Re: [Discuss-gnuradio] gmsk2 - CRC and whitening

[address@hidden]

Good suggestions, will look into implementing CRC16 with hardware and the
whitening for small payload.

Processor - Atmel AT90S8535 - face turns beat red. =)

Looking at the packet.sink code, it looks like it's independant of the CRC
code.  Is this right?

It does need the whitening for the reason you mentioned.

gmsk2_pkt.py uses delete_head().  I can't find this code, where is it?  The
way it's called, it almost looks its part of some standard package.  Is it?

Mike

Original Message:
-----------------
From: Eric Blossom address@hidden
Date: Thu, 1 Dec 2005 14:08:45 -0800
To: address@hidden, address@hidden
Subject: Re: [Discuss-gnuradio] (no subject)


On Thu, Dec 01, 2005 at 01:53:15PM -0500, address@hidden wrote:
> On Wed, 30 Nov 2005 15:00:34 -0800, Eric Blossom wrote:
> > The calling sequence for the gaussian filter design changed.
> > Even if ggmsk-test were fixed to use it, it doesn't work anywhere
> > nearly as good as the new code.
> 
> I would like to use the new code in gmsk2 but I can't implement the CRC32
> and the whiten/dewhiten in the microprocessor used in the transmitter. 
The
> original engineer on this project, who left the company and that I am
> replacing, selected a real poor microprocessor.

Then use CRC16.  It only requires a constant 256 byte table.
The table required for whitening only needs to be as long as your
longest message.  Shouldn't be a problem, even on a 8051.

What processor *did* he choose?  ;)

> Do you think that I can use the same basic idea of the gmsk2 framer and
> sync whithout the use of the CRC32 and whiten?

Without whitening you may get no transitions in the data (e.g., all
zeros or all ones).  This results in a single tone which has zero
information for recovering the clock.  Whitening is cheap.  I assume
you've got some flash to store code and/or data.

Eric

--------------------------------------------------------------------
mail2web - Check your email from the web at
http://mail2web.com/ .