21. December 2022

Rust Bare Metal application for ESP32, desktop, Android and iOS

Rust language and tooling are very powerful. It makes it easy to build for different platforms and architectures and still have performance close to C language.

It’s possible to write the same application for ESP32 with Xtensa architecture or ESP32-C3 RISC-V architecture. The portability of Rust code is high. Changing the target and adding a few wrapper functions makes it possible to build the same application for the desktop or web browser with WebAssembly. Once the WebAssembly is ready, it’s possible to turn the application into Progressive Web App (PWA) which can be installed on Android or iOS.

ESP32 Spooky Maze game is example of application which can work on ESP32 and also on mobile device. The shared core code contains the main part of the implementation, and each platform has its tiny wrapper.

The example Rust application uses Embedded Graphics to draw images. When the app is running on real HW, it’s transferred to the display via SPI using ESP-HAL. The desktop version is using SDL2 to interact with Linux, macOS, or Windows. The web version is using WASM, and framebuffer is serialized to HTML5 canvas. PWA application for Android also supports access to Accelerometer, so it can simulate similar behavior like IMU on ESP32-C3-DevKit-RUST or ESP32-S3-BOX where user can tilt the device to move the character in the maze.

Web version of the application with PWA support: Spooky (full-screen mode)

Embedded version of the application: ESP32-S3-BOX, M5CORE-FIRE (M5Stack) and many more.

Thanks to cloud development IDEs, it’s possible to build the application on GitPod.io or GitHub Codespaces and run it even without real HW using Wokwi simulator.

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22. October 2017

SDL2_image for iOS with JPEG image format

Adding SDL2_image with JPEG support for iOS is a little bit different than for Android. In case of Android, it was necessary to add JPEG library in C and build it. iOS has JPEG dependency hidden in another library which is already compiled in frameworks.

If you just add SDL2_image to your project for iOS, you will very likely end up with following linker error:

"_kUTTypeJPEG", referenced from ...
Linker command failed with exit code 1

To resolve this issue, it is sufficient to add two dependencies into your project.

Go to Project and select Build Phases.

In the section Linking add library: ImageIO.framework

Then add the second dependency: MobileCoreServices.framework

Then Clean and Build the project.

These steps should resolve the linker issue, and JPEG should work.

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