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CC1200: Clock sync over RF

Prodigy 225 points
IceCube

Part Number: CC1200

Hi,

I need to sync clock from a master over RF with an accuracy of +/- 1uS each 40mS. I also need to send a few bytes each time.

I was thinking to use a CC1200 in 1250kbps mode and use the low jitter data output for sync. 

Range has to be 10 meters in direct line of sight.

Would this be possible?

Regards,

Rolf

Prodigy 225 points
IceCube
  • Guru 164280 points
    TER
    What do you define as "low jitter data output" in this case?

    It will be some delays both on the Tx and Rx side, which clocks do you want to use and how are you going to sync them?

    You can also look into CC13xx, see dev.ti.com/.../time-synchronization.html
  • Prodigy 225 points
    IceCube

    In reply to TER:

    Thank you for your answer.

    I do not necessary need to sync time, just receiving a pulse every 40ms with 1us jitter max is sufficient. The syncing is done inside a microcontroller. I already did some experiments with the CC1200 and used the transparent data mode (low jitter serial data output as in the attached picture).

    I notice a (constant) delay of 11.5us between transmitter and receiver. Jitter is about +/- 0.5uS. The constant delay is not much of a problem but I am wondering what's the cause of this. The jitter is just inside the margin, however is there anything I can do to minimize it further?

    See attached scope picture for details. Blue line is transparent TX input into CC1200 #1 and yellow line is transparent RX output from CC1200 #2.

    Thanks in advance!

    Rolf

  • Guru 164280 points
    TER

    In reply to IceCube:

    The transparent mode has a fairly large jitter due to limited time resolution internally. If my memory serve me right the jitter could be up to 1/8 of the programmed datarate. Or more correct 1/(8*datarate).

    Have you considered using the sync found signal (see table 10 in the UserGuide) as the signal you sync on? This signal is much more accurate (low jitter) that the transparent output.
  • Prodigy 225 points
    IceCube

    In reply to TER:

    Finally did some testing. The sync found signal is easy to use and I got +/- 250nS jitter @ 500Ksps. Selecting the CC1200 was a right choice :-)

    Thanks for your help!

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