AirTurn firmware redevelopment

Background & brief

AirTurn had an existing lineup of products compatible with Bluetooth 4.0 LE, initially developed by NRB Tech several years ago. In order to support new features and Bluetooth 5.0 the next generation of AirTurn would require a new hardware platform, which would mean the firmware would need to be rewritten. As the existing platform was very mature and feature rich, this would be a significant undertaking.

AirTurn wanted to ensure that the re-written code would last a long time, and be portable across future hardware platforms. AirTurn also has Apps for macOS, iOS and Android, with perhaps more platforms in the future. There was common functionality across all these platforms, particularly around the communication of data between Apps and firmware. Therefore it was hoped that there could be increased code sharing between platforms.

Our Approach

As the existing developer of AirTurn’s firmware, iOS and macOS Apps, and iOS SDK, NRB Tech was deeply familiar with the requirements of the redevelopment and the cross platform requirements for any code sharing. We worked with AirTurn to understand both present and future needs, and met with AirTurn and hardware manufacturers to determine the best hardware platform for the redevelopment. We looked at the existing code bases to determine how much of it could easily be shared between platforms.

The solution

The redevelopment was undertaken in multiple stages. Initially a shared C library was created to extract as much shared logic as possible from the Apps and firmware. Several hundred unit tests were written to ensure this code was reliable, then the existing App logic was replaced with the new library, and App updates were released to the relevant stores.

The next stage was to rewrite the firmware logic in a platform independent manner, integrating the shared C library. The logic was completely abstracted from the hardware with a platform abstraction layer. To make initial testing easier the library was integrated into a macOS App, and the hardware layer written for macOS, complete with a user interface which replicated the hardware. This greatly reduced development time. In addition, hundreds of unit tests were written for the firmware logic.

Finally the hardware layer for the selected hardware platform was written and testing undertaken. This resulted in a firmware that was solid from the first build, and required very minimal modification to get production ready.