[Tinyos-devel] lost packets from PC to the mote

[Vlado Handziski]

I was referring to your 43us figure for full-duplex. Anyhow, the fact
remains that according to what we know until now, it is very probable that
this is some problem higher in the stack.

Vlado

On Mon, Apr 21, 2008 at 9:55 PM, Andreas Koepke <koepke at tkn.tu-berlin.de>
wrote:

> Vlado Handziski:
>
> > The msp430 has separate shifter and character buffer, so the time window
> > is
> > about 1.5-1.7 times larger.
> >
>
> Wrong, see queueing theory.
>
> > And I believe Ben has tested that no overflows
>
> > at the bottom-part of the ISR are causing this.
> >
>
> But long atomic blocks elsewhere may cause it.
>
>
>  Vlado
> >
> > On Mon, Apr 21, 2008 at 9:17 PM, Andreas Koepke <koepke at tkn.tu-berlin.de
> > >
> > wrote:
> >
> >  Correct, now for a little math: At 115200 Bit/s the uC has 86us to
> > > > > process each byte.
> > > > >
> > > > 115200 bits = 14400 bytes and 1/14400 is about 7e-05. So the MCU has
> > > > around 70us to deal with each byte.
> > > >
> > > Don't forget the start and the stop bit ;-)
> > >
> > >  If both directions are used, this drops to 43us. Scheduling a timer
> > > > > takes about this much in T2. So if the node happens to do
> > > > > something
> > > > > else than mere byte crunching, packets may be lost.
> > > > >
> > > > This situation should be indicated by some overflow register from
> > > > MSP420, right?
> > > >
> > > The uC can signal this, but the default configuration in T2 prevents
> > > this. So to check this, change the default configuration for the
> > > serial
> > > interface and modify the interrupt handler (you have to check the
> > > flags
> > > immediately before reading the byte).
> > >
> > > Best, Andreas
> > >
> > >
> > > _______________________________________________
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> > > Tinyos-devel at millennium.berkeley.edu
> > >
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> > >
> > >
> > >
> > >
> >
>
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