[aprssig] Question about 'H-bit' handling and WIDEn-N paths

[Robert Bruninga]

For WIDEn-N digipeating the "has-been-digipeated bit is not
set until WIDEn-0.  THen it is set.  

de Wb4APR, Bob


>>> washer at trlp.com 1/28/05 12:01:16 AM >>>

Thanks for the response. I was beginning to think no one knew what I
was referring to.

You say the "first wide" will have the H-bit set. My (possibly
mistaken) understanding of  WIDE3-3 path is that there is only ONE path
"slot" taken up, and each subsequent wide digi will just re-write that
one entry with a WIDE3-2, WIDE3-1 etc. So there's only the one H-bit to
play with.

That's where my concern is.. If you set the H-bit of that one,
subsequent digi's will just ignore the remaining "hops".

Where am I headed? I'm writing my own digi stack for a small
microcontroller to make an inexpensive digi, and I want to get the
"details" correct.

 - jim


On Thu, 27 Jan 2005 20:36:30 -0500
"John Langtry, VE3NEC" <ve3nec at sympatico.ca> wrote:

> Hi Jim,
> 
> Well, :) "forever" is not really true, at some point
> in bouncing from machine to machine, noise or QRM will
> eventually damage the I-frame, and with the CRC now
> wrong, the issued frame dies in the bounces.
> 
> Now it's been years since I played with the Layer 1
> code (not connected I-frames), but the way this should
> work, is that the transmitting station (WIDE3-3 to use
> your example) has all the H (has been repeated) bits
> unset.
> 
> When the frame hits the first N-N digi, it will take
> this and set the "H" of the first wide and hopefully
> replace the "generic" with the call sign of the machine;
> In either case the first WIDE, will have the H bit set,
> but the remaining two "WIDES" will be unset. (In this case,
> there is even more logic in there to decrement the WIDEN-N
> value.)
> 
> I'm not clear where you're headed with this one, and if
> you could give us more details, I'm sure there are many
> on the SIG that would be glad to help.
> 
> vy 73 de John VE3NEC
>  905-877-7886
>  IRLP node 2200
> 
> 
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> 

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