Avoid service discovery

RE: Avoid service discovery

Marjeris Romero — Mon, 29 Jul 2019 14:55:43 GMT

Hi Jens,

So if I understood correctly you are expecting a write event which is not being sent? I agree with Runar and think you should check if you are actually sending the write and also if you are writing to the right characteristic.

I am also not completely sure of what you are trying to implement. If you want to avoid service discovery, then the central (GATT client) needs to catch the peripheral's gatt server attribute table, this means you should do service discovery one time (first time) and then store the peripheral's gatt server attribute table (and handles) in you central. It does not make sense to me to hardcode the attribute handlers in the gatt server.... could you just explain a bit more about what you are trying to achieve and how?

Did you read the user guide for the nRF sniffer? You need to install the nRF sniffer extension in Wireshark.

Best regards,
Marjeris

RE: Avoid service discovery

Jenzo — Sun, 28 Jul 2019 13:52:01 GMT

I have installed the sniffer program on the PCA10040 board. LED is toggling. So it should be picking up BLE packets.

But Wireshark is not showing nRF sniffer interface.

What could be wrong?

RE: Avoid service discovery

Jenzo — Sun, 28 Jul 2019 12:01:29 GMT

I am getting connect & disconnect events both in my custom service event handler and the main function.

However in the main ble event handler and the custom service event handler I do NOT get the write event! What could be the reason for not receiving any write events in the ble event handler?

When I connect the ble event handler is called!

RE: Avoid service discovery

Marjeris Romero — Mon, 08 Jul 2019 11:55:42 GMT

Hi,

It seems you have been using the old sniffer, could you try and see if it works better for you with the nRFSniffer v2? User guide here and download link here.

RE: Avoid service discovery

Jenzo — Thu, 27 Jun 2019 12:24:38 GMT

Hi,

handling of the MTU request does not have an effect. Still if I do service discovery, everything works fine. My custom central can control my custom peripheral.

The sniffer is a bit cumbersome. I have used Wireshark, but I need to start a DOS prompt first and find the device and then hope for Wireshark to start up correctly - seldomly happens. Do you have another and better way of sniffing?

RE: Avoid service discovery

run_ar — Tue, 18 Jun 2019 08:57:54 GMT

Hi,

I am sorry for the late reply. Could you post the sniffer trace here?

Also please check to make sure you are handling incomming ATT MTU requests, S130 will probably just reply with unknown procedure, but for S132 you will have to handle this in the application. GATTS ATT_MTU Exchange

RE: Avoid service discovery

Jenzo — Mon, 03 Jun 2019 10:57:49 GMT

I am using SDK 15 - I am using S132. Chipset nRF52832. I am using Segger Studio.

Write is actually sent on air!

I do service discovery in nRFConnect - all works fine!

Still when I use my custom board - as central - without making service discovery, then it does not work! I am not getting any ble events - also no ble events in main.

RE: Avoid service discovery

run_ar — Thu, 23 May 2019 14:21:26 GMT

Unfortunately I am not familiar with that example, but seems like it is written for nRF5 SDK v15, while you are using sdk13? Would it be possible to use the latest Softdevice and SDK version?

Anyway, Can you check with a sniffer that the write is actually sent on air?

Did you do a service discovery in nRFConnect?

Also, could you check in the main ble event handler if you get the write event there?

RE: Avoid service discovery

Jenzo — Wed, 22 May 2019 14:16:56 GMT

I am following the GitHub example (custom_ble_service - bjornspockle) line by line, but I do not get a on_write event when I send a byte from nRFConnect?!? I am using SEGGER Studio.

What could be wrong?

RE: Avoid service discovery

run_ar — Tue, 21 May 2019 11:58:39 GMT

No, I do not think there is any particular difference in that sense. The only thing I can think about is there are some actions that happen based on the service discovery, Are you sure you enable the cccd's etc? Have you tried to capture a sniffer trace to see what is happening?

RE: Avoid service discovery

Jenzo — Mon, 20 May 2019 10:52:37 GMT

I have tried on an older peripheral (nRF51 and S110) and that works without service discovery on my central. Any difference between S110 and S132? The code is almost identically.

RE: Avoid service discovery

Jenzo — Mon, 20 May 2019 09:19:40 GMT

It works perfectly when I do service discovery on my central, but as soon as I switch of service discovery I can connect but I do not get on_write event even though the handles are hard coded.

I am not new to service and char, but I read through the tutorials just to be sure.

What could I do wrong?

RE: Avoid service discovery

Jenzo — Thu, 16 May 2019 13:25:26 GMT

On the GATT server I have hard coded the handles:

#define BLE_LOCK_STATUS_HANDLE 0x0014

#define BLE_LOCK_STATUS_CCCD_HANDLE 0x0015

#define BLE_LOCK_CMD_HANDLE 0x0017

#define BLE_LOCK_NAME_HANDLE 0x0019

#define BLE_LOCK_VERSION_HANDLE 0x001B

Still does not work. What do I need to do on the client side to make it work?

RE: Avoid service discovery

run_ar — Thu, 16 May 2019 09:10:36 GMT

The gatt server on the peripheral does not do service discovery. You can connect to you peripheral using nRF connect to check what attribute handle your custom characteristic has, it is not 0x0001.

If you need additional information on how to set up the service and characteristics I would recommend that you take a look at our tutorial section here.

RE: Avoid service discovery

Jenzo — Thu, 16 May 2019 06:39:59 GMT

sorry - uint16_t. But is it correct to hard code it with the value 0x0001. I only have one custom service.

RE: Avoid service discovery

Jenzo — Wed, 15 May 2019 13:32:04 GMT

Hi,

it is the gatt server on the peripheral!

How do you hard code the attribute handle on the gatt client? The handle is a unint8 - do I set it to 0x0001?

RE: Avoid service discovery

run_ar — Wed, 15 May 2019 12:42:05 GMT

Hi,

I am slightly confused, is the gatt server on the peripheral or on the central? Regardless you should probably disable the Database Discovery Module if you do not want to do service discovery. But please note that you will have to hard code the attribute handles on the gatt client if you do not do service discovery.