nRF52 Device Flashing Guide

Overview

This guide will walk you through flashing custom firmware to your nRF device (nRF52840, nRF52832, etc.) using the UF2 firmware files downloaded from MeshForge.

Prerequisites

  • Custom firmware built and downloaded from MeshForge
  • nRF device (nRF52840, nRF52832, or compatible)
  • USB cable to connect your device to your computer

Step-by-Step Instructions

1. Build and Download Firmware

  1. Build your custom firmware for your nRF device on meshforge.org
  2. When the build completes, download the compressed firmware archive (.tgz file)

2. Extract Firmware Files

Extract the downloaded .tgz archive to a folder. You should see the following files:

  • firmware.uf2 - UF2 firmware file (this is what you'll flash)
  • firmware.elf - ELF debug file (not needed for flashing)

Note: The firmware.uf2 file is the main file you need for flashing.

3. Enter DFU Mode

Your nRF device needs to be in DFU (Device Firmware Update) mode before flashing. The method varies by device:

Common Methods:

  • Double-tap reset button: Quickly press the reset button twice in succession
  • Button combination: Hold the BOOT/DFU button while pressing and releasing RESET
  • Specific device instructions: Some devices have unique methods (check your device documentation)

Verify DFU Mode:

When successfully in DFU mode, you should see:

  • A new USB drive appear on your computer (typically named "DFU" or similar)
  • The device LED may change behavior (blinking pattern or solid color)
  • The device will not appear as a serial port

4. Flash the Firmware

  1. Locate the USB drive: Open your file manager and find the DFU drive that appeared when you entered DFU mode
  2. Copy the UF2 file: Drag and drop (or copy) the firmware.uf2 file onto the DFU drive
  3. Wait for completion: The device will automatically begin flashing. You may see the drive activity indicator or LED changes
  4. Automatic reboot: Once flashing completes, the device will automatically reboot and exit DFU mode

5. Verify the Flash

After the device reboots:

  • The DFU drive should disappear from your computer
  • The device should appear as a serial port (if applicable)
  • Your device should now be running the custom firmware

Troubleshooting

Device Not Entering DFU Mode

  • Try different button combinations: Some devices require specific timing or button sequences
  • Check device documentation: Your specific device may have unique DFU entry requirements
  • Ensure USB connection: Make sure the USB cable supports data transfer (not just charging)

DFU Drive Not Appearing

  • Check device manager: On Windows, verify the device is recognized
  • Try different USB port: Some USB ports may not work properly
  • Install drivers: Some devices require specific USB drivers (check manufacturer documentation)
  • Try different cable: Faulty cables can prevent proper communication

Flash Fails or Device Won't Boot

  • Verify firmware compatibility: Ensure the firmware matches your exact device model
  • Try re-entering DFU mode: Sometimes the device needs to be reset and DFU mode re-entered
  • Check file integrity: Re-download the firmware file to ensure it wasn't corrupted
  • Use erase option: Some devices may need to be erased before flashing (check device-specific instructions)

Device Stuck in DFU Mode

  • Disconnect and reconnect: Unplug the USB cable and plug it back in
  • Hard reset: Some devices have a hard reset method (check device documentation)
  • Re-flash bootloader: In extreme cases, the bootloader may need to be reflashed using a debugger

Additional Notes

  • Firmware versions: Always ensure you're flashing firmware compatible with your device model
  • Backup: If possible, keep a backup of your working firmware before flashing new versions
  • Multiple devices: If flashing multiple devices, ensure each is in DFU mode before copying the UF2 file

Device-Specific Information

Different nRF devices may have slight variations in the flashing process. Common nRF devices include:

  • nRF52840: Most common, supports UF2 bootloader
  • nRF52832: Older generation, may require different methods
  • Adafruit nRF52840 Feather: Uses double-tap reset for DFU mode
  • Seeed XIAO nRF52840: Typically uses double-tap reset
  • RAK4631: May use different button combinations

Check your specific device documentation for exact DFU entry procedures.