AVR-Chat

At 09:08 AM 8/06/2010, you wrote:
>Not that I expect this, but say the last packet arrives first...
>Or the middle packet arrives three times. (very possible)

What information is in the packet that tells you the sequence?

If a packet can be received more than once in a particular sequence
do they have some time stamp from the source or is this done at the
receiving end? Do you discard multiple packets and keep the newest one?

Regards

John Samperi

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> What information is in the packet that tells you the sequence?

There's a byte in each that says which one it is.

> If a packet can be received more than once in a particular sequence
> do they have some time stamp from the source or is this done at the
> receiving end? Do you discard multiple packets and keep the newest one?

The source flings them out into a mesh network, so I may get multiple copies.
I can discard dupes, I just need to know when I have all the "slots" full.


Initially I was thinking that I'd do a bit array, set the unused bits
to 1, the "not arrived yet bits" to 0, and then flip them to 1 as the
packets arrive.  When the array ands to FF, then I'm done.   Seems
simple in concept, but messy so far in C.

On 6/7/2010 9:07 PM, David VanHorn wrote:
> Initially I was thinking that I'd do a bit array, set the unused bits
> to 1, the "not arrived yet bits" to 0, and then flip them to 1 as the
> packets arrive.  When the array ands to FF, then I'm done.   Seems
> simple in concept, but messy so far in C.

To set received bit

receive_fl |= 1 << pktnum;


To check all received

if( receive_fl == 0xFF) {}

Setting not used to one is a little more work but assuming that they are 
not scattered a very straightforward loop will do it.

receive_fl=0;
for( i =  first_not_rec; i < 8; i++) {
     receive_fl |= 1 << i;
     }

Obvious optimizations for known fixed receive groups left as an 
exercise.  Syntax errors and typos are to check if you are following ;)

Looks simple and clean to me.

Robert

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http://www.aeolusdevelopment.com/

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ME - "Anything we can do about lead time?  37 days seems a bit high."
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Damn!! I didn't scroll down far enough from your initial message!! Same idea
I thought of but reversed bit state!!

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of David VanHorn
Sent: 08 June 2010 08:07
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Bit fields

 

  

> What information is in the packet that tells you the sequence?

There's a byte in each that says which one it is.

> If a packet can be received more than once in a particular sequence
> do they have some time stamp from the source or is this done at the
> receiving end? Do you discard multiple packets and keep the newest one?

The source flings them out into a mesh network, so I may get multiple
copies.
I can discard dupes, I just need to know when I have all the "slots" full.

Initially I was thinking that I'd do a bit array, set the unused bits
to 1, the "not arrived yet bits" to 0, and then flip them to 1 as the
packets arrive. When the array ands to FF, then I'm done. Seems
simple in concept, but messy so far in C.



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