cannot talk to dongle after connect

[JimmyD]

I connect to the nRF52840-MDK dongle thru the Serial Terminal (nRF52 Connectivity) it found the comm port and set the baudrate automatically. However, the terminal window constantly fills up the screen with ~/ characters. it repeats every 1 second. What I would like is detailed instructions on how to configure this dongle to be a BT 5 sniffer and read the Extended Advertising for any BT device near the dongle. It would also be helpful to filter the devices seen. Eventually I like to use Python to filter the choices and obtain the advertises data where I can parse the data received. I'm using Windows 10 pro.

Thanks.

[ovrebekk]

Hi Jim

Most likely the packet containing the name and the packet containing the manufacturer data is not the same. The first packet containing the name is sent on the primary advertising channels, and this will point to a larger packet sent on one of the secondary advertising channels. The mobile app compiles all the data into one view. 

Are you able to filter on the MAC address in the Python script? Then should see all the packets from the same advertiser, and verify whether or not you can see both the packets on the primary advertising channels, and the ones on the secondary advertising channel. 

Best regards
Torbjørn

[JimmyD]

Since I'm new to Bluetooth, I'll have to research this. I knew that there were channels but I haven't understood fully what they were used for or how to get that information.

Yes,  I can specifically state what MAC address to look for.

[ovrebekk]

Hi 

We provide various online courses as part of the Nordic Developer Academy, and we recently released a specific module for Bluetooth which you might want to check out:
https://www.nordicsemi.com/Support/Nordic-Developer-Academy

The short story is that Bluetooth LE uses 40 dedicated RF channels, 3 of which are designated as primary advertising channels. 

These three channels will be used for advertising only, and legacy (non extended) advertising are limited to these channels exclusively. 

The remaining 37 channels were originally only used for devices in a connection, until the extended advertising feature was introduced in v5 of the Bluetooth specification. 

An extended advertiser will essentially send a small packet on one of the primary advertising channels which contains little data, but points to a larger packet on one of the remaining 37 channels containing the payload. This means that you can advertise a large amount of data without congesting the 3 primary advertising channels, which have to be shared between all Bluetooth LE devices. 

One drawback of this mechanism (that you have to get around now) is that you need to be able to receive both the small packet sent first on one of the primary advertising channels, and the second packet sent on one of the remaining 37 channels, in order to get all the information from the advertiser. 

Best regards
Torbjørn

[JimmyD]

Thanks for that information, it was very useful. I'm hoping that I'll have some time soon to view the course.

Your response leads me to my next question; Is there a way I can get the information I'm looking for using your dongle? and if so how can I modify the python code to do that?

I guess what I'm asking is how to get the information on the remaining 37 channels using your dongle and the python code?

I think the answer may be in the Sniffer.py file. I just can't pin point where.

[JimmyD]

Torbjørn,

I need to know how to do this in Python. Can you help?

(I need to be able to receive both the small packet sent first on one of the primary advertising channels, and the second packet sent on one of the remaining 37 channels, in order to get all the information from the)

Thanks.

Jimmy D.