I"ve been working through the T2 tutorial 3, and use AMsend instead of
Packet just to self teach,
and hit a cryptic C part I want to ask for alternative ways to write.
It comes up using
the Packet or AMSend interfaces. If you use Packet.getPayLoad(&pkt,
NULL) or
AMSend.getPayLoad(&pkt) to find out the address of the next packet, you
can use
a line from the tutorial and it compiles, but is so opaque to me I want
to find other ways to write it.
BlinkToRadioMsg* btrpkt = (BlinkToRadioMsg*) (call
AMSend.getPayload(&pkt));
//cast result of .getPayload to pointer of nx_struct BlinkToRadioMsg*
btrpkt->nodeid = TOS_NODEID; // stuff data in struct member
btrpkt->counter = counter; // stuff data in struct member
where the header file includes this struct definition:
typedef nx_struct BlinkToRadioMsg {
nx_uint16_t nodeid;
nx_uint16_t counter;
} BlinkToRadioMsg;
Is there any way to write the top line more like:
BlinkToRadioMsg* btrpkt ; // declare type of btrpkt is address of struct
btrpkt = (call AMSend.getPayload(&pkt));
or maybe just:
BlinkToRadioMsg* btrpkt ; // declare type of btrpkt variable
call AMSend.getPayload(&btrpkt)
What is the meaning of
(BlinkToRadioMsg*) (call AMSend.getPayload(&pkt));
in the top line? Is this the syntax for coercing to type BlinkToRadioMsg*?
Where in the docs is this syntax defined?
It's not like K&R C...where
you would declare *btrpkt to get a pointer you could use as btrpkt->nodeid
John Griessen
Ecosensory
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