Bootloader Fails to upgrade via BLE

Hello to all…

I was trying to run a simple temp+Humidity example sketch which was not working. I explored what could be issue and it seems it does not start the sketch as nothing apears on serial monitor. So found another person that has similar issue and that resolution was found with bootloader upgrade to 0.4.1.

This is where my issue starts…I can only upgrade via BLE as i do not have other means. I have tried nRF Toolbox and nRF Connect, both fail. I have tried Updated bootloader for RAK4631
Still no candy. The unit seems to reboot prior to getting update. I am using an Apple Phone hopefully that is not the issue
Thanks for any guidance

Hello @Lucatz
Welcome to the forum.

Do you have a PC or laptop available for the bootloader update? If yes, which operating system? Windows, Linux or MacOS?

We found a possibility to update the bootloader over USB cable, but to be able to send you the correct instructions I need to know which operating system your PC has.

Updating the Bootloader

RAK4631 WisBlock Core is programmed with USB bootloader so that you can upload application firmware to it without using any exernal tools like Jlink and other programmers/debuggers. However, there are situations that you need to update the bootloader when there is an updated version that supports new features, improvements and bug fixes.

There are various ways to update the bootloader like via USB, Bluetooth and Jlink. The procedure on these methods are explained in this guide.

Bootloader update via USB

On this method, you need to two things:

  1. Adafruit-nrfutil utility program.
  2. RAK4631 Bootloader FW.
For Windows

Download the adafruit-nrfutil.exe and the latest RAK4631 bootloader firmware

Once you downloaded these files, you need to put them on a same directory/folder in your computer.

For simplicity, this guide will assume the files are in C: drive.

When the files are ready, you need to open Windows Command Prompt application. Then you need to change the location to C:.

cd C:\

After that, you can now execute the update using this command.

adafruit-nrfutil.exe --verbose dfu serial --package --port COM8 -b 115200 --singlebank --touch 1200

You need determine if the right COM port number of your device. COM8 on the command above is only for illustration. You will have error if you are not connected to the right COM port number.

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For Linux

You can get and install adafruit-nrfutil via pip3.

sudo pip3 install adafruit-nrfutil


pip3 install --user adafruit-nrfutil

Then you need to download the latest RAK4631 bootloader firmware

Open the terminal and go to the directory where the RAK4631 Bootloader FW is located.

Then you need to execute this command:

adafruit-nrfutil --verbose dfu serial --package -p /dev/ttyACM0 -b 115200 --singlebank --touch 1200

For macOS

Same with Windows and Linux procedures, you need to download the latest RAK4631 bootloader firmware.

There are two ways to update the RAK4631 bootloader in macOS.

If you have Python installed, you can follow the same steps for Linux.

Another way is by creating a macOS executable. To do this method, you need to download adafruit-nrfutil-macos and make it executable.

Usually, the adafruit-nrfutil-macos file will go to the downloads folder.

The next step after downloading the file is to open the terminal and go to the downloads directory or the location where you put the downloded file.

cd /Users/username/Downloads

And then execute this command:

chmod +x adafruit-nrfutil-macos


You also need to determine the port name of the RAK4631 using the command:

ls /dev/cu.*.


After all this steps, you can now upload the latest RAK4631 Bootloader Firmware by executing this command:

adafruit-nrfutil-macos --verbose dfu serial --package -p /dev/cu.usbmodem411 -b 115200 --singlebank --touch 1200


Your RAK4631 will now have the updated Bootloader Firmware.

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How to Check if You Have the Updated RAK4631 Bootloader

You need to connect the RAK4631 to PC via USB cable and double click reset button on the WisBlock Base.

There will be a new drive named RAK4631 that will be shown on your folder explorer. Inside this drive, there will a text file named INFO_UF2.TXT as shown in Figure 15.

If you open INFO_UF2.TXT, you’ll see Date: Mar 31 2021 as shown in Figure 16.


If you have a differet drive name or older date, it means you do not have the updated RAK4631 Bootloader and you need to update it.

Works Perfectly
Thank you Beegee! :smiley:

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