[Tinyos-help] (no subject)

[Branislav Kusy]

> Basically, I just attached TimeSyncP component without any modification. 
> And it works very well without any interfere from our program. But since 
> our program is using UART0, which is sharing resource with CC2420 radio 
> stack, global time is not accurate after our program starts. I think the 
> problems are  
> 
> 1.       Many time beacon messages are dropped.
> 
> 2.       Even if a beacon message has arrived, it takes time for 
> signaling through Receive interface and the time is vary depends on 
> mote’s condition. (It may transmitting data through UART0)
> 
> 3.       Interval of beacon message(broadcasting) is not exactly same, 
> depends on mote’s condition.(same reason with above)
could you log messages and send it to me? assuming that you use 
T2/apps/tests/TestFtsp, logging the output from the FtspDataLogger.java 
for each motes would be fine (alternatively, you can log the struct 
test_ftsp_msg_t defined in TestFtsp.h with your favorite method). also, 
can you describe your setup more precisely (how many motes, how many hops)?

as for number 2., ftsp timestamps in the MAC layer, so no matter how 
long the delay of the receive event is, you'll always get a correct 
timestamp. variances in beacon message periods (even up to a few times 
the beacon period) should not be a problem.

> I used PacketLink layer to prevent drop of beacon message, but it may 
> causes inaccuracy of global time since it will try several time for 
> sending and it takes time.
the timestamping is done in the MAC layer, so this would definitely be a 
problem if your hardware supported link layer retransmissions. but i 
think that PacketLayer actually sits above MAC in tinyos, so this should 
not be a problem.

brano