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CC2500: Loss RX frame

Part Number: CC2500

Hello

I made myself a test monitoring module for thermal chamber tests.

The module makes a bidirectional radio communication with a central station outside the thermal chamber. The chamber varies in temperature between -40 and +80°C with a slope of 1°C/min.

The communication is done with a CC2500 chip and I realized that I was losing messages during the low temperature phases.
I made different tests and in the end I have two modules in the thermal chamber, one that only transmits and the other that only receives. I have a second module that only receives outside, so always at 25°C.
With this last test the module which is outside receives all the frames of the transmitter module but the module of reception which is in the room loses frames when we pass to low temperature

Would you have an idea why I lose frames at low temperature (-10 to -20°C) while the CC2500 is qualified until -40°C ?
Sometimes I receive frames when we are at -40°C but sometimes I have to wait to come back in positive or restart the module electrically to receive frames.

Thanks for your help

  • Hi Gregoire,

    I have a couple of clarifying questions to make sure I'm understanding the issue fully.

    1.  You mention restarting the module allows you to receive frames. Does the system continue to receive frames as long as the temperature does not change again?
    2. At what temperature do you power on the device?
    3. Does your crystal meet all the datasheet requirements over the whole range of operation?

    Regards,

    Jake

  • Hi Jake,

    1. I restarted the module only once and then continued to vary the temperature. The system lost frames again only much later. But during nominal work I can't restart the module
    2. Usually system power ON at 25°C, before temperature variations
    3. Radio Crystal
      • 26MHz
      • freq stability over temperature 10PPM max
      • Operating temperature range -40 to +85°C

    Regards

  • Gregoire,

    Thank you for the additional detail. If I understand correctly the system stops receiving packets completely following a change in temperature but recovers on power cycle and then can stop receiving packets after further temperature variation. The issue would not be with the device itself as it's qualified over the full temperature range. But there could be some implementation details that could effect the packet reception.

    If you are using the wake-on-radio (WOR) feature then please review https://www.ti.com/lit/an/swra126b/swra126b.pdf which describes a case where a RX window could shift if a minimum sleep time is not observed. I could see this being affected by temperature if for some reason calibration of the RC oscillator is incorrect (if it's being disabled in code for some reason). I'm suspicious there may be something here since the system begins to receive again after power cycling. So areas I would check at a first glance would be:

    • verify all calibration settings are correct
    • Verify that T_SLEEP_min is being met in all cases

    Regards,

    Jake

  • Jake,

    Sorry for the delay in answer.

    Wake On Radio is not used in my code and WORCTRL/ WOREVT0 / WOREVT1 are with their default values.

    Did you have another idea ?

    Regards

  • Hi Gregoire,

    One other option to check would be MDMCFG2.DEM_DCFILT_OFF

    When set to MDMCFG2.DEM_DCFILT_OFF=1 the specified device temperature range is from 0C to 85C.

    Jake

  • Hi Jake,

    MDMCFG2 register is set to 0x73 during init radio function and is not called anywhere else.

  • Gregoire,

    Can you verify what frequency you're using and the attempted data rate?

    The errata (https://www.ti.com/lit/er/swrz002e/swrz002e.pdf) points to an issue with spurious signals related to the crystal oscillator. See errata item 8. Can you try a different frequency and let me know if that effects performance.

    Jake

  • Hello Jake,

    Thanks for your help.
    Our radio configuration :

    •  Base frequency : 2433MHz
    • Carrier Frequency : 2474MHz
    • Data Rate : 250kBaud

    We are not exactly on the quatrz armonic, but do you think the problems may be from spirious with quartz temperature drift ?
    Whats would be the best frequency for our application ?

  • Hi Gregoire,

    The choice of frequency here isn't critical. I'd just like to see if the problem remains even after switching to another carrier frequency.

    Some additional questions:

    • What is meant by base frequency of 2433MHz?
    • Can you share the radio configuration files for both the receiver and transmitter? It would make it quicker to evaluate any potential configuration issues.

    Thanks,

    Jake

  • Hello Jack,

    Base frequency was choosen by someone else. If we change radio frequency we may have to change antenna adaptation network...
    We will check if we can do another test with different base frequency.

    We have the same RF configuration file for transmitter and receiver. Is it possible to send file on private link ?

    Thanks

  • Hi Gregoire,

    Yes, I will coordinate with you offline from the E2E forum.

    Jake