Hi,
I'm working with telosb and I'm trying to find a solution to estimate
the time taken by some operation accurately (micro second). I first
tried the TimerMicro but as i found after in the mailing list (here
http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2007-May/024953.html)
I understood that it was not a good solution and followed the Cory's
advice: trying with a Counter<TMicro,uint32_t> and then Counter<TMicro,
uint16_t>. I made a very simple test program: an infinite loop in the
Boot.booted event which calculate dt between 2 loops and generate a 0 or
1 on one of the pins of the mote if dt >= INTERVAL. Then i looked at the
signal on an oscilloscope and measured the period of the "wave". I found
that i can't have it < 16 us, ie with values of INTERVAL between 1 and
16-18 the period is the same. I wondered if it was normal since my
program is only doing this. I have also another question, I got jitter
in my signal and i would like to understand why, i thought that
gpio.set, gpio.clr and counter.get were done in constant time.
here is my loop:
event void Boot.booted()
{
uint16_t t;
uint16_t t0 = call Counter0.get();
call outIO.makeOutput();
while(TRUE)
{
t = call Counter0.get();
if(t-t0 >= INTERVAL)
{
if( up )
call outIO.set();
else
call outIO.clr();
up = !up;
t0 = t ;
}
}
}
Maybe I made something wrong. Can anyone help me with it?
Thanks
Nicolas
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