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

[Jan Hauer]

>  Some more details: I run the same test code on micaz (on which the
>  baudrate is 57600) and no packets were lost. I also lowered the baudrate
>  to 57600 for telosb and it also stop losing packets. I only tested with
>  low (1 packet/s) data rates from PC to the mote.

A possible explanation: on telosb UART1 clock source is SMCLK. The
source of SMCLK is DCO/4. The DCO is highly temperature dependent but
currently calibrated only once (when the node boots). When DCO
frequency changes the UART baudrate will change also and this effect
is more crucial at 115200 compared to 57600 baud (where a symbol is
twice as long).

Jan

>
>  Question for Ben: did you also notice this?
>
>
>
>  --
>  Razvan ME
>
>  >> On Sat, Apr 19, 2008 at 3:47 AM, Razvan Musaloiu-E. <razvanm at cs.jhu.edu>
>  >> wrote:
>  >>
>  >>> Hi!
>  >>>
>  >>> I just noticed that when a mote sends a lot of packets to a the PC, the
>  >>> packets from the PC to the mote doesn't go reach the user application layer
>  >>> some of the time. In the attached archive there is a test program that is
>  >>> exposing this. The mote program is sending packets back-to-back while the PC
>  >>> program (in Java) is receiving the packets and sends to the mote one packets
>  >>> each second. I run the program on telosb in the following way:
>  >>>
>  >>> (console 1)$ ./sf 9001 /dev/ttyUSB0 115200
>  >>> (console 2)$ java StressSerialTest -comm sf at localhost:9001
>  >>>
>  >>> The mote is toggling the blue led each time it receives a packet and it
>  >>> should change state each time the RX led from the USB blinks. This doesn't
>  >>> always happen: the RX led indicates a receive but the blue doesn't always
>  >>> change its state. The (console 1) also shows lines like this:
>  >>>        Note: write failed
>  >>>        Note: write failed
>  >>>        Note: write failed
>  >>>        Note: write failed
>  >>>
>  >>> Did anyone else notice this behavior?
>  >>>
>  >>> --
>  >>> Razvan ME
>  >>>
>  >>>
>  >>
>  >
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