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CC1200: SmartRfStudio 7 (V2.5.1) doesn't automatically adjust all registers according to the RF parameters in Expert Mode for CC1200

Jianyi Bao
Expert 2220 points
Part Number: CC1200
Other Parts Discussed in Thread: CC110L, , CC1101

I want to communicate CC1200 with CC110L. Some important settings for CC110L is as following:

  1. Deviation = 126.953125

  2. Base frequency = 432.999817

  3. RX filter BW = 541.666667

  4. CRC enable = true

  5. Modulation format = 2-GFSK

  6. Preamble count = 4

  7. Carrier frequency = 432.999817

  8. Sync word qualifier mode = 30/32 sync word bits detected

  9. Data rate = 249.939

     

    When I use SmartRfStudio V2.5.1 to export the register settings for CC1200, I found it doesn’t have a default setting for 433M and 250k bps 2-GFSK. The following is the list of default settings:

     

    So I start with the first one (1.2kbps). I can see value for register “AGC_CFG0” is 0x87. And then change the RF parameters as following, and I can see “AGC_CFG0” is still 0x87.

     

    If I start with 100kbps, 2-GFSK, “AGC_CFG0” is 0x80. After I adjust the settings to the same as the picture above, it is still 0x80.

    So “AGC_CFG0” is actually not tuned for 250kbps automatically by the software when I change the bit rate. It remains the value as when I select a default setting.

    Some other registers has the same issue.

    So my question is:

  1. Can SmartRfStudio tuned all the necessary registers to optimal settings when I change my settings automatically?

  2. If not, what should I do to get optimal register values for my setting (250kbps, 2GFSK, performance mode)

  • 0
    Expert 2220 points

    Sorry, two pictures are lost when pasted from word.

  • 0 in reply to Jianyi Bao
    TI__Guru**** 317180 points

    CC1200_250kbps_e2e.xlsxIf the datarate you need is not available in SmartRF Studio you should start from the setting that is closest when it comes to Rx filter bandwidth.

    Attached is some settings for 250 kbps for CC1200 that should be good. Note that to communicate with CC1101 you need to change the sync word. 

  • 0 in reply to TER
    Expert 2220 points
    Hi, TER,
    Besides 250kbps, is the register value for 433M, 127 dev and 2-GFSK, which is the parameter I want?
    And how do you get the register value? If I use smartRfStudio and start from "434M 100kbps, 2GFSK, ETSI Standard", and change RF parameter to the values I want, I can see the register values are not exactly the same as those you provide. So I wonder what steps should be done further.
    Thanks
  • 0 in reply to Jianyi Bao
    TI__Guru**** 317180 points
    I wrote that you have to start from the setting that has a Rx Bw closest to what you need, the 100 kbps setting uses a much lower Rx Bw than a 250 kbps setting needs.

    433 MHz: You have to change the freq word since the settings I sent was tested on 868 MHz. You also need to change FS_CFG to get the correct divider. Use SmartRF Studio to calculate the correct frequency word.
    Deviation/ modulation: Use SmartRF Studio to calculate the correct deviation settings for your need, also the modulation setting.

    All settings will never be equal, you should compare the ones that are different to get a feeling of if the difference is important or not. Example: The deviation setting can freely be set by the user (to some degree at least) as long as the signal fits in the Rx Bw. The FS_* registers are don't touch and changes should not be made without knowing the effects.
  • 0 in reply to TER
    Expert 2220 points

    Hi, TER,
     Thanks for you answers.
     
     I had though by using SmartRfStudio I could get the register values without knowing the details of the chip registers thoroughly. Now it seems not true. I can understand some registers easily, such as PKT_CFG*. But some others, such as AGC_CFG*, are much more difficult for me.
     
     I think SmartRfStudio should provides more default settings for different configuration for CC1200, like for CC1101/CC110L, where there are so many default settings for different data rates.
     
     I still have difficult in selecting the closest "Rx BW". 100k uses 208kHz, and "500ksps, 2FSK, ETSI Standard (434Mhz)" uses 833kHz. As I should use 555k, shall I select the latter to start? Since I use 2GFSK, I would first not consider 4GFSK or OOK. Thank you.
     
     

  • 0 in reply to Jianyi Bao
    TI__Guru**** 317180 points
    Try the later. I thought we had done some tests with the same bandwidth you are using but couldn't find one.