Hello all. Its been quite some time since I was on an email list.
I have been programming most of my life, everything from Assembler to
FoxPro. But I am brand new to NESC and TinyOS.
I have a question concerning the CC2420. I am using a MicaZ mote, Linux
and TOS 2.1 something?? I'm not exactly sure as I have for some reason
removed all the .svn folders from my source. But I checked it out only
about a month ago.
Anyway, I am attempting to write code that detects wireless traffic
patterns (any wireless). I am using CCA interrupts to detect when
traffic begins and ends and basically just output the time between the
CCA pin going low (channel becomes clear) and going high (channel
becomes busy).
I humbly ask the following questions:
1. What is the best way to recover data from a mote? I am getting the
data currently by means of the printf library (I post a task from within
the interrupt to do this) This is fine for me unless it causes problems
that I am unaware of (extremely slow?).
2. My code seems to be working but I added a sanity check where when an
interrupt is fired the first thing I do is check the status of the CCA
pin, and about 1% of the time (pure guesswork here) the pin indicates
the opposite status of the interrupt I just received. Is this normal? I
have posted the relevant code below.
async event void InterruptCCA.fired()
{
atomic
{
bool pin = call CCA.get();
switch(ccaState)
{
// Caught a rising edge, so we are beginning a new
whitespace period.
case NOT_CLEAR:
if (!pin) printf("STRANGENESS: CCA PIN CHANGED, BY
TIME INTERRUPT WAS CALLED!\n");
ccaState = CLEAR;
// Timestamp a new white space data structure in
the queue.
beginWhiteSpace();
// Reset the interrupt for when channel becomes
busy (pin goes low).
call InterruptCCA.enableFallingEdge();
break;
// Caught a falling edge, this indicates the end of the
whitespace period.
case CLEAR:
if (pin) printf("STRANGENESS: CCA PIN CHANGED, BY
TIME INTERRUPT WAS CALLED!\n");
ccaState = NOT_CLEAR;
// Finish the previous whitespace data structure in
the queue.
endWhiteSpace();
// Reset interrupt for when the channel becomes
clear (pin goes high).
// This will indicate the beginning of a new white
space.
call InterruptCCA.enableRisingEdge();
break;
}
}
}
Thank you all.
Ted Ward
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