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CC1101 modules.

James Anderson21
Prodigy 30 points

Other Parts Discussed in Thread: CC1101

Hi, not sure if this is the right place to ask this or not.

I have two types of CC1101 modules. One marked D-SUN CC1101 an one marked RF1100SE both 433MHz.

The D-SUN modules can talk together and RF1100SE modules can talk together. However the D-SUN module and the RF1100SE module will only talk together if I set the modulation format of the radio signal to ASK/OOK on the D-SUN module and the modulation format on the RF1100SE to either FSK-2 or GFSK. All other registers on the CC1101 are identical. I realise that I am at the mercy of whoever manufactures the modules but would I be right to expect them to be able to communicate if both are set to 2-FSK, GFSK or ASK/OOK or am I missing something fundament?

  • 0
    TI__Guru**** 317180 points
    The typical cause in cases like this is that the center frequency has a offset on one or both module types.

    If you have access to a spectrum, set the module to send a CW and measure the frequency on both types. You typically have to increase the RX BW on the receiver to take into account the frequency offset between the modules. If you do some calculations the frequency doesn't have to be many ppm off before you will not be able to receive.
  • 0 in reply to TER
    Prodigy 30 points

    Hi, really appreciate the answer. I don't have a access to a spectrum but by trial and error I changed MDMCFG4 from 100KHz to 150 KHz and all has sprung in to action between both types of Module. Can I ask if there is a simple explanation as to why if the two modules had exactly the same value that one received and one did not?

    But once again - many thanks for the answer it has resolved the issue.

  • 0 in reply to James Anderson21
    TI__Guru**** 317180 points
    They are probably using a slightly different xtal. Everything in the CC1101 is derived from the reference which is the xtal frequency. Typically the xtal frequency is a function of the xtal tolerance (+-10/20/30 ppm) and the load cap. The parasitics on the PCB is part of the load and the parasitics is probably different on the two modules you have giving a slightly different center frequency.
  • 0 in reply to TER
    Prodigy 30 points
    Great thanks really appreciate your help.