4 Replies Latest reply on Sep 30, 2015 8:52 PM by callmekart

    BCM43362 Abnormal Scan Peak Current

    callmekart

      Hi,

       

      I am looking at some abnormal current consumption during wireless scan.

       

      Murata SN8205, SDK V3.1.2, NetX/ThreadX.

       

      The application loop does a wireless scan frequently. Here is the observation -

       

      Scenario 1 -

      while(1)

      {

           wiced_wifi_scan_networks();

           sleep(2000); // 2 seconds

      }

      Max Current(tek00000.png) - 456.2mA

       

      Scenario 2 -

      while(1)

      {

           wiced_wlan_connectivity_deinit();

           wiced_wlan_connectivity_init();

           wiced_wifi_scan_networks();

           sleep(2000); // 2 seconds

      }

      Max Current(tek00001.png) - 305.2mA

       


      Why will the current consumption be lower after restarting the wireless driver?

       

      Regards,

      Karthik

       

      p.s. - current consumption based on voltage drop across a 0.1Ohm current sense resistor.

        • 1. Re: BCM43362 Abnormal Scan Peak Current
          nsankar

          It is possible due to the PHY calibration that happens in this process to measure the "air"

          • 2. Re: BCM43362 Abnormal Scan Peak Current
            callmekart

            Considering we are using battery powered devices which is sensitive to peak current,

             

            Is it advisable to restart the WLAN interface before each scan?

            • 3. Re: BCM43362 Abnormal Scan Peak Current
              nsankar

              For battery powered devices in general you shouldn't be scanning periodically and restarting the WiFi driver periodically is also not a good answer. And if you have peak current limitations - I would suggest you talk to your Murata rep and get support on customizing a solution for this.

               

              You may have to tradeoff RF performance for this.

               

              The reason the PHY needs to re-calibrate periodically is to maintain best RF sensitivity and reference over time as the environment changes due to temperature etc.

               

              Is there a reason you are scanning so often?

              • 4. Re: BCM43362 Abnormal Scan Peak Current
                callmekart

                Our application uses the WiFi scan for other purpose, eg. to establish Ad-Hoc communication.

                 

                The reason for looking at peak consumption is only to extend the rechargeable battery life over a single charge.

                We can compromise RF Performance for longer run time.

                 

                Any suggestion for WiFi software configuration to minimize the peak current?

                The WiFi duty cycle for our application is very small, transmit data at a very low frequency(once per hour).