Hi, Thanks for your reply.
Doesn't the Alarm interface run at interrupt level, and AMSenderC$AMSend$send at sync level? The issue is that there is potentially long and non-deterministic delay when going from interrupt level (i.e., async) to sync level. On Mon, Jul 2, 2012 at 11:02 PM, Eric Decker <[email protected]> wrote: > sync will always have some jitter (unless you aren't really doing anything > else besides the one task). > > so you will have to so the TDMA slotting at interrupt level and kick the > transmitter stuff at sync level. > > > On Mon, Jul 2, 2012 at 7:51 PM, Xiaohui Liu <[email protected]> wrote: > >> Hi everyone, >> >> I'm implementing a TDMA protocol, in which each slot lasts 10 ms. At the >> beginning of each slot, a node sends a packet (using >> AMSenderC$AMSend$send) if it captures the channel through some contention >> resolution algorithm. For the protocol to function, each slot duration has >> to be as close to 10 ms as possible. I tried the following two methods: >> >> 1. setup a periodic Timer with period 10 ms. But Timer interface >> works in synchronous context and the interval between two consecutive >> firing can be much larger than 10 ms as also mentioned in this >> thread<http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2007-May/024953.html> >> . >> 2. setup an Alarm to fire every 10 ms. The timing is precise. >> However, Alarm$fired event is asynchronous and AMSenderC$AMSend$send is >> synchronous and thus cannot be called directly from Alarm$fired. If a task >> is post in in Alarm$fired to call AMSenderC$AMSend$send indirectly, it >> suffers from the same issue as Timer interface does. >> >> FTSP is also used in the protocol, which transmits >> via AMSenderC$AMSend$send. That's why packet transmission is >> through AMSenderC$AMSend$send in my TDMA protocol, to be compatible with >> FTSP. >> >> If you have any suggestion, please do not hesitate to share. Your help >> would be sincerely appreciated. >> >> -- Cheers >> -Xiaohui Liu >> > > > > -- > Eric B. Decker > Senior (over 50 :-) Researcher > > > -- -Xiaohui Liu
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