NRF52 cannot connect to BLE 4.1 phone (Nexus 6 with Android 7.1.1)

[aircheese]

Hi,

We are developing a wireless sensor for research purpose using NRF52. I was always develop under Bluetooth 5.0 environments. The phone i am always using is Xiaomi MI 6, which supports Bluetooth 5. We are using data length extension for higher data rate. 

Recently, we want to support older 4.1 and 4.0 device. I tried a few time but failed.

Hardly i set up the NRF Sniffer with Wireshark. Here are the logs.

This log is from Xiaomi MI 6 (Bluetooth 5). In this log both central and peripherals are working fine.

When i tried with Nexus 6 (Bluetooth 4.1). The connection cannot be established. Peripheral disconnects after timeout.

Could you give me some advice of what might cause this problem?

Environment: SDK 14.1, SD132 V5, NRF52832

My code are based on nus example but however totally revised to implement an RTOS. And i also implement some structures from NRF52 Thingy (crossing SDK version might have some problem).

I think one of the problem might be some BLE event didn't handle properly.

Both logs above are in here

/cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-e4ead8af96f34d2cafc33581beabc35b/nexus-6.pcapng/cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-e4ead8af96f34d2cafc33581beabc35b/xiaomi-mi6.pcapng

Thanks for your time,

Jianjia

[Einar Thorsrud]

Hi Jianjia,

It is difficult to know what to make of the sniffer trace. All the packets from #362-#379 are tagged with invalid CRC, which would then result in them being correctly discarded by the SoftDevice (which in turn times out). It does not look right tough, as Wireshark seems to find the CRC field too early in the packet, which in turn is strangely long (length field is 31).

Do you have another sniffer you can compare with to see if the problem is with the sniffer or the phone?

[aircheese]

Hi, thanks for reply, I am testing with the Nexus 6 today. I am monitoring the results in NRF52 side, it seems like Nexus 6 is accepting the MTU change to 247 event it is not suppose to have anything bigger than 23. The connection then fail after this.