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Original question:

CC2642R: CC2642R

CC2642R: Frequency deviation setting for CC2642R

Lumina Gui
Expert 2635 points
Part Number: CC2642R

Hi Sir,

During the production process of our BLE products, we found that the frequency deviation of the board that we produced is different from the sample board. The frequency deviation of the produced board have exceeded 200KHz.  For some reasons, we cannot change the software. So I want to know if TI has provide some tools that can write the frequency offset configuration to the chip first, and then burn the program without changing the software.

According to my experience, if the frequency offset is more than 200KHz, there should be a connection failure problem, but actually the product works well. So I want to know if there is a problem with my testing method. My testing method is as follows:

1) Testing method one

The configuration of the code is as follows:

Set the configuration information of the fixed frequency tool, the program in the chip is deleted at this time.

2) Testing method two

The configuration of the code is as follows:

Set the configuration information of the fixed frequency tool, the program in the chip is deleted at this time.

  • 0
    TI__Mastermind 30059 points

    Hello,

    I have assigned an expert to comment on this query.

    Regards,

    Jan

  • 0
    TI__Genius 15590 points

    Hi Lumina,

    Technically yes, you should be able to write directly to the register to set the cap array tuning value without having to modify the software. However, 200kHz seems way off base. I believe the cap array can only correct up to ~65kHz. 

    For information on tuning the cap array, see section 6.4 of SWRA640 

    Thanks,

    Alexis

  • 0
    Expert 2140 points

    The recommended alternative here is to update the CCFG with the appropriate offset for your design and build a new SW image. If that for some reason is not possible you have 2 options:

    1) After programming the SW in production you add a second step which writes to the appropriate CCFG fields before locking the flash. This will require an update to your production programming process, but you do not need to change your SW image.

    2) You add external load capacitors to your PCBA. This only works if your frequency offset is positive. 

    200 kHz, or 80 ppm, offset may be within what the cap-array can pull in, it depends a bit on the actual crystal used. The offset is outside the Bluetooth RF-PHY specification, but not that much so I am not surprised you still are able to communicate with your board. It will most likely not work reliably over operating conditions and for all Bluetooth devices though. 

    The document Alexis link to give good information about how to tune the crystal configuration properly. You should also make sure that the crystal you are using are within the requirements in the CC2642R datasheet.