Enable logging for nRf52840 dongle(PCA10059)

[Appugowdac]

Enable logging for nRf52840 dongle(PCA10059)
Appugowda C
Online
Appugowda C
23 hours ago
I have a requirement where I'm using a .NET-based test adapter that communicates using the Modbus protocol over a serial (COM) port.

Now, I want to develop a BLE Central device using the nRF52840 Dongle (PCA10059), which will communicate with other BLE Peripheral devices. The idea is to send Modbus commands from the .NET test adapter (via COM port) to the nRF52840 dongle, and the dongle will handle BLE operations accordingly.

At the same time, I want to be able to view log outputs from the dongle in parallel (e.g., to another COM port).

My Questions:
Is it possible to achieve Modbus communication and logging simultaneously using the nRF52840 dongle without any hardware modifications (e.g., without soldering to UART pins)?

If yes, could you please guide me on how to implement this? Specifically:

How to expose two virtual COM ports over USB (e.g., using two USB CDC ACM instances)?

How to route one COM port for Modbus commands and another for logs (e.g., using LOG_INF()).

Any example project or modifications to existing samples to support this use case.

SDK: nRF connect SDK v2.9.0
Toolchain : nRF connect SDK Toolchain v2.9.0
Board target : nrf52840dongle/nrf52840
Selected Nordiac SoC
zephyr version was v2.9.0

Looking forward to your guidance.

Thank you!

[github-actions[bot]]

Hi @Appugowdac! We appreciate you submitting your first issue for our open-source project. 🌟

Even though I'm a bot, I can assure you that the whole community is genuinely grateful for your time and effort. 🤖💙

[jfischer-no]

There is an example that shows how to use the CDC ACM and Modbus server, https://docs.zephyrproject.org/latest/samples/subsys/modbus/rtu_server/README.html#using-cdc-acm-uart

nRF52840 Dongle uses CDC ACM serial by default for logging and console, so you will see two CDC ACM devices connected to your host, one for logging and one for Modbus communication.

Please read the documentation first for all future questions, https://docs.zephyrproject.org/latest/introduction/index.html

[Appugowdac]

I have reviewed both the documentation and your links, but I am facing some roadblocks and would really appreciate some more detailed guidance
Any clarification or deeper instructions for dual-CDC composite USB on this hardware and NCS version would be extremely appreciated. I want to get both Modbus communication and logs in parallel, on two separate USB virtual COM ports, using only the built-in USB of the nRF52840 Dongle, and no hardware modifications.
My scenario (rephrased for clarity):
Board: nRF52840 Dongle (PCA10059)
SDK: nRF Connect SDK v2.9.0 / Zephyr v3.x

Host: Windows with a .NET test adapter

• One for Modbus comms (from .NET → Dongle → BLE ↔ Peripheral)
• One for logs/console messages for development/debug

I am NOT asking about Arduino or native serial/UART hardware, only about using the native USB CDC ACM(s) provided by the dongle.

Any clarification or deeper instructions for dual-CDC composite USB on this hardware and NCS version would be extremely appreciated. I want to get both Modbus communication and logs in parallel, on two separate USB virtual COM ports, using only the built-in USB of the nRF52840 Dongle, and no hardware modifications.
Thank you so much for your support!