Makoto Kawaguchi
Makoto Kawaguchi
Published: August 24, 2021

Updating an OS and application via the Internet has been a very common technology and method used in smartphones and PCs. In recent years, embedded devices also started to update firmware via the Internet, and it has been one of the important techniques for improvement in usability, such as a bug fix or adding new functions after products are released.

As many embedded devices are often not directly connected to the Internet, there are some challenges in implementing Over-the-Air (OTA) firmware updates, such as obtaining the firmware, the risk of operation stop caused by re-writing the built-in flash memory, and restrictions of the memory size.

In this blog, we are going to introduce an OTA solution that enables the firmware update using Bluetooth Low Energy (LE) on RX23W embedded devices to solve these challenges.


The RX23W OTA solution uses the popular Bluetooth LE technology to provide the function to update the firmware of RX23W embedded devices from smartphones.

This solution includes a sample program that implements the firmware update function and a sample application for smartphones to send the updated data.

The firmware update is realized by arranging the program layout, locating the Bluetooth LE protocol stack with the largest program size and the user application in different sections, and re-writing them sequentially making the best use of the memory. As each program is executed separately, the update can restart even if a power shutdown occurs during the update process.


The settings of the program section required for the firmware update for RX23W are described in the Application Note. You can easily install the firmware update function into an existing program by following the instructions in the Application Note. In addition, the sample application source code including the firmware update function is provided for users to develop a smartphone application easily.

After development

While developing the solution, we focused on making the update as easy and secure as possible, particularly trying not to make it impossible to reboot in case of an unexpected power shutdown. I think that the hurdles for introducing firmware updates by OTA to embedded devices have been lowered by the memory layout, power cutoff support, and generous application guides, so please feel free to try it!

RX23W Group Application Note: Firmware update over the air sample program
Bluetooth® Low Energy Protocol Stack for RX family

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