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CC2500 WOR Theory of Operation

Paul Groschen
Expert 2006 points

Other Parts Discussed in Thread: CC2500

I am working on a low power infrequent data transmission design using a CC2500. I am looking for an explanation of the data flow between the transmitter and receiver. Following design note DN111 the transmitter is setup to continuously transmit for the duration of EVENT0 time.  The receiver wakes up from sleep once with its RX time adjusted to be longer than the transmitter packet time. My question is when does the receiver respond to the message and when is the transmitter in RX mode? Does the transmitter turn on RX after EVENT0 time and stay in RX for the next EVENT0 time?

Regards

Paul

 

  • 0
    Intellectual 490 points

    Paul, 

    For the Receiver, if you set the Event0 to wakeup once per second, it will response once per second.  The receiver/Transmitter will go to idle mode (default setting in MCSM1) after a packet is transmitted/received.  You will then need to execute the WOR strobe to enter back into WOR mode.

    For the transmitter, if you set it to go back to idle mode, it will take ~1msec to switch and calibrate to enter into TX mode again for the next packet.  This will cause you to have to set the Receiver RX Time to be longer than 1msec to see a minimum of 2 packets from the transmitter.  Another thing with the Transmitter is that, you will need to transmit continuously for the 1 second period, as the transmitter is in sync with the Receiver WOR.  This usually causes more curent consumption on Transmitter side.

    Ben.

  • 0 in reply to Ben45875
    Expert 2006 points

    Ben,

    I am assuming a Master (TX) / Slave(RX) relationship. The transmitter is requesting data from the receiver

    For the transmitter: when does it go into receive mode? For the 1st packet at least, the transmitter and receiver are not in sync yet. Does the receiver wait until the transmitter is finished with the 1 second of transmissions before the receiver transmits? Or does the receiver send a packet as soon as it receives a packet?

    Paul

  • 0 in reply to Paul Groschen
    Intellectual 490 points

    Paul, 

    1) You can have the transmitter wait until it finishes before switching the radio to RX Mode to capture the receiver packet.  The receiver is also waiting as well.  In addition, you should set the radio on the receiver OFF so that it doesn't consume power and use the Timer interrupt to wake up after the 1 second to transmit the requested data when you know that the transmitter is in RX Mode.

    2) If you want to receiver to send a packet after it wakes up, you will need to set the transmitter in RX Mode after each send packet as the Receiver is not in sync.  Doing this, you will need to set the Receiver's RX time longer to account for this.

    Ben.

  • 0 in reply to Ben45875
    Expert 2006 points

    Thanks for the reply.

    I am trying to determine What Time period I should set Event1 for? It looks like the only requirement is: EVENT1 > XOSC start up time + PO_TIMEOUT.

    So 150usec oscillator startup + 155usec(PO_TIMEOUt) = 305usec?

    Paul

  • 0 in reply to Paul Groschen
    Intellectual 490 points

    Paul, 

    Yes, that is correct.

    Take a look at this design note: http://e2e.ti.com/support/low_power_rf/w/design_notes/dn111-current-consumption-for-a-polling-receiver.aspx

    It describes and provide some examples for setting the Event1, data rates, etc.. as it relates to current consumptions.

    Ben.