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inaccurate RSSI value on the keyfob of CC2541 mini-dk

John Zhang3
Prodigy 20 points
Other Parts Discussed in Thread: CC2541

Hi,

I am trying to read RSSI value on the keyfob of CC2541 mini-dk which is connected by my iOS app. RSSI reading works, but the value returned seems inaccurate (lag behind) to me. Can anyone shed some light on this problem?

Here is the related code:

in void KeyFobApp_Init( uint8 task_id )

uint16 rssi_read_rate = 1000;

GAPRole_SetParameter( GAPROLE_RSSI_READ_RATE, sizeof( uint16 ), &rssi_read_rate );

callback function:

static void peripheralRSSINotificationCB( int8 newRSSI ) {

   // notify iOS app new RSSI

}

Thanks,

John

  • 0
    Prodigy 20 points

    Here are the RSSI values I logged from both key fob side (peripheral) and iPhone side (central). As you can see, peripheral rssi value seldom changes and response slowly to the distance change between key fob and iPhone.

    2014-08-10 22:59:29.879 peripheral rssi: -32
    2014-08-10 22:59:29.882 central rssi: -38
    2014-08-10 22:59:31.379 peripheral rssi: -32
    2014-08-10 22:59:31.382 central rssi: -40
    2014-08-10 22:59:32.879 peripheral rssi: -32
    2014-08-10 22:59:32.882 central rssi: -42
    2014-08-10 22:59:34.379 peripheral rssi: -32
    2014-08-10 22:59:34.382 central rssi: -46
    2014-08-10 22:59:35.879 peripheral rssi: -32
    2014-08-10 22:59:35.882 central rssi: -51
    2014-08-10 22:59:37.379 peripheral rssi: -32
    2014-08-10 22:59:37.382 central rssi: -52
    2014-08-10 22:59:38.879 peripheral rssi: -32
    2014-08-10 22:59:38.882 central rssi: -69
    2014-08-10 22:59:40.379 peripheral rssi: -32
    2014-08-10 22:59:40.382 central rssi: -63
    2014-08-10 22:59:41.879 peripheral rssi: -32
    2014-08-10 22:59:41.883 central rssi: -65
    2014-08-10 22:59:43.379 peripheral rssi: -87
    2014-08-10 22:59:43.384 central rssi: -67
    2014-08-10 22:59:44.879 peripheral rssi: -87
    2014-08-10 22:59:44.883 central rssi: -55
    2014-08-10 22:59:46.379 peripheral rssi: -87
    2014-08-10 22:59:46.383 central rssi: -57
    2014-08-10 22:59:47.881 peripheral rssi: -87
    2014-08-10 22:59:47.884 central rssi: -88
    2014-08-10 22:59:49.379 peripheral rssi: -87
    2014-08-10 22:59:49.382 central rssi: -70
    2014-08-10 22:59:50.879 peripheral rssi: -87
    2014-08-10 22:59:50.883 central rssi: -70
    2014-08-10 22:59:52.379 peripheral rssi: -87
    2014-08-10 22:59:52.383 central rssi: -69
    2014-08-10 22:59:53.880 peripheral rssi: -87
    2014-08-10 22:59:53.883 central rssi: -77
    2014-08-10 22:59:55.383 peripheral rssi: -59
    2014-08-10 22:59:55.387 central rssi: -69
    2014-08-10 22:59:56.880 peripheral rssi: -59
    2014-08-10 22:59:56.884 central rssi: -71
    2014-08-10 22:59:58.380 peripheral rssi: -59
    2014-08-10 22:59:58.384 central rssi: -69
    2014-08-10 22:59:59.878 peripheral rssi: -52
    2014-08-10 22:59:59.880 central rssi: -66
    2014-08-10 23:00:01.379 peripheral rssi: -52
    2014-08-10 23:00:01.382 central rssi: -67
    2014-08-10 23:00:02.879 peripheral rssi: -52
    2014-08-10 23:00:02.882 central rssi: -63
    2014-08-10 23:00:04.379 peripheral rssi: -52
    2014-08-10 23:00:04.382 central rssi: -66
    2014-08-10 23:00:05.879 peripheral rssi: -52
    2014-08-10 23:00:05.882 central rssi: -69
    2014-08-10 23:00:07.379 peripheral rssi: -52
    2014-08-10 23:00:07.382 central rssi: -65

  • 0 in reply to John Zhang3
    Expert 1035 points

    If you repeat this test with WiFi off (disabled on the phone) do you still see this variation?  Some phones do not do a good job with their antenna diversity.  I haven't seen issues with iPhone before, but just in case you have a lemon.