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CCS/CC1310: CC1310 Gain Checking when using IQ Sample Patch

Jianlin Zhou
Expert 1230 points
Part Number: CC1310

Tool/software: Code Composer Studio

Hello Expert, 

I'm working on my own custom CC1310 PCB board  which has one CC1310 working as transmitter and one as receiver. I build my receiver firmware based on your IQ sample patch example and my transmitter is working based on the continuous Tx example.

1. Could you please tell me that if  there is a way to check ot tone my receiver gain during recording I/Q samples?

2. I recorded some I/Q samples and do FFT for my I/Q recording. I found that my I/Q sample frequency is not stable which drifts. My symbol rate  is set as the following:

.modulation.deviation = 0x4,
.symbolRate.preScale = 0xF,
.symbolRate.rateWord = 0x106, //0x106 -- 400
.rxBw = 0x20,

Could you also please tell me why the I/Q sample rate is different for each recording? How could I fix my I/Q signal frequency?

E.g: Recorded I sample:

Thanks,

Jianlin

  • 0
    TI__Mastermind 21280 points

    Hi,

    Sorry for late reply.

    You can try to read the RF front end gain by accessing 8 LSBs of the register at physical address 0x40046080.

     The gain is in dB.

  • 0 in reply to FI
    Expert 1230 points

    Hello FI,

    Thanks for your reply.

    1.Will this gain be automatically adjust during receiving? Can I overwrite this register to change my receiver gain?

    2. Could you please take a look at my second question about I/Q sample sample rate?

    Thanks,

    Jianlin

  • 0 in reply to Jianlin Zhou
    TI__Mastermind 21280 points

    Hi,

    The gain will not change once sync is found and should remain the same during reception. You can also write to this register.

    I am looking into the 2nd question and will get back soon.

    Thanks,

  • 0 in reply to FI
    Expert 1230 points

    Hello FI,

    Thank you for your reply.

    My transmitter is transmitting unmodulated continuous wave and I'm getting my I/Q samples on my receiver. Could you please tell me how does my receiver find sync when using I/Q sample patch? 

    Best,

    Jianlin

  • 0 in reply to Jianlin Zhou
    TI__Mastermind 21280 points

    Hi,

    In the IQ patch case the AGC is adjusting continuously, I believe after a couple of bit duration ( depending on the symbol rate setting symbolRate.rateWord).

    Which means it will change the gain depending on the input signal level.

    You can try to lock the AGC by writing 0x0588 to 0x40046084 and see how the IQ samples behave in amplitude.

    thanks,

  • 0 in reply to FI
    Expert 1230 points

    Hello FI,

    Thanks for your quick response! Could you please tell me where can I find this register imformation? What does 0x0588 means to this register?

    If I would like to lock the AGC, what command should l use and where should I set it?

    Thank you so much!

  • 0 in reply to Jianlin Zhou
    TI__Mastermind 21280 points

    Hi,

    i am not sure if i can provide this information in open forum. Will get back to you on that.

    You can use HWREG(0x40046084) = 0x0588;

    In your I/Q project do you will have an override looking like HWREG(0x40046084) = 0xWXYZ; 

    This would be the default for AGC.

    Regards,

  • 0 in reply to FI
    Expert 1230 points

    Hello FI,

    Thank you for your reply. If open forum is not allowed, could you send me the information to my email?

    Meanwhile, could you please take a look at my second question about the I/Q sample rate?

    THANKS

  • 0 in reply to FI
    Expert 1230 points

    Hello FI,

    Another question associated with the AGC gain: Is there other ways to read register 0x40046080 value besides reading from memory browser? Is there an api function which I could use?

    Thank you so much!

  • 0 in reply to Jianlin Zhou
    TI__Genius 12740 points

    Hi There,

    I am just following up on some older threads. I have not seen any activity here in a few weeks. I will go ahead and close this for now. If you are still having an issue, feel free to re-open or if the thread is locked create a new thread and reference this one.

    Thanks,

    Riz

  • 0 in reply to Rizwan Murji
    Expert 1230 points

    Helllo Riz,

    Thanks for getting back to me. I definitely would like to know more about this register 0x40046084 which according to previous reply should be used to control AGC gain. I found a similar question which switches to max AGC gain.

    https://e2echina.ti.com/question_answer/wireless_connectivity/hw_rf_proprietary/f/45/p/151141/429457

    I could not find any overriding on this register in my I/Q patch example. According to FI;s reply this register should be like HWREG(0x40046084) = 0xWXYZ. But in the above example dynamic gain should be different. Could you please tell me if there is a way two lock the gain on a certain number? If the gain was set to be too high, will ADC signal be saturated?

    Thanks,

    Jianlin