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LAUNCHXL-CC1350: testing cc1350 against electrical noise from dcdc converter

Expert 1190 points

Replies: 4

Views: 93

Part Number: LAUNCHXL-CC1350

Hello,

I'm facing problems in setting up a WSN based on cc1350 launchpads and I don't know where the problem is.

When I test the devices on my desk everything works perfectly, however when I try to deploy them outdoor it looks like they are out of communication range (no packets received at the sink). The nodes are approximately 50m (or less) apart one from each other.

Since I had some problems with the dcdc converter I use (see this question) I though the problem was caused by electrical noise around the board. To verify if this is actually the problem I'm trying to use smartRF studio, the idea is to turn the device in continuous RX and compare the RSSI floor obtained with our power supply board (based on tps62030) with the RSSI obtained when the launchpad is powered with its on board regulator.

Results are very similar: from -100dBm to -108dBm with onboard regulator, from -98dBm to -104dBm with the tps62030 (keep in mind that I'm performing the test in an office environment that is not noise free). Given these results, can I conclude that the noise floor captured by the antenna in the two cases is very similar and hence the problem is given by the electrical noise?

In the next days I'll do some range test using smartRF studio with and without the tps regulator, is there any other test I can do to debug this problem?

Thank you,

Davide.

Davide Giovanelli - FBK Trento (Italy)

  • Expert 8740 points
    Hi,
    From what you report i think noise is playing a role.
    To have more confidence in the measurements, I suggest you do conducted sensitivity tests as well to rule out any possibility interfere in the environment.
  • Guru 240310 points

    In reply to FI:

    Have you tried to follow the datasheet values for the inductor on the DCDC board for these measurements?

     OOO until September 30th. If your thread is not answered by someone after 2-3 days after your last post, please repost with a link referring to your original post. 

  • In reply to TER:

    The measurements have been taken with and without the dcdc with very minor difference in the result, therefore, even if the dcdc is responsible for the bad links, I don't think the RSSI floor measurement is a good estimator for electrical noise injected by the power supply.

    However the inductor is quite big (47uH) with respect to the suggested value (1.5uH) and I don't have this value in the lab, I just found a 3.3uH.

    Since I expect the effect of the noise not to be on/off, I wanted a way for measuring it. Otherwise I could simply change the inductor, test it on the desk (where it will work) but then I don't have any guarantee that the radio is not affected at all.

    Therefore today I'll perform some range test with all the variants I have (without the dcdc, dcdc with 47uH and dcdc with 3.3uH, power save enabled and power save disabled) then I'll report here the results.

    Davide Giovanelli - FBK Trento (Italy)

  • In reply to Davide Giovanelli:

    While I'm waiting for the proper inductors to arrive, I did some ranging test. I didn't found a relevant difference in the communication range when using the dcdc or the on board regulator of the launchpad. Therefore, till the dcdc is not in power save mode everything works as expected.

    I can close this question since it was related only to the noise measurement that apparently cannot carried on using only the cc device+smart rf studio.

    Davide Giovanelli - FBK Trento (Italy)

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