Detecting Central device sending scan request

[Chris]

Is it possible on the nRF51822 to surface an every from the Soft Device whenever a client attempt a scan (is it SCAN_REQ?)

This is for an iBeacon implementation where I want to know when a client device (mobile phone) has actually done a scan of the iBeacon.

[Pål Håland]

Hi Chris,

The stack does not notify the application if it have received a scan request.

One way of detecting this is to use the radio notification API. devzone.nordicsemi.com/.../a01296.html devzone.nordicsemi.com/.../a01294.html

By starting a timer when you receive the first notification, and timing it until you receive the end notification, you can see if there is an addition of time spent in the advertising.

BR Pål

[David Edwin]

The alternative would be use the Radio peripheral on the nRF51 to implement the advertising and the handling of the scan request. This means you do not have to use the softdevice. This should be fairly simple to implement but unfortunately no source code is available for this.

[Chris]

Hi Pal,

That sounds like an interesting idea... would it be reliable? Has anyone done something like this before...?

[Pål Håland]

I think this would be pretty reliable, the one thing to keep in mind is that you could have up until 3 scan responses as it is advertising on 3 different channels. It takes about 8us for each byte, and it transmit/receive about 6 byte + adv data/ scan response data for each packet, + 150 us between the adv_data and scan request and between scan req and scan response

[FormerMember]

In the latest version of S110, S110 v8.0.0, you can set the application to receive an event upon scan requests, this is stated in the release notes:" The main features of this release are the ability to set the size of the GATT Server Attribute Table when initializing the BLE stack, the possibilityfor the application to be notified when the SoftDevice receives scan requests, and the ability to disable RF channels for advertising."

Setting the firmware to receive scan requests should be done in the ble_opt_t argument in sd_ble_enable(..): ble_opt_t -> ble_gap_opt_t ->ble_gap_opt_scan_req_report_t.

After setting the scan request option, the scan request are notified with the event BLE_GAP_EVT_SCAN_REQ_REPORT.