RTIC

Real-Time Interrupt-driven Concurrency

A concurrency framework for building real-time systems

Preface

This book contains user level documentation for the Real-Time Interrupt-driven Concurrency (RTIC) framework. The API reference is available here.

Formerly known as Real-Time For the Masses.

This is the documentation of v1.0.x of RTIC; for the documentation of version

Is RTIC an RTOS?

A common question is whether RTIC is an RTOS or not, and depending on your background the answer may vary. From RTIC's developers point of view; RTIC is a hardware accelerated RTOS that utilizes the NVIC in Cortex-M MCUs to perform scheduling, rather than the more classical software kernel.

Another common view from the community is that RTIC is a concurrency framework as there is no software kernel and that it relies on external HALs.

crates.io docs.rs book matrix Meeting notes

Features

  • Tasks as the unit of concurrency 1. Tasks can be event triggered (fired in response to asynchronous stimuli) or spawned by the application on demand.

  • Message passing between tasks. Specifically, messages can be passed to software tasks at spawn time.

  • A timer queue 2. Software tasks can be scheduled to run at some time in the future. This feature can be used to implement periodic tasks.

  • Support for prioritization of tasks and, thus, preemptive multitasking.

  • Efficient and data race free memory sharing through fine grained priority based critical sections 1.

  • Deadlock free execution guaranteed at compile time. This is a stronger guarantee than what's provided by the standard Mutex abstraction.

  • Minimal scheduling overhead. The task scheduler has minimal software footprint; the hardware does the bulk of the scheduling.

  • Highly efficient memory usage: All the tasks share a single call stack and there's no hard dependency on a dynamic memory allocator.

  • All Cortex-M devices are fully supported.

  • This task model is amenable to known WCET (Worst Case Execution Time) analysis and scheduling analysis techniques.

Crate cortex-m 0.6 vs 0.7 in RTIC 0.5.x

The crate cortex-m 0.7 started using trait InterruptNumber for interrupts instead of Nr from bare-metal. In order to preserve backwards compatibility, RTIC 0.5.x will keep using cortex-m 0.6 by default. cortex-m 0.7 can be enabled using the feature cortex-m-7 and disabling default features:

cortex-m-rtic = { version = "0.5.8", default-features = false, features = ["cortex-m-7"] }

RTIC 1.0.0 already uses cortex-m 0.7 by default.

User documentation

Documentation for the development version.

API reference

Community provided examples repo

Chat

Join us and talk about RTIC in the Matrix room.

Weekly meeting notes can be found over at HackMD

Contributing

New features and big changes should go through the RFC process in the dedicated RFC repository.

Running tests locally

To check all Run-pass tests locally on your thumbv6m-none-eabi or thumbv7m-none-eabi target device, run

$ cargo xtask --target <your target>
#                       ˆˆˆˆˆˆˆˆˆˆˆˆ
#                   e.g. thumbv7m-none-eabi

Acknowledgments

This crate is based on the Real-Time For the Masses language created by the Embedded Systems group at Luleå University of Technology, led by Prof. Per Lindgren.

References

1

Eriksson, J., Häggström, F., Aittamaa, S., Kruglyak, A., & Lindgren, P. (2013, June). Real-time for the masses, step 1: Programming API and static priority SRP kernel primitives. In Industrial Embedded Systems (SIES), 2013 8th IEEE International Symposium on (pp. 110-113). IEEE.

2

Lindgren, P., Fresk, E., Lindner, M., Lindner, A., Pereira, D., & Pinho, L. M. (2016). Abstract timers and their implementation onto the arm cortex-m family of mcus. ACM SIGBED Review, 13(1), 48-53.

License

All source code (including code snippets) is licensed under either of

at your option.

The written prose contained within the book is licensed under the terms of the Creative Commons CC-BY-SA v4.0 license (LICENSE-CC-BY-SA or https://creativecommons.org/licenses/by-sa/4.0/legalcode).

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.