Discovering a VS UUID Characterisic, but it shows UUID as 0

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hannu Hirvonen — Wed, 17 Apr 2019 07:43:25 GMT

Hello,

I understood so, that you found some mistakes from example project at general and solved it. I followed instructions and played little bit scanning, advertising and so on and after a while scanning didn't work at all. So if example projects doesn't work smoothly then (my opinion) these have to correct. I have seen earlier that when scanning, connecting etc. and try to scan again it doesn't work as expected and I have lost lot of time for investigating how to correct it.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Tue, 16 Apr 2019 13:22:34 GMT

These projects are just example projects, and therefore you should study how these projects work even before going to these forums. Many of these problem are specific to the devices used in that project.

If you were to read the responses to this post, I even uploaded the specific code which solves this problem for my code.

Also if you want more specific answers, you need to write a lot more information about your problem. I suggest you create a new post with the specific problem you have encountered.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hannu Hirvonen — Tue, 16 Apr 2019 08:59:15 GMT

Hello,

So I have to first study how this example project should work or works. Then have to come back and try to do same modifications that you have already done. It would be nice if somebody commits these changes to Nordics official example path and then deliver changes in next release version. Otherwise many of us waste time for investigating already solved problem.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Fri, 12 Apr 2019 07:25:15 GMT

Hi Hannu. My complete solution contains all different kinds of modifications, and some classified information, but I have described above, what is needed. If you read all the replies in this post, you should know what to do.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hannu Hirvonen — Thu, 11 Apr 2019 11:12:55 GMT

Hello Dresse and Hung,

I'm fighting also with same kind of issue. Is this possible to somehow get this correction, so that I don't need to do same things again which has already done (by Dresse).

-Hannu-

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Wed, 28 Nov 2018 09:58:14 GMT

Hey Hung,

If I have some objections/corrections for the example project ble_app_interactive, how should I let you guys know? After working with it for a while, I have stumbled upon somethings, which I believe are errors in the code.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Fri, 23 Nov 2018 11:26:29 GMT

And now it works like a charm! Thanks Hung!

devzone.nordicsemi.com/.../20181123_5F00_121839putty.log

Just a recap for anyone else stumbling upon this problem:
If a custom characteristic, inside a custom service, has a different base UUID, then it needs to be read specifically with sd_ble_gattc_read, this is done as described in the posts above. Since you read on a characteristic declaration it has more than 16 bytes, as Hung described. That just needs to be decoded correctly and you are good to go!

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Fri, 23 Nov 2018 10:09:29 GMT

Hi Dresse,

I think I know what that 19 bytes for. If you have a look here

It's the format of the 0x2803 attribute that you read at handle 62, it's the characteristic declaration, which include: characteristic properties (0x1A), characteristic value handle (0x003F) and the 128 bit UUID.

Base on this you can extract the 128 bit UUID and extract the properties, value handle.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Fri, 23 Nov 2018 09:34:26 GMT

I don't think you need any extra Jlink to test with ble_app_uart. If you have a nRF52 board and a programmer you should be able to do flash and test. We will try to test the sd_ble_gattc_read() function here as well.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Thu, 22 Nov 2018 19:14:21 GMT

Hi Hung,

I thought to let you know, that right now, i'm testing with my phone as a peripheral, where I am using nrf connect app, and then I have entered my custom service UUID and custom characteristic. I'm not going to work until monday, to get the hearingaid. I haven't been able to use the correct hearingaid, since I made the custom code to characteristic, but I'm simulating it with my phone. But I don't think that should be a problem?

Now moving on to the test, I tested it by creating a new command for the CLI, where when I called the command, it would go straight to a sd_ble_gattc_read() with the exact handle i.e. 62, and this gave me the same response with 19 bytes.

I tried to build a new project with ble_app_uart, but that use an extra J-link right? I don't have that, but I don't know if it is easy to direct it to the normal uart connection, so that I can see it via PuTTy?

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Thu, 22 Nov 2018 15:30:44 GMT

Hi,

It's pretty strange to see 19 bytes. I can see the UUID is actually inside that 19 bytes , started from 0x87 ended with 0x6E . It's your first characteristic's UUID.

Could you try to open a new application and try just to do a sd_ble_gattc_read() on that exact handle of the characteristic and see what response you have 16 or 19 bytes ? Then test with a known example (ble_app_uart) so we can reproduce here.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Thu, 22 Nov 2018 14:24:39 GMT

I have been trying to implement it myself, but I am kind of stuck. Inside on_characteristics_discovery_rsp, I have made a check each characteristic that has uuid.type == BLE_UUID_TYPE_UNKNOWN:

        // Save characteristics data.
       for (uint8_t i = offset; i < bytes_to_copy; i++)
       {
           m_srv_char.char_data[i].decl_handle      = p_char_disc_rsp_evt->chars[i].handle_decl;
           m_srv_char.char_data[i].value_handle     = p_char_disc_rsp_evt->chars[i].handle_value;
           m_srv_char.char_data[i].uuid             = p_char_disc_rsp_evt->chars[i].uuid;
           m_srv_char.char_data[i].notify           = p_char_disc_rsp_evt->chars[i].char_props.notify;
           m_srv_char.char_data[i].cccd_desc_handle = 0;

       }

       // If service UUID type is unknown, then try to search for the 128-bit UUID.
       for (uint8_t i = offset; i < bytes_to_copy; i++)
       {
    	   if (m_srv_char.char_data[i].uuid.type == BLE_UUID_TYPE_UNKNOWN){
    		   NRF_LOG_INFO("Characteristic is unknown");
    		   m_vendor_uuid_read_char = true;
			   // Look for characteristic 128-bit UUID.
			   err_code = sd_ble_gattc_read(conn_handle, m_srv_char.char_data[i].decl_handle, 0);
			   APP_ERROR_CHECK(err_code);
			   return;
			 }

           // If characteritics is last.
           if (i == (count - 1))
           {
               m_vendor_uuid_read_char = false;
               // Print services UUID. When you first discover services, the 128-bit UUIDs may not be displayed.
               // In such case, you should rediscover the services.
               uuid_print(p_ble_gattc_evt->conn_handle, mp_device_srv[conn_handle]->services);
           }
           offset++;
       }

After it gets all characteristics, and the types, it check whether one of them is VS UUID, then it calls err_code = sd_ble_gattc_read(conn_handle, m_srv_char.char_data[i].decl_handle, 0);, with decl_handle for the characteristic which type is unknown. I also made a new bool m_vendor_uuid_read_char, so that when i enter on_read_rsp, I know what I asked for. Inside on_read_rsp, I kinda made the same af with service discovery:

    else if(m_vendor_uuid_read_char){
        // Save characteristics uuid data.
       for (uint8_t i = 0; i < m_srv_char.count; i++)
       {
    	   NRF_LOG_INFO("Handle search: %d And reached handle: %d", m_srv_char.char_data[i].decl_handle, p_read_rsp->handle)
    	   if(p_read_rsp->handle == m_srv_char.char_data[i].decl_handle){
    		   NRF_LOG_RAW_INFO("Data len: %d Read data:\r\n", p_read_rsp->len);
			  for (uint8_t i = 0; i < p_read_rsp->len; i++)
			  {
				  NRF_LOG_RAW_INFO("0x%X ", p_read_rsp->data[i]);
			  }
			  NRF_LOG_RAW_INFO("\r\n");
    		  memcpy(uuid.uuid128, p_read_rsp->data, sizeof(uuid.uuid128));
    		  err_code = sd_ble_uuid_vs_add(&uuid, &m_srv_char.char_data[i].uuid.type);
    		  APP_ERROR_CHECK(err_code);
    		  m_srv_char.char_data[i].uuid.uuid = (uuid.uuid128[13]<<8)+uuid.uuid128[12];
    		  NRF_LOG_INFO("m_srv_char.char_data.uuid: %X", m_srv_char.char_data[i].uuid.uuid);
    		  break;
    	   }
       }


       for (uint8_t i = 0; i < m_srv_char.count; i++)
       {
    	   if (m_srv_char.char_data[i].uuid.type == BLE_UUID_TYPE_UNKNOWN)
			  {
    		   m_vendor_uuid_read_char = true;
				  // Look for service 128-bit UUID.
				  err_code = sd_ble_gattc_read(conn_handle, m_srv_char.char_data[i].decl_handle , 0);
				  APP_ERROR_CHECK(err_code);
				  return;
			  }

    	   if(i == (m_srv_char.count -1)){
    		   NRF_LOG_INFO("Characteristics count: %d", m_srv_char.count);
    		   // Print services UUID. When you first discover services, the 128-bit UUIDs may not be displayed.
    		   // In such case, you should rediscover the services.
    		   m_vendor_uuid_read_char = false;
    		   uuid_char_print(m_srv_char);
    	   }
       }
       return;
    }

But now im facing some problems, my data length in p_read_rsp->len, is 19 when receiving the response. I think it might have to do that, i'm asking for the handle of the characteristic declaration, and I it might send more data, than just the char uuid. I'm basically doing the same as in when doing custom Service Discovery. And I have also uploaded my log file for a full overview.

devzone.nordicsemi.com/.../20181122_5F00_152218putty.log

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Wed, 21 Nov 2018 13:55:19 GMT

Thanks, that explains a lot! I will try to implement it myself.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Wed, 21 Nov 2018 10:02:13 GMT

Hi Dresse,

Yes you can test with the ble_app_uart. The GAP role is a little bit different but the service discovery from the GATT client is the same.
We have the base UUID which is the 128 bit UUID and the short 16 bit UUID which is byte 12 and 13 inside the 128 bit UUID. This is explained in the description of sd_ble_uuid_vs_add()

You can use nRF Connect on the phone and do service discovery for the ble_app_uart you can see how the service and characteristic share the same base UUID and only byte 12 and 13 are different.

In your att table, I can see that all characteristics and service have different base UUID.

In this case you would need to modify the ble_m.c library to support UUID read on the characteristic discovery, the same way as we have in the service discovery. Please have a look at on_primary_srv_discovery_rsp() and on_read_rsp() function, where we do a sd_ble_gattc_read() on each service that has the uuid.type == BLE_UUID_TYPE_UNKNOWN

You would need to add the code to do the same when doing characteristic discovery.

I'm a little bit busy at the moment, if I managed to have time I can try to implement but I would suggest you to try first.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Tue, 20 Nov 2018 21:03:22 GMT

So, I don't quite understand what you mean about base uuid. I have attached one of the custom uuid, that is in the hearing aid.

I still have my problem of not being able to see the custom characteristics inside the custom service, well I can see it, but I can't see the specific uuid for it. But if I understand what you said correctly, because my custom characteristics, does not have the same base uuid as the service, it can't see it?

And you are suggesting me to test with ble_app_uart, but do you mean ble_app_uart_c? Because my nrf52 dk is acting as a central and connecting with a peripheral.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Tue, 20 Nov 2018 13:56:39 GMT

Hi Dresse,

I found that in the code, when we find an 128 bit UUID we only assign the value of the 128 bit UUID base into the UUID database, without assigning the 16 bit short UUID of that service to the service uuid. So that why they were all 0. So if you add this line of code

mp_device_srv[conn_handle]->services[i].uuid.uuid = (uuid.uuid128[13]<<8)+uuid.uuid128[12];

after

err_code = sd_ble_uuid_vs_add(&uuid, &mp_device_srv[conn_handle]->services[i].uuid.type);
APP_ERROR_CHECK(err_code);

inside on_read_rsp() in ble_m.c , then you should be able to see the UUID on the first time when you do service discovery.

In addition , in characteristic discovery we won't take in to account that the characteristic may have different base UUID, we assume that the characteristic would have same base uuid as the service.

Could you update the code, and also let me know what the problem you currently have ? I would suggest you to test with the ble_app_uart first before you test with your device.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Tue, 20 Nov 2018 12:54:39 GMT

Thanks Dresse, I have reproduced the issue here with the ble_app_uart. Seems like we have an issue if it's not the 16 bit Bluetooth UUID. I will investigate a little bit more and get back to you.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Tue, 20 Nov 2018 12:53:55 GMT

And another thing, if I connect to the hearingaid using my phone, and using nrf connect, I get all services and characteristics, so the hearingaids works just fine.

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Dresse — Tue, 20 Nov 2018 10:41:08 GMT

Alright, I now have the full log. I have added some extra text to the program, so I know where it is, hope you can see past that. The first log file, show the communation between the hearingaid, and the Nordic.

devzone.nordicsemi.com/.../20181120_5F00_111630putty.log

I also did a test where I try to connect, to my phone, and setting up my GATT server on my phone with a custom service UUID, and custom characteristic UUID. And that worked perfectly:

devzone.nordicsemi.com/.../20181120_5F00_112145putty.log

I think it has to do with some settings in the config file or where ever. The hearing aid have 5 custom VS UUID services and quite a few VS UUID characteristics. I have already turned up NRF_SDH_BLE_VS_UUID_COUNT, but perhaps I have to turn another setting up?

RE: Discovering a VS UUID Characterisic, but it shows UUID as 0

Hung Bui — Mon, 19 Nov 2018 13:05:31 GMT

Hi Dresse,

Please post a full log of your test, including the commands you type in. I don't see the part where you find the VS services I would suggest you also test first with connecting to ble_app_uart, just to test if it would work with a simple custom profile.