Setup nRF52 dongle as a Central BLE device and relay all the data from the peripheral to the PC via USb port

[exsurgo_ankit]

Hello,

As per the title, I am trying to use the nRF52 dongle to interface with our device which uses nRF52 based module. The idea is to communicate with the dongle over USB port and send data to our device and receive data back.

Essentially, the nRF52 dongle is replacing the PC's built in Bluetooth which can be sometimes unreliable. Also enables us to have multiple dongles connected to communicate with multiple BLE devices simultaneously.

So I downloaded the Bluetooth: CENTRAL UART WITH USB_CDC_ACM source from github.

https://github.com/WesC-sys/usb_dongle

As suggested in this older ticket.

 Using the nRF52840 Dongle (PCA10059) as a USB serial-to-BLE port 

The issue I face is that the USBD write to the PC is not buffered and drops bytes. Is there a reliable way to implement what I am trying to achieving with high data throughput as out device uses data length extensions and transmits 200 bytes every 30 milliseconds.

Would it better to use a nrf52 DK and a USB UART to achieve the above?

Regards

[Einar Thorsrud]

Hi,

I do not see any problems with sending 200 bytes every 30 ms or so, and using long ATT MTU and data length extension you can do this in single packets.

The project you found there is quite old and based on the old SoftDevice, so I would avoid that if possible. The nRF Connect SDK also has NUS samples. You could use the Bluetooth central UART sample, but refer to the Bluetooth peripheral UART sample for the USB CDC part. I would also refer to configs from the throughput sample prj.conf for buffer sizes etc so you get long packets.

[exsurgo_ankit]

Hello Einar,

Thank you for the suggestions. Why would you avoid the old soft device? Our product has been developed on the old soft device and has been running well for over 5 years. It does not use USB CDC. Is the USB CDC not reliable?

When I use the Bluetooth Low Energy app in nRF Connect for Desktop, it programs the dongle and I can control it just the way I need to. The issue, is that I can't find the firmware source for the application and the Electron JS source for the desktop app seems difficult to traverse for me to understand what commands are being sent.

I would be happy to just use the dongle with that app's firmware, if I knew the commands it was sent to scan, connect and subscribe to characteristics. Kind of like what the PC Bluetooth drivers enable me to do. Is this information (commands sent to nRF dongle by the BLE app in nRF Connect) available in the public domain.

Regards

[lammobile]

Hi exsurgo_ankit,

Have you tried it? 
github.com/.../pc-ble-driver

[exsurgo_ankit]

Hello, I did stumble across this. However, it is unclear how I can write an application on PC that will communicate with the dongle running this firmware and allow me to scan, connect and subscribe to characteristics.

The documentation has an architecture image that is missing, which might have made it clearer. 

If you have successfully used the pc-ble-driver for something similar to my application then please suggest at a high level how did you accomplish it.

[lammobile]

Hi exsurgo_ankit, 

You can follow the user guide in README file.

1. Compiling connectivity HEX files (for nRF chip)
2. Programming connectivity HEX files (for nRF chip)
or 

How to Compile the Ble_Connectivity hex and Run with nRF Connect Desktop

3. Run app on PC with Visual Studio after Compiling pc-ble-driver on Windows

[exsurgo_ankit]

Hello,

Does this mean that nrf_ble_desktop is the PC application?

Ble Connectivity firmware is already being programmed by nRF Connect on the dongle.

I will ask a different question, as your response does not clearly state how to achieve my objective.

I want to know how and what commands need to be sent to the ble connectivity firmware so I can create a PC app using any programming language to open a USBD virtual com port, and send commands to scan, connect and communicate with the peripheral.

[lammobile]

Let me describe how I experimented:

nRF peripheral: heart rate example
nRF central (dongle): connectivity HEX files firmware
PC: running github.com/.../main.c

This main.c program will communicate with the nRF central (dongle) to scan, connect, and read heart rate values from the nRF peripheral (TARGET_DEV_NAME "Nordic_HRM").

PC <-- USB_CDC_ACM --> nRF central          <------ BLE packet --->  nRF peripheral.

Apologies if my experiment differs from your requirements.