Hello again,
I defined a new CC2420 Packet-Headerformat and now I'm trying to use
the message_t that's handed
down from "unique send" in CC2420ActiveMessageP.nc and create a new
radiopacket with the original payload, but new header. I included the
new headerformat in the union platform_message.h.
The way I understand TEP 111, the next step would be to create a
packet interface for my new header. Is this correct? Or can I acces
those fields directly in CC2420ActiveMessageP.nc for simplicity?
To this effect I tried to understand what the following command from
CC2420PacketP.nc does:
/***************** CC2420PacketBody Commands ****************/
async command cc2420_header_t * ONE CC2420PacketBody.getHeader(
message_t* ONE msg ) {
return TCAST(cc2420_header_t* ONE, (uint8_t *)msg +
offsetof(message_t, data) - sizeof( cc2420_header_t ));
}
Could someone please explain? What does ONE mean, what happens here? I
believe this is some pointer-arithmetic to find the beginning of the
header in the platform_message-Union which is right-justified to the
data, but I'm not sure.
Lastly how can I distinguish between headerformats when passing the
new packet to CC2420CsmaP??
Thank you
Tobias
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