sergio masci ha scritto:
>> I wanted to place a question for you all. I can't see a "frame id" i.e. 
>> a counter in the above protocol: I found it mandatory to deal with 
>> repeated packets and retransmission.
>>
>> What do you think about this?
> 
> Yes I also belive it should be mandatory. For one thing it helps 
> acknowledgement of packets that arrive out of sequence.

Yep, I've been about this in the night, and actually Gerhard reply, 
saying that it can be placed at a higher level in the Protocol, makes 
sense. In my case it's not like this, at the moment. of course the 
overall result is the same, just a matter of cleanness of protocol and 
level.


> For multi master collision detection, have you considered sending back the 
> CRC as part of the ACK. If two masters have both sent packets and have not 
> seen a collision and a slave has also seen a valid packet from one of the 
> masters, sending back the CRC will inform (probably) one of the masters 
> that there was a collision. Maybe include the ID of the node that the ACK 
> is intended for?

Not sure what you mean here , Sergio.
In my case, the ACK is a message on its own and not barely a flag in the 
Frame. If 2 masters send a packet to the same slave, there will be 
either a collision or the slave may receive only one of them and miss 
the other. In the 1st case, both masters will retry (maybe after a 
random delay - though often the devices will send packets after a human 
event, say a button press, which is random inherently), with the same 
FrameID and will wait for ACK again; in the 2nd case, the 1st master 
will be ok and the second will retry and, then, get a reply.

So, yes, the replied ACK includes the destination ID (the master who 
sent the command in first place).


Dario
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