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CC1311R3: Sync threshold

no_more_wires
Expert 1520 points
Part Number: CC1311R3
Other Parts Discussed in Thread: WMBUS

Tool/software:

Hi,

I have trouble with too many false sync in my CC1311R.

I see that it is possible to control the sync threshold.

Ref :  //www.ti.com/lit/an/swra682/swra682.pdf?ts=1760355646360&ref_url=https%253A%252F%252Fwx.mail.qq.com%252F

I thought CC1311 was register compatible with CC1312, and tried to to HW_REG_OVERRIDE(0x5114,0xYYZZ) But saw no/little difference

Q1: IS it register 0x5114 that I need to write to for CC1311 as well?

Q2: The description on how to tune the sync threshold is limited. YY has been set to 0x19, 0x1A, 0x30 and 0x70.

        What does YY mean and how is sync correlation calculated to be compared with this number.
        I want to understand if should be tuning 0x18-0x1C range or the 0x18-0xFF range.

I have 16 bits sync and this is given by the legacy system

Regrads

No-more-wires

  • 0
    TI__Guru* 86731 points

    Hi

    The sync threshold is set through override HW_REG_OVERRIDE(0x5114,0xYYZZ) on the CC1311.

    If you set sync length to be 16 bits, the default threshold is set to:

    ((30 * 16)/32) + 9 = 24 (0x18).

    The valid range for the threshold is 0x00 to 0x7F

    If you test with Studio you will see that if you select 16 bits sync word and set the threshold to 0x00 (HW_REG_OVERRIDE(0x5114,0x0000)) you will receive a lot of false packets when setting the device in RX (without having a TX).

    On the other side, if you set it to HW_REG_OVERRIDE(0x5114,0x7F7F) you will not receive any false packets, or even real packets if you start your transmitter, as the threshold is too strict.

    If you want to change the threshold, you should start by the default of 0x18 for the 16 bits sync, and then modify in steps of 1 (higher value means stricter threshold)

    BR

    Siri

  • 0 in reply to Siri
    Expert 1520 points

     Hi Siri, 

    I understand your technical description. 

    My problem is that I set the override to 7F and I still receive packets and false sync...
    I just tripple checked that I use the correct overrides struct.

    Does the register depend on the patch I am running or are the register mapping independent of that?

  • 0 in reply to no_more_wires
    TI__Guru* 86731 points

    What PHY and patches are you using?

    The sync threshold can for example not be adjusted like this when using Simplelink Long Range Mode, as this mode does not use a "normal" sync word.

    Siri

  • 0 in reply to Siri
    Expert 1520 points
    wireless mbus - rf_patch_mce_wmbus_ctmode.h
  • 0 in reply to no_more_wires
    TI__Guru* 86731 points

    when using the patch for wmbus ct mode, the threshold is hardcoded in the patch, and cannot be modified.

    BR

    Siri

  • 0 in reply to Siri
    Expert 1520 points

    OK. It just seemed strange that SmartRfstudio recommend for this use case this override: 

    // Set correlator threshold

    HW_REG_OVERRIDE(0x5114,0x197F),

    What you say is that this info from SmartRFstudio is "misleading" as the override will be ignored in RFcore?

  • +1 in reply to no_more_wires
    TI__Guru* 86731 points

    The correlators are used differently when using the patch, and are used to distinguish between C more and T mode packets.

    You should NOT change this register settings when using the patch.

    BR

    Siri