Advertising 128 bit UUID for custom service

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Tue, 27 Sep 2022 19:41:38 GMT

Sniffer is a setup to trace and log the Bluetooth LE traffic with details of packet data so that we can understand the flow of data between peers.

There are few tutorials like this one that can be useful for you.

The user guide for the nRF sniffer is given here.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Tue, 27 Sep 2022 12:00:28 GMT

Hi Susheel,

What is a sniffer trace and how do I provide you with one?

Adam

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Fri, 23 Sep 2022 08:07:18 GMT

Adam,

I just tested this and I see full name in the nrf connect desktop and the services.

Can you provide me a sniffer trace of your data that is being transmitted by the advertiser, it looks right on my side.

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Fri, 23 Sep 2022 06:14:55 GMT

Sorry Adam,

I missed to follow this up, I will test this today, should not take too long, sorry for delays.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Mon, 19 Sep 2022 04:09:22 GMT

Hi Susheel,

Is there any update on this please? It has been nearly two weeks.

Thanks,

Adam

RE: Advertising 128 bit UUID for custom service

adam_atmo — Sun, 11 Sep 2022 03:28:24 GMT

I am using NCS v2.00

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Fri, 09 Sep 2022 09:14:57 GMT

Which SDK version are you using Adam, Unable to compile your code in SDKv2.0

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Thu, 08 Sep 2022 15:56:47 GMT

I will try to test this tomorrow, I think you have given me all the information needed to replicate your setup.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Thu, 08 Sep 2022 12:07:57 GMT

Sorry Susheel, I am still confused as to why I cannot see the full name...

In addition to the code that I have already attached, this is what I have in my prj.conf:

CONFIG_BT_DEVICE_NAME="abcdefghigklmnop"

This is what I see on the Android nRF Connect app:

Regards,

Adam

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Thu, 08 Sep 2022 07:26:31 GMT

I was only calculating the actual payload and excluding the headers and other overheads.

[quote user="adam_atmo"]I don’t have an issue with this when I am not sending scan response data. [/quote]

i believe that you have a solution with this configuration when you are using scan response data aswell.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Thu, 08 Sep 2022 05:20:38 GMT

Thanks Susheel,

However, it seems that it is the introduction of the SD data that limits the length of the name. I don’t have an issue with this when I am not sending scan response data. Have you included the SD data in your calculation?

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Thu, 08 Sep 2022 04:23:01 GMT

the ad seems to be of total bytes of 2 (flags) + 1 type for flags + 6 (HTS+DIS+BAS) + 1 (type for HTS/DIS/BAS) + 1 (length field) = 11 bytes.

So you have 27-11 = 16 bytes for device name + type and length, which equals 14 bytes of actual device name.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Thu, 08 Sep 2022 02:10:09 GMT

Sure, attached below:

static struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA_BYTES(BT_DATA_UUID16_ALL,
		      BT_UUID_16_ENCODE(BT_UUID_HTS_VAL),
			  BT_UUID_16_ENCODE(BT_UUID_DIS_VAL),
		      BT_UUID_16_ENCODE(BT_UUID_BAS_VAL)),
			  { /* TX power adv data */},
};

/* Scan response data.
 * Includes 128 bit UUID for custom RSSI service.
 */
static const struct bt_data sd[] = 
{
	BT_DATA_BYTES(BT_DATA_UUID128_ALL, RSSI_SERVICE_UUID),
};

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Tue, 06 Sep 2022 16:37:05 GMT

[quote user="adam_atmo"]Could this be because the advertising packet is too long to fit the full device name?[/quote]

It most likely is too long. How did you split the adv data and the scan response data? Can you show us your new declaration for ad and sd?

RE: Advertising 128 bit UUID for custom service

adam_atmo — Tue, 06 Sep 2022 05:55:12 GMT

Thanks.

It works now - I was not sending the sd data originally.

However, now the device name is not printing in full whenever I include sd data. I don't have this issue when I am not sending sd data. Could this be because the advertising packet is too long to fit the full device name?

Thanks,

Adam

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Tue, 06 Sep 2022 05:16:01 GMT

Have you split the data you were advertising into advertising data and scan response data in bt_le_adv_start?

In the below code snippet, all data is under ad which is advertising data. You should split this into two ad and sd

static struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA_BYTES(BT_DATA_UUID16_ALL,
		      BT_UUID_16_ENCODE(BT_UUID_HTS_VAL),
			  BT_UUID_16_ENCODE(BT_UUID_DIS_VAL),
		      BT_UUID_16_ENCODE(BT_UUID_BAS_VAL)),
	BT_DATA_BYTES(BT_DATA_UUID128_ALL, RSSI_SERVICE_UUID),
};

RE: Advertising 128 bit UUID for custom service

adam_atmo — Tue, 06 Sep 2022 05:00:54 GMT

I don't see anything about active scanning?

If it does do active scanning, surely I would be able to see the 128 bit UUID? Currently I cannot see this UUID when the device is advertising and this is required.

Thanks,

Adam

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Tue, 06 Sep 2022 03:57:52 GMT

nRF Connect on mobile on Android by default does active scanning. So it sends the scan request to advertiser by default.

If you go in the app->Settings->Scanner->you see all the settings for the mobile scanner there.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Tue, 06 Sep 2022 02:29:32 GMT

Thanks.

How do I request scan response data on Android nRF Connect?

Adam

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Tue, 06 Sep 2022 01:31:57 GMT

[quote user="adam_atmo"]2. Or would it be a better idea to just include the 128 but UUID in the scan response sd data? If so, I am using the Android nRF Connect app - how do I request scan response data so that I can see the 128 bit UUID.[/quote]

I would suggest you to split this advertising data into advertising data and scan response data.

[quote user="adam_atmo"]4. Also, what is the max size in bits for a legacy advertising packet?[/quote]

We have 31 bytes of payload data that we can put in advertising or scan response data. So together you can put 31 + 31 = 62 bytes.

RE: Advertising 128 bit UUID for custom service

adam_atmo — Mon, 05 Sep 2022 07:53:15 GMT

Hi Susheel,

I have attached the relevant code below. I am now getting the following error: too big advertising data. It works perfectly when I leave out the other SIG defined UUIDs. The error probably occurs because I am already advertising three other SIG defined services.

1. Is there anyway to encode this 128 bit data into a smaller number that can be advertised?

2. Or would it be a better idea to just include the 128 but UUID in the scan response sd data? If so, I am using the Android nRF Connect app - how do I request scan response data so that I can see the 128 bit UUID.

3. Any other suggestions?

4. Also, what is the max size in bits for a legacy advertising packet?

Thanks so much,

Adam

Here is my advertising struct:

static struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA_BYTES(BT_DATA_UUID16_ALL,
		      BT_UUID_16_ENCODE(BT_UUID_HTS_VAL),
			  BT_UUID_16_ENCODE(BT_UUID_DIS_VAL),
		      BT_UUID_16_ENCODE(BT_UUID_BAS_VAL)),
	BT_DATA_BYTES(BT_DATA_UUID128_ALL, RSSI_SERVICE_UUID),
};

In my service.h file, I have the following:

#define RSSI_SERVICE_UUID 0xb4, 0xa0, 0x76, 0x45, 0xE9, 0x47, 0xC5, \
                                0x93, 0x9D, 0x9D, 0x03, 0x45, 0x76, 0xA0, 0xB4, 0x49

In my service.c file, I have the following:

#define BT_UUID_RSSI_SERVICE            BT_UUID_DECLARE_128(RSSI_SERVICE_UUID)

RE: Advertising 128 bit UUID for custom service

Susheel Nuguru — Mon, 05 Sep 2022 04:18:57 GMT

Probably some code snippets that you used might help us see the issue. What kind of errors are you getting?

The eddystone sample uses below initialization to advertise all of 128 bit UUID, just an example to show you.

static const struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	/* Eddystone Service UUID a3c87500-8ed3-4bdf-8a39-a01bebede295 */
	BT_DATA_BYTES(BT_DATA_UUID128_ALL,
		      0x95, 0xe2, 0xed, 0xeb, 0x1b, 0xa0, 0x39, 0x8a,
		      0xdf, 0x4b, 0xd3, 0x8e, 0x00, 0x75, 0xc8, 0xa3),
};