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Smartpreamble of CC1121

Nomo
Guru 16800 points
Other Parts Discussed in Thread: CC1121, CC1200

Hello,

I have two questions for Smartpreamble of CC1121.

1. How long should I wait between SWORRST and SWOR? I think 1ms is needed.
2. How can CC1121 receive a packet without 1ms wait in eWOR mode?

I consult with cc120x_smartpreamble_rx.c in swrc274a, and the following instructions are described.
===================================
trxSpiCmdStrobe(CC120X_SWORRST);
waitUs(50);
trxSpiCmdStrobe(CC120x_SWOR);
===================================

However, for CC1121, the above instruction doesn't work (the packet can't be received), because the wait time is so short.
And then wait time is changed from 50us to 1ms, the packet can be received.

Best Regards.

Nomoto

  • 0
    TI__Guru* 85791 points

    Hi

    It is not necessary to wait 1 ms but you need to increase the delay to 62.5 us. It takes up to two clock periods (RCOSC) to reset the eWOR timer. This means that on the CC1121 this delay should be (1/32000) *2 = 62.5 us. The code example on the web is for the CC1200 which uses a 40 MHz crystal. In this case the delay does not need to be longer than 50 us.

    (Note that there is an error in the CC112x/CC120x RX Sniff Mode With SmartPreamble Design Note where it says that the delay should be two clock periods on the xosc, not the rcosc).

    Siri

  • 0 in reply to Siri
    Guru 16800 points

    Hello Siri-san,

    Thank you for your reply.
    In the CC1200 case, do you mean 40 kHz crystal not 40 MHz crystal?

    Best Regards.

    Nomoto

  • 0 in reply to Nomo
    TI__Guru* 85791 points

     

    Hi

    I am referring to the RCOSC used by the sleep timer. The RCOSC runs on fXOSC/1000. For CC1200 fXOSC is 40 MHz, for CC1121 it is 32 MHz. This means that the RCOSC runs on 40 kHz (CC1200) and 32 kHz (CC1121).

    BR

    Siri

  • 0 in reply to Siri
    Guru 16800 points

    Hello Siri-san,

     

    Thank you for your reply.

    I can understand.

     

    Best Regards.

     

    Nomoto