Scan filtering with address

RE: Scan filtering with address

mhakbilen — Tue, 05 Sep 2023 08:21:14 GMT

Thanks.

RE: Scan filtering with address

mahq — Tue, 05 Sep 2023 05:16:23 GMT

Hello, as written in this topic above I did scrap my idea of connecting to peripheral devices using the mac address. I went for using the short name filter instead.

Kind regards,

RE: Scan filtering with address

mhakbilen — Fri, 25 Aug 2023 06:06:02 GMT

[quote userid="121988" url="~/f/nordic-q-a/95065/scan-filtering-with-address"]The adress sticks the same after reboot.[/quote]

Hi mahq,

I am having trouble connecting to the MAC address. I would like to talk to you about this problem. Can you share your e-mail address or LinkedIn address?

Best regards,

RE: Scan filtering with address

mahq — Tue, 10 Jan 2023 11:32:09 GMT

Hello,

Did some more investigations on my own and found out that, if you are using a name filter when scanning (using SDK 2.0.2) it will be up to the peripheral to decide on how many characthers to match in the filter.

I.e. if the central device has a filter named "Filter01" and a perihperal device is advertising with the name "F" this will be considered as a filter match.

I will instead use the ShortName filter since then the central device will control that the advertising name is fulfilling the "min_len" specified in the data type "bt_scan_short_name".

kind regards,

RE: Scan filtering with address

Susheel Nuguru — Tue, 10 Jan 2023 08:42:14 GMT

Hi, I have been sick for few days and did not get time to test this. I do not know that format of the scan filter over the top of my head but I will try to test your code snippet this week when I am back to office. Sorry for the delays so far and thanks a lot of your patience.

RE: Scan filtering with address

mahq — Mon, 02 Jan 2023 06:44:23 GMT

Thank you for you answer. Didn't really get your proposal to work.

However I'm trying another apporach where the "connect_if_match" always is set to true and instead applying different name filters instead of an address filter.

In order to separate between different units (peripherals) i want to use a similar name string for my units in the advertise data and scan filter which will have the format of some characters and two digits ex. "Filter01", "Filter02", "Filter03" etc. etc.

I have a function in my central unit according to the code below in order to change between different filters and in that way connect to different peripherals:

void update_filter(char filter_number[3]){
	int err;
	char connect_string[] = {'F', 'i', 'l', 't', 'e', 'r', filter_number[0], filter_number[1], 0 };
	
	printk("changing filter to %s \r\n", connect_string);
	bt_scan_filter_remove_all();
	bt_scan_filter_disable();
	
	
	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_NAME, connect_string);
	if (err) {
		printk("error adding filter %d \r\n", err);
		LOG_ERR("Scanning filters cannot be set (err %d)", err);
		return err;
	}

	err = bt_scan_filter_enable(BT_SCAN_NAME_FILTER, true);
	if (err) {
		printk("error enabling filter \r\n");
		LOG_ERR("Filters cannot be turned on (err %d)", err);
		return err;
	}

}

Though when applying the filter it doesn't seem that a complete string match is needed in order to trigger a filter match. When applying a filter according to the code above (the scan_init functions has already been initialized) my central unit can connect to any random bluetooth unit in my office.

I do not get any error message so I assume that the filter is properly added and enabled.

Do I need to format my name filter in any certain way or doesn't a name filter require a complete match of the filter string in order to trigger a filter match?

Kind regards,

RE: Scan filtering with address

Susheel Nuguru — Wed, 28 Dec 2022 08:39:39 GMT

You would have to reinitialize the scanner module with connect_if_match set.

Other was is to directly edit the structure defined in NRF_BLE_SCAN_DEF(X) to change its X->connect_if_match = true when you need it.

RE: Scan filtering with address

mahq — Tue, 27 Dec 2022 13:37:50 GMT

Found a solution to my issue,

I was calling the incorrect function (bt_addr_to_str instead of bt_addr_le_to_str after connecting to perephiral) hence a deviation between the addresses.

Also must the input type pointer to the bt_scan_filter_add be of type "bt_addr_le_t" when using the filter type "BT_SCAN_FILTER_TYPE_ADDR".

I do, however, have another question;

I would like the central unit to first scan for a generic name filter in order to list all mac-addresses (of the peripherals) which matches this filter but I don't want an automatic connection. Then I would like the central unit to apply one filter with a specific mac-address in order to connect to only one of the matching units.

I'm trying this procedure and I do manage to get a filter match with only one mac address after first listing all devices matching the generic name filter. But the central unit is not connecting to the chosen peripheral.

For the first scanning i'm calling the scan_init function where I set the ".connect_if_match" to false, when changing the filter to an address-filter I'm first calling the scan_init function a second time and setting the ".connect_if_match" to true. Is this possible scenario or is it only possible to set the "bt_scan_init_param" one time?

Kind regards,