:       "M.Dec-GM" <mariusz.dec () gmail ! com>
Date:       2011-01-20 6:17:38
Message-ID: 07CF7AAE837349EF920DB9DEAE0952BB () mdam3
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----- Original Message ----- 
From: "Gerrit Polder" <gerrit.polder@solcon.nl>
To: <rxtx@qbang.org>
Sent: Wednesday, January 19, 2011 9:37 PM
Subject: [Rxtx] clear input buffer on startup.


> how can I clear the input buffer on startup,

Before opening port you are creating a new instance of the port in Java and 
OS.
In this "time point" java starts RXTX native part and this part of RXTX 
connects to device layer in OS.

Next step is opening the port.
If you have incoming data in this moment, it means that device layer don't 
cleans buffers while starting (driver's feature - programmer's 
mistake/error) or external device  is sending data and OS is receiving it.
So in fact, flushing/cleaning input buffer helps a little because you never 
don't know what has happened.

!! I haven't never seen waste data in RXTX buffer on open(), so it looks 
that RXTX and my OS drivers (FTDI) are ok. !!

What to do:
Data in EACH transmission needs header and trailer, checksum and length of 
the block are very useful as well.
If you are receiving data, you have to identify what data means - you have 
to identify block and read from this block
Your incoming part of the app should look for the first header and flush 
data until header will be identified.
Later you should wait for the trailer or read data using packet length 
(usually after header), finally check the cheksum (usually on the end, may 
be in the role of the trailer).
Succesfullly checked data should be transferred to app, damaged data should 
be flushed.

Regards
Mariusz



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