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CC2530 frequency settings

c_ 64
Intellectual 630 points
Other Parts Discussed in Thread: CC2530, CC2541

Hi,

I'm transmitting an unmodulated carrier from a CC2530 development board to a spectrum analyzer, but the expected output frequency does not correspond with the measured frequency, so I'm wondering if there is some kind of tuning one needs to do. I set the following registers:

MDMCTRL0      = 0x85; 
MDMCTRL1      = 0x14; 

and use FREQCTRL to control the frequency. However, if I use FREQCTRL = 0x00, I get an output frequency of 2394 MHz, and not 2379 MHz, as the data sheet states. Also, 0x74 gives 2507 MHz, so it seems like the frequency range is just shifted a bit. Any ideas what this is?

  • 0
    TI__Mastermind 39860 points

    First test is to try one of the frequencies in the 2.4 GHz band. Lower IEEE 802.15.4 channel is 0x0B, corresponding to 2405 MHz. 

  • 0 in reply to Sverre
    Intellectual 630 points

    The spec sheet states "The carrier frequency is 2379 + n MHz, where n is the value of this register, and n can be from 0 to 116. This gives a frequency range from 2379 MHz to 2495 MHz." So if I'd like a carrier of 2450 MHz, I would use n = 71 (or 0x47), but this gives me a 2465 MHz carrier. Instead, if I use 2394 MHz as the starting point (which is what I get when setting FREQCTRL = 0x00), and aim at getting 2450 MHz as output, I set n = 56 (or 0x38), and voila, I get 2450 MHz as output. Does this mean that my development card is not according to spec? Or am I missing something?

  • 0 in reply to c_ 64
    TI__Mastermind 39860 points

    The carrier frequency is 2394 MHz + n MHz. Using n = 0x38 (=56d) gives a carrier of 2450 MHz. This is according to the description in SmartRF Studio, data sheet, User Guide and also what you get.  

    See User Guide, section 23.5 (I believe you have looked at the CC2541 part of the UG, section 25.5). 

  • 0 in reply to Sverre
    Intellectual 630 points

    Ah yes, silly me! I opened the document from a link and did a CTRL+F for FREQCTRL in the pdf viewer, and didn't think about that it described two different chips. No wonder I got a different output from what I expected. Thank you!