What are the conditions for sending a scan request?

[sdi_kei]

Hello.

I am developing using nrf52832 (S132 v7.0.1, SDK v16.0.0) as central and Android device (Bluetooth 4.2) as advertise.
Android devices use nRF Connect.

I can set "Advertising data" and "Scan Response data" in nRF Connect and I want to receive both data. Whether or not these are received is determined by the argument "scan_evt_t" structure of "scan_evt_handler". (Example: p_scan_evt-> params.filter_match.p_adv_report-> type.scan_response)

Currently, after receiving "Advertising data", "Scan Response data" can be obtained on rare occasions.
How can I set central so that I can get "Scan Response data" every time after getting "Advertising data"?

Thank you.

[Joakim Jakobsen]

Hi. 

Currently, after receiving "Advertising data", "Scan Response data" can be obtained on rare occasions.

 What do you mean by rare occasions?

How often do you receive the advertising data, and how often do you receive the scan response data?

What are the advertising and scan parameters for your devices?

Br, 
Joakim

[sdi_kei]

Hello.

Regarding the Scan time setting, interval is set to 0x320 (800ms) and window is set to 0x190 (400ms).
When the reception frequency of 4000ms was measured, the reception frequency of Advertise data was 8 times and the reception frequency of Scan Response was 2 times.
The device Advertise cycle is 100ms. Advertise parameters are Flags, 128bit UUID and Manufacturer Data, and Scan parameters are 128bit UUID and Manufacturer Data.

Thank you.

[sdi_kei]

Hello.

I want you to check. This is because if you can receive "Scan Response data" every time you receive "Advertising data", you know that my software should be set up like the FW you used.

Best Regards.

[run_ar]

Hi

Sorry for the late reply, unfortunately I did not have time to test it this week. but this case is first on my list now, so assuming I will be able to test it next week.

Br,

[sdi_kei]

Hello.

Thank you for your investigation.
I am looking forward to the results.

Best Regards.

[run_ar]

Hi,

It took some time to modify the SDK examples to log this and perform the testing. Testing is performed at my home office without a RF chamber. Both scanner and advertiser is a nrf52832 DK.

In this log you see 22 hits (search in notepad++) for:
<info> app: scan match 7E32890DE6DC

<info> app: scan match 7E32890DE6DC

And there is 2100 hits for:

<info> app: scan match 7E32890DE6DC

<info> app: scan req: 01

Meaning the amount of failing active scans using a nRF52832 as active scanner is close to 1%.

Active scanning RTT log.txt

[sdi_kei]

Hello.

Thank you for your investigation.
The amount of failure is very small at 1%.
It was quite different from the results I posted earlier.

If you have time or equipment, I would like you to conduct a survey with a different Bluetooth version (ver 4.2, etc.) or a survey using an Android device.
The purpose is to see if the amount of failures has decreased because both were nrf52832.

You said that you changed the SDK example. Which example did you use?

I hope you'll tell me.

Best Regards.

[run_ar]

Hi,

Unfortunately I have not had time to test with android this week. But it could be that android does not reply to all scan requests for some reason.

The projects I used for my test are "ble_central\ble_app_uart_c"

8585.ble_app_uart_c.zip

And ble_peripheral\ble_app_uart

8407.ble_app_uart.zip

SDK 17.1.0, and I only tested the pca10040\s132\ses projects.

[sdi_kei]

Hello.

Thank you for the project.
Please check your android when you have time.
It is said that android may not reply to the scan request for some reason, but is this unclear?

Best Regards.

[sdi_kei]

Hello.

But it could be that android does not reply to all scan requests for some reason.

Do you know why this is happening?
I'm sorry you don't have time, but I'd be happy if you could tell me.

[run_ar]

Sorry for not replying sooner. Answering this is speculations from my side, as I do not know how the phone is operating. But the phone would have to time multiplex Bluetooth LE, Bluetooth EDR, WiFi and LTE. So it might not prioritize sending scan responses. Another possibility could be that it is saving power by only sending the advertisement packet, or selectively responding to scan requests.