Hi Razvan, Thank you for your reply. Yes, I originally thought that CC2420TransmitP would make a hard copy of the message_t structure into its local variable and issue the strobe later on. However, the only local variable in CC2420TransmitP is a message_t* pointer. I actually trace all the way down to CC2420Fifo -> CC2420SpiC -> HplCC2420SpiC -> Msp430NoDmaSpiC, which actually implements SpiPacket.send(message_t* ...), it's all passing pointers. Am I following the wrong data path or the hard copy actually takes place elsewhere? Thank you.
Best regards, -- Wenjie Zeng On Wed, Jan 20, 2010 at 10:20 PM, Razvan Musaloiu-E. <[email protected]>wrote: > Hi! > > > On Wed, 20 Jan 2010, Wenjie Zeng wrote: > > Hi, >> >> I read in the RI-MAC paper that by preloading the message into the TXFIFO >> buffer, we can accelerate the Send.send process. I am assuming that >> somewhere down the radio stack, we need to copy a message_t structure, >> which >> is somewhat time-consuming, rather than simply copying copying message_t* >> pointer along. Is this true? >> > > No. :-) To send a packet using CC2420 the packet first needs to be loaded > in the TXFIFO, and then a STXON or STXONCCA strobe command needs to be > issued. The send strobe can be issued much later than the actual loading. > > > I asked because, through tracing into the CC2420 radio stack, I see >> nothing >> beyond pointer copies. I am trying to push the limit of the efficiency of >> my >> protocol, so if such preloading can be done, could someone please tell me >> which file I should look at? Thank you. >> >> > I think the place you need to look is CC2420TransmitP.nc from > tos/chips/cc2420/transmit. > > I highly recommend the CC2420 datasheet: > http://focus.ti.com/lit/ds/symlink/cc2420.pdf > > -- > Razvan ME >
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