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CC2640R2F: Periodic 300 ms background activity after stopping advertisement?

Part Number: CC2640R2F

Hi,

   I set our program to stop advertising after 20 seconds so we can do some measurements. After advertisement stop, we notice at the oscilloscope that there is a periodic 300 ms background activity. I have checked our code and there is no clock set to timeout every 300 ms. What is this activity that executes every 300 ms? Is this the watchdog?

- kel

  • What is the duration of the activity? Could this be the DC/DC recharge pulse described in app note SWRA478?

    Best wishes
  • Hi JXS,

    The duration is every 300 ms.

    - kel
  • Can you post a scope plot of the width or time the MCU is active during this pulse? Did you check SWRA478?

    Best wishes
  • Hi JXS,

    I will post a scope plot when we do testing again. I have showed to our Hardware Group SWRA478 regarding the recharge pulse during Standby Mode and they are discussing about it.

    - kel
  • Hi JXS,

         Here is the scope capture. It is the probe 1 yellow lines. The signal today is noisy, but you can see activity every 300 ms. 

    Here is the current consumption after advertising has stopped. I assume this is "Standby Mode". As you can see I am getting maximum current consumption of 7 uA, which probably caused by the 300 ms periodic activity/event.

    - kel

  • Hi JXS,

    How often does this DC/DC recharge happen during Standby Mode. Our hardware engineers are also suspecting this 300 ms periodic event during Standby Mode to be DC/DC recharge . We manage to capture a much better signal of this DC/DC recharge . However it is just a shallow pulse, most probably because of the capacitors we have at our power circuitry. We plan to remove the capacitors and then capture again this signal during Standby Mode.

    - kel
  • Hi Kel,

    Refer to this application note on how to measure current: www.ti.com/.../swra478 . Note that the recharge algorithm is adaptive, so the interval may vary.

    Cheers,
    Fredrik
  • Hi Fredrik,

    We do not have the testing equipment mentioned at swra478. But, we have setup our Fluke Digital Multi Meter to measure current. As you can see from the Fluke Measurements I am getting 1.57 uA average current measurement after I stop advertising. I assume this is Standby Current Measurement. We are hoping to get 1.3 uA which is the Standby Current mentioned at the datasheet.

    Could this periodic event that happens after stopping advertisement, a stack activity?

    - kel
  • Hi kel,

    You will not get the datasheet current consumption value unless you use the DC power analyzer that is used in the SWRA478 app note. A DMM can't provide the same result.

    Question: Do you see the same spike if you modify your simple peripheral task init fxn to NOT enable ADV by default? Another test is to comment out everything in main() except the PIN_init and BIOS_start APIs. This should place the MCU immediately in standby as soon as BIOS_start is called.

    Best wishes