• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 53 subscribers
  • Views 813 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

How to read RSSI in CC1111EMK868-915

Luisa Altea
Prodigy 90 points
Other Parts Discussed in Thread: CC1111EMK868-915

Hello,

I need to read the RSSI value from my CC1111EMK868-915 Dongle. I am working with IAR Embedded Workbench. I need to use it in the USB testproject to transfer it via USB. For this I am using the ide/usb_app_ex from this page. Further I tried to get the RSSI value following this guide, but when I compile it I get the error that the function

halSpiReadStatus(CCxxx0_RSSI);

in my case CC1111_RSSI (but that does not matter at this point) can not be found. If I search for it in IAR Embedded Workbench using Ctrl+Shift+F to look in ALL files I can not find it either. So I need to get this function anyhow or get the RSSI value in another way.

I hope the description of my problem is precise enough, if not let me know and I will update my question.

Luisa

  • 0
    TI__Guru* 86731 points

    Hi

    CC1111 is a SoC so you do not need a function to read the registers over SPI. This is only necessary for the transceivers. To read the RSSI register you simply write:

    UINT8 test = RSSI;

    Siri

  • 0 in reply to Siri
    Prodigy 90 points
    Thank you, that worked perfectly. Do you further know, if the offset has to be subtracted from this or is it already subtracted?
    With this code I get around -80 to -100 dbM, but both devices are just right next to each other.

    int16_t rssi_dBm;
    rssi_offset = 77;
    rssi_dec = RSSI;
    if (rssi_dec >= 128)
    {
    rssi_dBm = (int16_t)((int16_t)( rssi_dec - 256) / 2) - rssi_offset;
    }
    else
    {
    rssi_dBm = (rssi_dec / 2) - rssi_offset;
    }
  • 0 in reply to Luisa Altea
    TI__Guru* 86731 points

    Hi

    You still need to do all the calculations described in DN505. The only difference is that you read the RSSI directly from a register on a SoC instead of reading via SPI.

    The design note gives you the offset for different data rates and frequency bands on the CC1110.

    BR

    Siri

  • 0 in reply to Siri
    Prodigy 90 points

    I did follow the instuctions and copied the calculation exactly from DN505. But it still get values like "FF A6" which is in my understanding equivalent to -90. It appears that the code above subtracts the offset twice. If I add the offset once to -90 the RSSI seems much more reasonable. But this is only a guess and I need to know how this is exactly calculated and what I am doing wrong. I read DN505 a couple of times again but could not find any clue to my fault.

    BG Luisa

  • 0 in reply to Luisa Altea
    TI__Guru* 86731 points
    What do you mean by saying that you read 0xFFA6?

    The register is only 8 bits.

    If you get 0xA6, this is -90 interpreted as a 2’s complement number. You then divide by 2 and subtract the offset ((-90)/2) – 77 = -122

    BR
    Siri
  • 0 in reply to Siri
    Prodigy 90 points
    OK, I am a bit confused at the moment.
    I took a look at it again and tried to understand it. During this process I tried to read only the RSSI value and output it just in this form. The values I got appeared to be quite reasonable, about between 0xDF and 0xC5. Interpreted they lay around 40 +-10, which is still a little bit to weak, because they are right next to each other.
    But this would mean, that this code:

    rssi_twoComplement = RSSI;

    would deliver directly the value (in 2-complement) which indicates the interesting value. But this is different from your answer, so I am confused.

    BR Luisa