[Tinyos-help] Making heads or tails of TEPs113, 111, and actual code

[Jeongyeup Paek]

> while the actual source code shows it as:
> typedef nx_struct serial_header {
>     nx_am_addr_t dest;
>     nx_am_addr_t src;
>     nx_uint8_t length;
>     nx_am_group_t group;
>     nx_am_id_t type;
> } serial_header_t;
> in serial.h, which is 7 bytes.


7 bytes is correct. I heard that there has been a recent modification
to the serial packet format: added 'src' field. TEP should be updated.


> TEP111 implies that the serial header is 5 bytes (in section "3.1 
> Headers"), when, in reality, according to my experiments, it's at least 
> 7 bytes, and, most likely, 9 bytes.  Let me elaborate...

No, you should not call it 9...
that is a different story as you've mentioned below...
they are 'frame-related' stuff...

> TEP111.  I understand why it might not be mentioned there, since it's 
> frame-related and not really related to message_t.


> Notice my data starts at byte 9 (like it should based on the reasoning 
> above).  Bytes 109 and 110 seem to be the CRC.  The framing 0x7e (and 
> any escaped chars) have been removed automatically by my code.

If 'your code' removed the framing and escape chars, then
'your code' should *also* remove bytes 0,1,109,110.
That is what 'frame-related' stuff do: remove framing (start/end), 
remove framing protocol header (0,1), escape chars, CRC...
and return only 'serial_header'.

> Does all this sound reasonable?

Yes...

  -jpaek

> Regards,
> Kurt
> 
> 
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-- 
Jeongyeup Paek
Ph.D. student
Embedded Networks Laboratory
Department of Computer Science
University of Southern California
http://enl.usc.edu/~jpaek