Recent Posts

61

Bluetooth Framework / BLE packet loss on receiving notifications

« Last post by mohammad_hosein1 on March 15, 2022, 02:44:09 PM »

Hello dear mike,
I am evaluating the WCl Bluetooth Framework (.NET version). I have an ECG device which is from the company that I work in and it sends ECG signals as notifications using GATT custom service and the length of each packet is 208 bytes.

I was able to use the WPF gattClient app which came with the library itself to print the data on a console window. There is a random amount of packet loss (ranging from zero to 40 packets per minute) on my own laptop which is an ASUS ROG Zephyrus M16. The same behavior was observed on the desktop application I wrote using UWP Bluetooth APIs. I am aware that it is not possible to change the connection interval on windows 10 but other than that is there any way to receive notifications in a more stable setup? Do you have any advice on reducing or eliminating the packet loss?

Also it is important for us to receive the data as fast as possible so we can show the signals in real-time on the display.

Thanks in advance.

62

FAQ / How to Control Bluetooth LE Connection Parameters

« Last post by Mike Petrichenko on February 20, 2022, 07:13:16 PM »

Starting from version 7.14.0 Bluetooth Framework allows to control Bluetooth LE connection parameters. You can find more information about these parameters on our site by this link: https://www.btframework.com/connparams.htm

63

Bluetooth Framework / Re: Connecting GATT Client After Pairing

« Last post by Mike Petrichenko on February 10, 2022, 09:55:58 PM »

You are very welcome. Great that you got it working.

64

Bluetooth Framework / Re: Connecting GATT Client After Pairing

« Last post by briandunham on February 10, 2022, 09:50:47 PM »

Thank you, pairing after connecting is the solution. But that was hidden by an additional problem of the device changing it's MAC I believe.

So for this current stage of development, I'm using a smartphone app to test with while the development on our hardware device catches up. I'm using a Galaxy S9 smartphone with the nRF Connect app. The app allows for building advertisements and has a configurable GATT server. However, the app uses random addresses and it likes to change it's MAC after certain events. I think this is causing issues in addition to your solution of pairing after connecting.

But I'm now aware of the problem and I can figure out a workaround. Thanks!

65

Bluetooth Framework / Re: Connecting GATT Client After Pairing

« Last post by Mike Petrichenko on February 10, 2022, 12:36:14 AM »

Sorry, I forgot to ask, if possible, send more details about your device and how you pair/connect with it to support@btframework.com so we can check it on our side and provide more detailed answer (or fix the problem if it is a bug).

Thank you.

66

Bluetooth Framework / Re: Connecting GATT Client After Pairing

« Last post by Mike Petrichenko on February 10, 2022, 12:28:11 AM »

Hi,

It is known issue(s). Theer are 2 reasons:

1. If your device is mixed (supports both Classic and LE) pairing may be executed with it as with Classic instead of LE.
2. Device changes MAC after pairing.

Any ways. The solution is to pair after connecting: https://github.com/btframework/GattAuth

And of course if yuor device does not require pairing it is better to do not pair with it.

67

Bluetooth Framework / Connecting GATT Client After Pairing

« Last post by briandunham on February 09, 2022, 11:33:42 PM »

Hi,

I've been referencing the GattClient Demo project. I first pair the device successfully then I try connecting the GATT client, but I get error code 0x005105C (WCL_E_BLUETOOTH_LE_DEVICE_NOT_FOUND). However, if I skip the pairing step and just directly connect the GATT client, that it works fine. Is there something about pairing before connecting the GATT client that breaks it? Is pairing first necessary?

68

Bluetooth Framework / Re: Writing to Custom Service

« Last post by Mike Petrichenko on February 07, 2022, 07:57:28 PM »

No problem with UUID. In fact in GATT there is also something known as Short UUID (which is 2 bytes long).

About services reading. Well. In fact there is no something like "services reading" or "characteristics reading". There is just a commands called "read by groups" and "read by type". Both requires handles range. To know characteristic handles range it is required to know service handle. Both commands are mandatory and must be implemented in the device.

69

Bluetooth Framework / Re: Writing to Custom Service

« Last post by briandunham on February 07, 2022, 07:49:18 PM »

I miscounted the number of bytes in the GUID struct. Clearly it's too early in the morning here and I'm not thinking straight. There needs to be a facepalm emoji in this forum.

We're in the beginning stages of adding BLE to our hardware. And also updating the Windows engineering tools to connect to the hardware using your libraries. But you're saying that we need to add support for reading the service definitions from the device? Or else the writing to the characteristics won't work?

70

Bluetooth Framework / Re: Writing to Custom Service

« Last post by Mike Petrichenko on February 07, 2022, 07:37:13 PM »

Not sure what you mean by "hardware currently doesn't support reading any services profiles" but fi the device does not allow to read its services it will never work with any GATT client. It is mandatory feature of GATT specification.

UUID (GUID) is 16 bytes always (by definition, it is 128 bits / 8 = 16 bytes). There is no 20 bytes UUID (GUID) definition (https://en.wikipedia.org/wiki/Universally_unique_identifier)