hi, I did some measurements recently. I quantified the time taken by the different components. Here are my results:
before Amsend.send() statement 64420 Send.send() 64426 send() 64427 AcquireSpiresource() 64431 before loadtxfifo() statement 64432 Loadtxfifo() 64433 before TXFIFO.write() statement 64440 after TXFIFO.write() statement 64446 TXFIFO.writedone() 64519 AttemptSend() 64521 CaptureSFD.capture() 64655 ReleaseSpiresources() 64538 after loadtxfifo() statement 64447 after Amsend.send statement 64448 Amsend.Senddone() 64662 All time values are based on 32Khz timer. CCA has been disabled. Also, DMA has been enabled. This is for 100 Byte packets on telosb platform. Tx time : 135 ticks => 4.2 msec Spi copy time without s/w overheads: 73 ticks => ~2.5 msec Hope this helps. I would like to know how you are measuring the time values. If you are using printf's(like i did a few days back), then the values are likely blown up. > Hi > > Does it happen in every packet transmission? > If no, maybe some packets are retransmitted by PacketLink Layer? > > 2011/3/28 ½²¨J®p <[email protected]> > >> Dear all, >> >> >> We have a high-data-rate application and we need to decrease the >> transmission delay (between send.send and send.sendDone). >> >> The payload of our packet is 80 bytes. ( Total packet size is about 100 >> bytes in Tinyos ) >> >> We've adjusted the initial backoff time defined in CC2420csmaP.nc to the >> range of 10~60 ticks (under 32khz clock) >> >> The above two added is about 100*8/250(kbits/sec) + 35/32768 = 4.27ms >> >> But when we measure the time between send.send and send.sendDone, the >> result is 7.82ms, much bigger than 4.27ms >> >> Even though we take the congestion backoff time into account( 10~80 >> ticks >> ----> 45/32768 = 1.37ms ), the result is still less 7.82ms >> >> But the inteval between our testing data packest is 3 seconds, the >> congestion backoff time shouldn't exist. >> >> Our application is broadcast, so we don't consider ACK wait time. >> >> Does anyone know why the larger transmission delay in our experiment? >> >> >> We also record the time when the packet is send out ( by the SFD >> interrupt >> ), the time between this SFD time and send.sendDone is about 1.99ms >> >> What confuse us is this time is much less than the data transmission >> needed >> (4.27ms), does anyone know why? >> >> >> Many thanks!! >> >> >> Best regards, >> >> >> Sean >> >> _______________________________________________ >> Tinyos-help mailing list >> [email protected] >> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >> > > > > -- > Pozdrawiam, > Damian Rusinek. > _______________________________________________ > Tinyos-help mailing list > [email protected] > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
