WASM Embedded

WASM on Embedded Systems (RTOS)

Real-Time Operating System

Han Wu, University of Exeter, the UK

Source Code

C/C++ Libraries
(OpenCV, Eigen, etc)

Chrome V8 (WASM Runtime)

Chrome (V8 Runtime)

Intel i7 (1.9GHz) - 16GB RAM

ARM Linux (WASM3 Runtime)

Cortex-A7 (1.2GHz) - 64MB RAM

RT-Thread (WAMR Runtime)

Cortex-M4 (120MHz) - 640KB RAM

Arduino (WASM3 Runtime)

ESP32 (240MHz) - 520KB RAM

Embedded Systems have very limited hardware resources. For example, a web browser may consume a lot of memory and CPU resources. For a laptop, it is very common to have 16GB of memory. What if we only have 64MB of memory and a slower ARM CPU. In this case, we need a different WASM runtime, which runs on ARM Linux and does not need a browser. Now, we can run the same WASM code on ARM Linux, or Embedded Linux.

However, ARM Linux is still Linux, what if we only have 640KB of Memory? We don't even have sufficient memory to run Linux. And the CPU is so much slower, it runs at 120MHz, rather than 1.2GHz. To solve this problem, we have WASM Micro-Runtime that runs on Real-time Operating System, such as Zephyr, RT-Thread, FreeRTOS, etc. Now we have WASM on Embedded Systems. For this demo application, I used RT-Thread, an open-source Real-time Operating System.

And the last one, Arduino, which is an open-source hardware and sorftware platform. We can run WASM on even smaller devices.

This is how we use WASM on different platforms. Basically, we use different WASM runtime to run the WASM code.

GUI (HDMI, LCD)

wasi-filesystem

wasi-sockets

wasi-digital-io

wasi-i2c

wasi-spi

Web Assembly System Interface (WASI) Support

If we look at the WASM code. Basically, it performs some computation and stores the data to the memory. If we send the memory to a screen, we see the image. But for embedded systems, comprated with the Graphic User Interface, we care more about access to the hardware, such as the filesystem, web sockets, gpio, i2c and spi communication bus, so that we can interact with different sensors. This is one of the major differences between using WASM in the browser and WASM on embedded systems. For embedded systems, we need access to the low-level hardware.

This problem can be solved using WASM System Interface, or WASI.

Another benefit of using WASM is that it supports different programming languages. For example, we can compile C/C++, Rust and Golang to WASM code. We can use different programming languages to develop WASM applications.

Here's a summary of the hardware, runtime, and programming languages I used in this project.

Thanks

https://wasm-embedded.wuhanstudio.uk

Source Code