bluetooth sample central_uart, how to assign UUID value of scan filter at run time?

[Felix Shih]

Hi,

ncs v2.2.0, sample central_uart. 

It define NUS UUID as scan filter to connect peripheral_uart.

If I want to change the UUID value for scan filter to another value (not nus UUID) at run time,

can you  guide me how to do it?

	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, BT_UUID_NUS_SERVICE);

[Hieu]

Hi Felix, 

To change UUID filter, you can simply call bt_scan_filter_remove_all(), and then add all the necessary scan filters back.

To avoid unwanted callback during the short time the filters are not setup correctly after the remove_all function, it is a good idea to temporarily stop the scan before the remove_all call, then start it again after the filters are setup.

Hieu

[Felix Shih]

Hi Hieu,

I am confused which structure type should I declare at run time to store UUID value and used as bt_scan_filter_add() parameter?

If I declare struct bt_uuid_128 type, it seems not correct.

err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, BT_UUID_NUS_SERVICE);

[Hieu]

Hi Felix,

I got it to work with a setup like this:

#define BT_UUID_NUS_VAL \
	BT_UUID_128_ENCODE(0x6e400001, 0xb5a3, 0xf393, 0xe0a9, 0xe50e24dcca9e)
	
static void setup_filter_1() {
	bt_scan_filter_remove_all();
	static struct bt_uuid_128 nus_uuid = {
		.uuid = {.type = BT_UUID_TYPE_128},
		.val = {BT_UUID_NUS_VAL}
	};
	uint32_t err_code = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, &nus_uuid);
	if (err_code != 0) {
		printk("bt_scan_filter_add %d\n", err_code);
		while(1); // Infinite loop trap for debugging purpose. Do not use in actual production code :)
	}
}

It makes use of the utility macro BT_UUID_128_ENCODE provided by uuid.h. Depends on your use-case, you might want to use the equivalent for 16-bit or 32-bit UUID. Of course, you could also just write your entire UUID as literal byte/char/uint8_t array.