Hi, Another question: STXON is strobed when header is loaded in TXFIFO, while the payload is loaded later. Why is there no second STXON strobe to transmit the payload?
Thanks for your patience. -Xiaohui On Mon, Dec 3, 2012 at 9:44 PM, Xiaohui Liu <[email protected]> wrote: > Hi Janos, > > I see. > > I changed the timestamping in CC2420 stack accordingly, but occasionally > wrong timestamps still pop up. My speculation is that the following corner > case is causing problem: > ____ ____ > __| |__| |_ > > As SFD pin activity shown above, a packet transmission ensues a packet > reception. The MCU does not respond to the 1st SFD rising till after the > 2nd SFD rises. After the packet is read out of RXFIFO, there is no other > packet in RXFIFO and thus the timestamp of the transmitted packet is > mistakenly assigned to the received packet. I'm reading CC2420X but haven't > found how this case is dealt with. Please give me some hint. Thanks again. > > -Xiaohui > > On Mon, Dec 3, 2012 at 5:26 PM, Janos Sallai > <[email protected]>wrote: > >> The hardware is fairly deterministic: After issuing the STXON strobe the >> SFD will be transmitted with a constant delay. It's more efficient to take >> a timestamp when issuing STXON and adjust it with a constant TX_SFD_DELAY >> than servicing an SFD interrupt. >> >> Janos >> >> >> On Mon, Dec 3, 2012 at 4:10 PM, Xiaohui Liu <[email protected]> wrote: >> >>> Hi, >>> >>> Thanks for clarifying the reception timestamping. >>> >>> Why is *TX_SFD_DELAY* accounted for during transmission, but not during >>> reception? Isn't *sfdTime* the time SFD byte has been transmitted so >>> there is no need to add *TX_SFD_DELAY*? >>> * // adjust time32 with the time elapsed since the SFD event* >>> * time -= sfdTime;* >>> * time32 -= time;* >>> * >>> * >>> * // adjust for delay between the STXON strobe and the transmission of >>> the SFD* >>> * time32 += TX_SFD_DELAY;* >>> * >>> * >>> * call PacketTimeStamp.set(msg, time32);* >>> >>> -Xiaohui >>> >>> On Mon, Dec 3, 2012 at 1:45 PM, Janos Sallai <[email protected] >>> > wrote: >>> >>>> FALSE >>> >>> >>> >>> >>> -- >>> -Xiaohui Liu >>> TelosB >>> TinyOS 2.1.2 >>> www.cs.wayne.edu/xliu/ >>> >>> >> > > > -- > -Xiaohui Liu > TelosB > TinyOS 2.1.2 > www.cs.wayne.edu/xliu/ > > -- -Xiaohui Liu TelosB TinyOS 2.1.2 www.cs.wayne.edu/xliu/
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