thank you David. I misunderstood the datasheet information regarding the CCA modes. But it is possible, not during the transmission, to get the rssi data, no matter if the node is receiving or not a message? I just need to monitor the environment, but I'm not sure if in RxMode the receiver measures the RSSI value even if a preamble is not detected. Do you know if it does and the rate of RSSI sampling?
thanks a lot again! On 6/19/07, David Moss <[EMAIL PROTECTED]> wrote:
Actually, you have an option to transmit without CCA. At the hardware level, there are two command strobes to transmit the contents of the TXFIFO: STXON and STXONCCA. If you simply toggle STXON instead of STXONCCA, then your packet gets transmitted no matter who else is transmitting. There is one other software driver issue to overcome in TinyOS though – the radio stack driver does its own backoff and CCA checking by default. You'll need to disable this, probably through MacControl or CsmaControl or something.. I forget what it is in 1.x. -David ------------------------------ *From:* roberto pagliari [mailto:[EMAIL PROTECTED] *Sent:* Tuesday, June 19, 2007 4:20 PM *To:* David Moss *Cc:* [email protected] *Subject:* Re: [Tinyos-help] about CC2420 right, I just remembered that point in the cc2420 datasheet. I have a last question: the transmission of a packet is performed if the RSSI value is greater than a certain threshold, the CCA. The 3 CCA modes are 0 reserved 1 clear channel when received energy is below threshold 2 clear channel when not receiving valid IEEE data 3 clear channel when not receiving valid IEEE data and below threshold I guess the CCA value is a 8 bit unsigned integer 2 complement, so if I need to transmit a packet, regardless of other transmitting nod I should set the CCA value to its minimum, lilke -128dBm, or 0xFF. I know during the reception of a packet the RSSI is averaged over 8 symbols after the SFD has been detected. During the transmission how does is it calculated? Can I read it just using the command call function c.. HPLCC2420.read(RSSI_REG)? On 6/19/07, *David Moss* <[EMAIL PROTECTED]> wrote: The default mode for the radio is Rx mode – after it transmits a packet, it automatically switches back to Rx on the hardware. If you attempt to transmit using STXON without clear channel assessments, then your radio will not only **not** receive the other transmitter's packet, but it will cause channel interference that will prevent all other motes in the area from receiving that packet. That's the point of backoffs and CCA (clear channel assessment) – determine if the channel is clear before attempting a transmission. -David ------------------------------ *From:* [EMAIL PROTECTED] [mailto: [EMAIL PROTECTED] *On Behalf Of *roberto pagliari *Sent:* Tuesday, June 19, 2007 3:24 PM *To:* [email protected] *Subject:* [Tinyos-help] about CC2420 hi all, within RadioControlM I can see CC2420Control.RxMode(), but, after a packet has been sent I cant find any call to CC2420.RxMode() or SXON oscillator. where is it done? the second question is: once the transmitter oscillator STXON has been enabled, if an incoming message arrives, will it be lost? thank you
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