2 Replies Latest reply on Oct 17, 2018 4:54 AM by JeBl_3106276

    Wifi chip transmits when monitor mode is enabled

    JeBl_3106276

      I have made an application in WICED SDK that uses the monitor mode functionality. I have noticed that whenever monitor mode is enabled (or if the channel is changed during monitor mode) the chip transmits a "narrow band"  signal with a duration of approximately 30-40 ms. I've boiled things down to the following simple application

       

      void application_start( )

      {

          wiced_init( );

       

          wwd_wifi_set_channel(WICED_STA_INTERFACE, 6);

       

          while (1) {

              wwd_wifi_enable_monitor_mode( );

       

              wiced_rtos_delay_milliseconds(200);

       

              wwd_wifi_disable_monitor_mode( );

          }

      }

       

      Every time wwd_wifi_enable_monitor_mode is called a high powered narrow signal is transmitted. In the test code above channel 6 (2437.0 MHz) is set prior to toggling monitor mode. In this case the narrow band signal appears at 2439.0 MHz as seen in

      Screen_0046.png

       

      Switching to zero span on 2439.0 MHz shows the time aspects of the signal

      Screen_0044.png

       

      Every time monitor mode is enabled (in the test application this i every 200 ms) these transmit signal can be observed. The measurements are done radiated on a CYW943907AEVAL1F board.

       

      How can I avoid this? These high powered CWs should not be there - my application should never transmit anything.

       

      Is it possible to completely disable the TX path of the module?

       

      I'm using:

      board: CYW943907AEVAL1F

      WICED SDK version: 006.002.001.0002

       

      Any pointers on how to avoid this are much appreciated.

       

      /Jesper