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

[Vlado Handziski]

The msp430 has separate shifter and character buffer, so the time window is
about 1.5-1.7 times larger.  And I believe Ben has tested that no overflows
at the bottom-part of the ISR are causing this.

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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