Link layer Packet

[Stayhungry]

When I use sniffers and wireshark for debugging (ble_app_uart), I found a strange place.

The following are the empty data PDUs seen from wireshark:

50ms:

Master->Slave

Slave-> Master

Master-> slave

Slave-> Master

...

..

7.5ms:

Slave-> Master

Slave-> Master

Slave-> Master

As shown above, interval is set to 50ms are normal, but when I updated the interval to 7.5ms, which is the Slave initiates the L2CAP layer parameter update request, it will happen Slave continuous sending multiple LL packet, check each PDUs, they Data PDU header is the same, even the CRC are the same, the only difference is that capture RF channel is not the same.

Is this a normal phenomenon? According to my understanding of BLE Core, it should be the Master sent a packet, and then Slave backpack, is my understanding wrong?

[Petter Myhre]

Not normal, could you edit your question and upload the sniffer trace file?

[Stayhungry]

Thank you very much for your reply. I changed a computer to run the same version of sniffer and wireshark can correctly capture the package, whether it is 7.5ms or 50ms, I suspect that my previous computer configuration a bit low.

By the way, if there is only one connection, and the event length is set to 6 (1.25 * 6 = 7.5ms) in sdk_config.h, if I want to be able to send 6 LL PDUs in a connection event, some other configuration is needed ? Or the hardware automatically?

[Petter Myhre]

Depends one what peer you are connecting to, chipset you are using, SoftDevice you are using, SDK you are using, example you are using. Please provide some more information. An event length of 6 doesn't mean 6 packets, it means that 7.5 ms of the connection interval is reserved for this particular link.

[Stayhungry]

Thanks Petter.

This is another question, I created another question, not here

[Petter Myhre]

Ok. Maybe you can accept this one then?