Missing retransmits causing connection drops

TL_SW

The retransmission mechanism is part of the protocol and there is no possibility of it being shut down. Additionally, from the packet capture data you provided, I couldn't find any errors in the SN and NESN sections. The peripheral devices only transmit the next packet after receiving the ACK signal.

Flole

Indeed there is nothing wrong with the SN and NESN, but that's been the case in https://forum.telink-semi.cn/for ... d=1024&pid=3198 aswell. The packet is simply missing as if it was never transmitted in the first place, but the debug logs clearly show that it was queued/scheduled for transmitting. Why could that be?

Flole

I just found another case which shows it more clearly: The central asks for a retransmit as it never received packet 4 but the peripheral does not retransmit but sends an empty PDU instead. It should re-transmit the Error-Response (Attribute not found) until the central acknowledges it. Instead in packet 6 the peripheral sends an empty PDU but with the sequence number 1 again, indicating a retransmit but the data is missing. I am seeing this everytime a packet goes missing, also with the sample code.

TL_SW

Do you mean that if I use the sample code, I can directly see this problem? If that's not the case, please kindly provide entire code.

Flole

Yes, I used the ble_sample without any modifications for testing.

TL_SW

We'll test it with B85m_BLE_Single_Connection_SDK_v3.4.2.4_patch0004. Also, I would like to know about parameters such as connection interval, connection latency, etc

Flole

The interval was 2998.75 milliseconds, latency 0, supervision timeout was 32 seconds.