[Tinyos-help] Message Formats for Basestation

[Mr. Jonathan A. Gomez]

(Sorry for sending it to you again, and not to the list.  I wasn't attending to the return 
address!)

Thank you for the prompt response!

I'd like to make sure I understood properly, and I have some further questions.


> There are two separate forms of dispatch at play here, which is  
> probably the source of the confusion. AM ids specify the format of  
> the AM packet payload, while serial ids specify the format of the 
> AM packet.


Suppose this were the packet being sent over serial:

7e 44 01 00 ff ff 04 22 06 00 00 01 00 95 91 7e

Then the 44 is the serial protocol type, indicating a request for acknowledgment, the leftmost 
instance of 00 is the id of the format of the AM packet, and the 06 is the am_id_t payload 
format identifier?  This payload format identifier is also the "AM packet type" you mention 
below?

> Applications define AM handlers. That is, they define which AM 
> packet types they receive and send by wiring to particular AM ids. 
> The AM id therefore specifies what the format of the AM payload is. 

Makes sense.  I'd like to know more about how BaseStation does this, since that is the 
application in which I vest a particular interest?  

Does BaseStation ever filter out packets based on am_id_t, that is, the payload format, or does 
it merely pass them all on, no matter which ids are employed?  This latter seems to make the 
most intuitive sense.

Also, I'm looking into the code, but I'd like to ask too, if I may:  Does the 
SerialActiveMessage mechanism always send platform independent messages?  And it is always 
capable of receiving them?

[SNIP]

> This additional layer of dispatch exists to remove the TinyOS 1.x  
> problem of having platform-specific serial packet formats. The  
> default packet format, which is platform independent, is a basic AM  
> packet. But if you want to send/receive platform-specific packets  
> (e.g., see all the fields of a CC2420-specific AM packet), you can  
> still do so.

Hmmm... Depending again on the apps, or is it more transparent?


Thanks,

-- Jon.