How can I tell that a Bluetooth channel is busy

RE: How can I tell that a Bluetooth channel is busy

Kenneth — Mon, 11 Jun 2018 09:01:19 GMT

Correct.

RE: How can I tell that a Bluetooth channel is busy

Kenneth — Mon, 11 Jun 2018 09:00:44 GMT

Good idea. That may actually work yes.

Best regards,
Kenneth

RE: How can I tell that a Bluetooth channel is busy

Andre — Fri, 08 Jun 2018 11:33:02 GMT

I wonder, would it be possible to request a timeslot (devzone.nordicsemi.com/.../setting-up-the-timeslot-api) from the softdevice, so that the radio can be accessed from the application, and then perform a channel measurement manually? Set channel, and then repeat a rssi measurement a few times, to calculate an average signal strength on the channel. And then exit the time slot.

// Set up radio for scanning
	// Make sure the radio is powered on
	NRF_RADIO->POWER = 1;
	// Make sure the radio is not doing an RSSI measurement at the moment
	NRF_RADIO->EVENTS_RSSIEND = 0;
	// Flush Cache 
	__DSB();
	// Reception must be enabled in order to measure RSSI
    NRF_RADIO->TASKS_RXEN = 1;  
    NRF_RADIO->TASKS_START = 1;
    while(NRF_RADIO->EVENTS_READY == 0);
    NRF_RADIO->EVENTS_END = 0;
    __DSB();
    
// Scan
    int rssi = 0;
    for (int i = 0 ; i < NR_OF_SAMPLES; i++) {
        // Set radio channel
        NRF_RADIO->FREQUENCY = channel;
        // Start RSSI measurement
        NRF_RADIO->TASKS_RSSISTART = 1;
        __DSB();
        // Wait for measurement to finish
        while (!NRF_RADIO->EVENTS_RSSIEND);
        // Accumulate results 
        // N.B. NRF_RADIO->RSSISAMPLE contains positive values. Eg 20 means -20dB
        rssi += NRF_RADIO->RSSISAMPLE;
    }

Then if the average rssi is too high (N.B. the lower the value, the higher the signal), exclude it. One thing you need to keep in mind is that the bluetooth channels don't map one-to-one to radio channels.

RE: How can I tell that a Bluetooth channel is busy

tvik81 — Fri, 08 Jun 2018 11:02:57 GMT

Hi Kenneth,

Thanks for the answer.

This feature is available in version 6.0 only, isn't it?

Best regards,

Viktor

RE: How can I tell that a Bluetooth channel is busy

Kenneth — Thu, 07 Jun 2018 12:30:41 GMT

Hi,

In the latest v6.0 softdevice there is QoS channel survey feature, please see migration document in the release:
http://www.nordicsemi.com/eng/nordic/Products/nRF52832/S132-SD-v6/67248

I don't see any way to do this in previous softdevices.

Best regards,
Kenneth