Packet length and number of packets transmitted.

[Capoxi]

In the software NRf Connect Desktop.

The packet length (bytes) variable. What part of the Bluetooth packet does this change.

How does one calculate the number of transmitted packet given. LE 1M, Update period, Timeout, PRBS9 & packet length. 

[Hung Bui]

Hi Kujtim, 

Could you give some more information about the packet length varied ? 

Maybe some log ? 

I think the easiest way to breakdown BLE packet is to use the nRF Sniffer to capture the actual packets over the air.

[Capoxi]

The situation is DTM testing with NRF Connect Desktop

[Hung Bui]

Hi Kujtim, 
The best way to get to understand the DTM is to read about the DTM protocol in Bluetooth Core Spec. 
You can find it at chapter 4 Part F Vol 6. 

You can also have a look at the DTM firmware in the SDK (\examples\dtm\direct_test_mode\) it's the firmware flashed on the nRF52 when you test with the nRF Connect DTM app. The DTM app on PC is only the frontend that talk to the DTM firmware on nRF52 via UART.

To answer your question, the packet length is the length of they dummy payload 

The interval between packet is calculated inside dtm_packet_interval_calculate() function in ble_dtm.c (in the dtm firmware in the SDK) and you can read about how to calculate it at  Vol. 6 Part F Section 4.1.6 in Bluetooth core spec.

[Capoxi]

Thanks for the reading suggestion.

Found also this:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/direct_test_mode/README.html

Followed by this information.

Bluetooth Core Specification: Version 5.2, Vol. 6, Part F. Searching for this lead to a 3k+ page document with the information i searched for.

Thanks Hung 

[Hung Bui]

Hi Kujtim,

Great that you found the documentation for DTM. Regarding the Bluetooth Core Spec, it's 3000+ page, but if you go to Vol 6 Part F Chapter 4 you can find the DTM protocol defined there :)