[Tinyos-help] Lost serial packets?

[David]

Hi list.

I've been working with Razvan ME's Python module for communicating
with motes over serial: tools/tinyos/misc/tos.py

One thing I've noticed is that packets sent over serial can disappear
(not get acked by the mote), so the module has to retry packet writes
sometimes. Why do serial packets sometimes dissapear?

I've also noticed that more sent packets get lost if the mote app is
moderately busy. eg, in tests with tos-deluge, the data rate can drop
from 1300 bytes/s to 700 bytes/s if the mote is eg: in a loop where it
 communicates with another motes over radio, sends + receives 10
packets a second, and does some basic processing.

I've checked, this is caused by failed acks, rather than (or not only)
the mote just receiving slower because it's busy.

Is this normal? Why doesn't the mote hardware buffer incoming serial
packets for a bit longer, until the mote app has time to read the
data? tos.py does wait for 0.2 seconds for an ack, which should be
more than enough time for write acks (I've tried longer waits and get
the same problem).

Any ideas?

David.