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WASI I2C

A proposed WebAssembly System Interface API.

Current Phase

wasi-i2c is currently in Phase 2

Champions

  • Friedrich Vandenberghe
  • Merlijn Sebrechts
  • Maximilian Seidler

Portability Criteria

WASI-I2C must have an implementation for at least the following platforms:

Platform Architecture Reference Hardware
Linux ARM Raspberry Pi 3 Model B
RTOS (NuttX or Zephyr) RISC-V ESP32-C3
RTOS (Zephyr or FreeRTOS) ARM32 Nucleo F412ZG

Furthermore, the interface should be designed in such a way to use as little memory as reasonably possible, to ensure enough RAM on these boards is still available for the applications.

Introduction

The WASI-I2C proposal defines an API for the I2C protocol. The API of embedded_hal is closely followed.

Reference implementations can be found in i2c-wasm-components. Furthermore, there is also a wasi-embedded-hal crate that implements the embedded-hal traits for the generated bindings.

Goals

The primary goal is to provide an interface that WASI programs can use to read and write data over an I2C connection.

Non-goals

Although I2C is in some aspects not that different from SPI, the purpose of this proposal is to solely focus on I2C.

API walk-through

The full API documentation can be found here.

[Walk through of how someone would use this API.]

[Use case 1]

[Provide example code snippets and diagrams explaining how the API would be used to solve the given problem]

[Use case 2]

[etc.]

Detailed design discussion

Should this be combined with SPI, GPIO and PWM into 1 embedded proposal?

Although embedded_hal takes this approach, I would keep them separated for now. At least until each proposal is at least in Phase 2.

Why are there no constructors for the i2c interface? How does one obtain an i2c handle?

I2c resources will be constructed in many different ways on different devices, so worlds that include the i2c interface should also include a way to obtain i2c handles. Typically this will either be by having i2c handles passed into exported functions as parameters, or by having i2c handles returned from imported functions.

Stakeholder Interest & Feedback

TODO before entering Phase 3.

References & acknowledgements

Many thanks for valuable feedback and advice from:

  • Merlijn Sebrechts
  • Dan Gohman for the hello-embedded repository
  • Everyone else in SIG Embedded

This work has been partially supported by the ELASTIC project, which received funding from the Smart Networks and Services Joint Undertaking (SNS JU) under the European Union’s Horizon Europe research and innovation programme under Grant Agreement No 101139067. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them. This funding supported individual contributor organisations, not the W3C or this community group as a whole.