Quick Start Guide: nRF52840 Dongle Firmware Development

The nRF52840 Dongle (PCA10059) is a cost-effective USB development board perfect for prototyping BLE, Zigbee, and Thread applications. Since it does not feature an onboard J-Link debugger, the development workflow differs slightly from standard Nordic Development Kits (DKs).

This guide outlines the standard workflow based on macOS and the nRF Connect SDK (NCS): Build -> Generate DFU Package -> USB Flashing.

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1. Environment Preparation

Essential Tools

1. nRF Connect for Desktop: Download from Nordic Official Site. After installation, it is recommended to add the Programmer and Serial Terminal apps.
2. nrfutil: Required for packaging and flashing firmware.

   pip3 install nrfutil

3. nRF Connect SDK: Recommended to install via the VS Code Extension (“nRF Connect for VS Code”) for a one-click setup of the SDK and Toolchain.

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2. Minimal Project Configuration (Hello World)

We will create a minimal project that supports the USB Virtual Serial Port (CDC ACM).

prj.conf (Key Configuration)

# Enable USB Stack and CDC ACM Class
CONFIG_USB_DEVICE_STACK=y
CONFIG_USB_CDC_ACM=y
# Redirect console to USB Serial
CONFIG_SERIAL=y
CONFIG_UART_CONSOLE=y
CONFIG_CONSOLE=y
CONFIG_UART_LINE_CTRL=y
# Logging Configuration
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=3

src/main.c

#include <zephyr/kernel.h>
#include <zephyr/usb/usb_device.h>
#include <zephyr/drivers/uart.h>
#include <zephyr/logging/log.h>

LOG_MODULE_REGISTER(main);

void main(void) {
    const struct device *dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
    uint32_t dtr = 0;

    if (usb_enable(NULL)) return;

    /* Wait for host to connect to serial port (DTR set) */
    while (!dtr) {
        uart_line_ctrl_get(dev, UART_LINE_CTRL_DTR, &dtr);
        k_sleep(K_MSEC(100));
    }

    int count = 0;
    while (1) {
        LOG_INF("Hello Dongle! Count: %d", count++);
        k_sleep(K_SECONDS(1));
    }
}

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3. Build and Package

3.1 Build

In VS Code, add a Build Configuration. Select nrf52840dongle_nrf52840 as the Board, then click Build.
Alternatively, use the command line:

west build -b nrf52840dongle_nrf52840

The build artifact is located at build/zephyr/zephyr.hex.

3.2 Generate DFU Package

The Dongle can only be updated via its Bootloader. The .hex file must be packaged into a .zip archive:

nrfutil pkg generate --hw-version 52 --sd-req 0x00 \
  --application build/<your_project_name>/zephyr/zephyr.hex \
  --application-version 1 app.zip

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4. Enter DFU Mode and Flash

Enter DFU Mode

1. Press the sideways Reset button.
2. Insert the Dongle into a USB port.
3. Release the button. The Red LED should pulse, indicating DFU mode is active.

Flash Firmware

1. Find Device Port:

   ls /dev/tty.usbmodem*
   # Example Output: /dev/tty.usbmodemXXXX

2. Flash:

   nrfutil dfu usb-serial -pkg app.zip -p /dev/tty.usbmodemXXXX

   Note: Replace the port number in the command with the actual one observed.

Upon successful flashing, the device will automatically reboot and run the new firmware.

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5. FAQ

• Q: Flashing fails with No DFU devices found
  • A: Ensure the Red LED is pulsing (DFU mode). Verify the port number (the port in DFU mode may differ from the application runtime port).
• Q: No output on Serial Port
  • A: The serial tool must enable the DTR signal (the code waits for DTR). We recommend using the Serial Terminal in nRF Connect for Desktop, which handles DTR automatically.
• Q: nrfutil command not found
  • A: Ensure the Python bin directory is in your system PATH.

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6. Advanced References

• Custom LED: Use an .overlay file to modify the Device Tree.
• Reduce Firmware Size: Add CONFIG_SIZE_OPTIMIZATIONS=y to prj.conf.
• Official Documentation: nRF52840 Dongle User Guide