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Frequent scanning of multiple BLE beacons

Maximilian Wiens

I read this thread: nRF51 beacon high frequency scanning and advertising and have similar problem here.

Some repost from my electronics.stackexchange.com question

I have 3 Atmel MCU based BLE scanners, each uses TI CC2540 based BLE HM-11 module PDF USer Manual chip to scan for the advertise packets (bluetooth Beacons) around. There are approx. 10 Beacons at a time around the scanner sending advertisiment packets every 100ms. The scanner needs only Minor, Major and the txPower of the each beacon.

The scanner sends an "AT+DISI" (start Beacon discovery s. User Manual) command over serial interface to the BLE Module and waits for the data response.

Everything works, but the time, until all data completely arrives takes around 5 seconds. Since I want to scan for the Beacons one or two times a second, I need to improve the scanning time.

Beacon properties:

  • Possibile avertising interval of 20ms - 100ms
  • Optional: custom interval values (so i can set prime numbers for less collision)
  • Optional: sending on constant frequency (2480MHz)
  • Less payload (I need only Major, Minor and txPower / RSSI)

Scanner properties:

  • Possible to scan 1-3 times a second
  • Possible to scan 10-20 beacons at the time
  • Optional: scanning on the constant frequency (2480MHz)

Which chip should be used for the beacons? (maybe nRF51822?)

Which chip should be used for the scanners? (maybe nRF51?)

Is it useful to take nRF51 DK for experiment purposes?

Thanks in advance for the answers.

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  • 0

    I would recommend testing with nRF52 DK, our latest and greatest device.

    With BLE stack, SoftDevice S132 v2, you can:

    • Set an advertising interval between 20 ms to 10.24 ms in 0.625 ms steps. The actual minumum advertising interval will vary between 20 ms and 30 ms because of random delay. This is per spec, there are ways to obtain less.
    • Advertise on a single channel, for example channel 39 (2480 MHz)
    • Have a payload between 0 and 31 bytes.
    • Scan continously (as long as the radio is available), or for a certain amount of time 1-3 times a second

    You cannot:

    • Scan on a single channel, but there are ways of doing that, see this.

    Can't answer "Possible to scan 10-20 beacons at the time", need more information. The best way to know is to test.

Reply
  • 0

    I would recommend testing with nRF52 DK, our latest and greatest device.

    With BLE stack, SoftDevice S132 v2, you can:

    • Set an advertising interval between 20 ms to 10.24 ms in 0.625 ms steps. The actual minumum advertising interval will vary between 20 ms and 30 ms because of random delay. This is per spec, there are ways to obtain less.
    • Advertise on a single channel, for example channel 39 (2480 MHz)
    • Have a payload between 0 and 31 bytes.
    • Scan continously (as long as the radio is available), or for a certain amount of time 1-3 times a second

    You cannot:

    • Scan on a single channel, but there are ways of doing that, see this.

    Can't answer "Possible to scan 10-20 beacons at the time", need more information. The best way to know is to test.

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