Re: [uracoli-devel] Frame Control Field

[Axel]

Am Mittwoch, 9. März 2011 19:19:27 schrieb Eduardo Aldaz Carroll:
> First a disclaimer, I'm a beginner with the 802.15.4 standard.


No mattter, not much IEEE knowledge is needed for uracoli, it is mostly
the frame encoding that is done in Software, all the rest is done in the 
transceivers.
>
> #define FRAME_CTRL (0x8841)
>

Here we use the fact, that AVR is a little endian device and so uint16_t fctl
is bit reversed. In Python you can quickly verify the endianess effects with 
the following lines:

python
>>> import struct
>>> map(hex,map(ord,struct.pack("<H", 0x8841)) # "<H" is little endian 16 bit
--> [0x41, 0x88]

The transceiver sends out LSB first (representation in 802.15.4)

"C"    => Memory         => On Air 
                             1    4    8    8 
0x8841 => [0x41, 0x88]   => 1000 0010 0001 0001
                             (a)  (b)  (c)  (d)

a: Frame type = data frame
b: PAN ID compression
c: short dest. address
d: short source address



Hope this helps, cheers, Axel