Ble devices are getting disconnected within 3-4 sec after connection.

[Pritam Lanjewar]

Hi,

We are facing some issues between our ble devices (ble version 5) and android mobiles using nrfsdk ("Android-BLE-Library") library. (Version 2.2)

We are able to connect our devices with mobile phones like samsung, redmi note 8 pro, redmi not 5 pro and other mobiles.

But when we are trying to connect same devices with mobiles like redmi note 8, redmi note 9 pro max and oppo A53. it is getting disconnected within 3-4 sec with gatt timeout error 8.

After tracing bluetooth snoop log we can see below error.
Attribute not found
{
13274 12783.807351 controller host HCI_EVT 8 Rcvd Number of Completed Packets
13275 12783.808066 remote () XiaomiCo_de:0a:37 (Redmi note 9 pro max) L2CAP 497 Rcvd Connection oriented channel
13276 12783.837010 Microchi_95:fc:5a (Endocare) XiaomiCo_de:0a:37 (Redmi note 9 pro max) ATT 74 Rcvd Read By Type Response, Attribute List Length: 3, Unknown, Unknown, Unknown
13277 12783.839225 XiaomiCo_de:0a:37 (Redmi note 9 pro max) Microchi_95:fc:5a (Endocare) ATT 16 Sent Read By Type Request, GATT Characteristic Declaration, Handles: 0x0057..0x0058
13278 12783.842390 controller host HCI_EVT 8 Rcvd Number of Completed Packets
13279 12783.858398 Microchi_95:fc:5a (Endocare) XiaomiCo_de:0a:37 (Redmi note 9 pro max) ATT 14 Rcvd Error Response - Attribute Not Found, Handle: 0x0057 (Unknown: Unknown)
}

We have already tried changing connection parameters like interval, latency and timeout but no luck.

We have attached screen shot of apk log file and hci snoop log file.

Apk Log File :-

Bluetooth HCI Snoop Log :-

[Pritam Lanjewar]

We have tested the devices after increasing the max interval as suggested. Now the connection parameters of the peripheral are, min connection interval is 7.5 ms, max connection interval is 100 ms, latency is 0, and timeout is 5000 ms.
At first we tried normal connection, and were not able to connect. Then, we tried pairing our devices first and then tried connecting again, and were able to connect. Out of the 20 devices we tried we were able to connect to 19 of them after pairing. 1 device still disconnects after about 3 seconds after connection with an unknown error 14.

Is there any way to connect these devices without pairing them first? And any insight on why the devices connects only when paired will be helpful as well.

[Vidar Berg]

Hello,

Excessive clock drift on on the LF 32 KHz source is something that can potentially lead to HCI timeouts. Which clock source are you currently using in your design?   

Best regards,

Vidar

[Pritam Lanjewar]

We are using the Microchip's RN4870/71 BLE module series for now as the peripheral. So the clock source used is the internal 16 Mhz clock source.

[Vidar Berg]

Ok, I suggest that you reach out to Microchip's support then. I am not familiar with this particular module,  and this forum is really for Nordic products.