Crate cortex_m

source ·
Expand description

Low level access to Cortex-M processors

This crate provides:

  • Access to core peripherals like NVIC, SCB and SysTick.
  • Access to core registers like CONTROL, MSP and PSR.
  • Interrupt manipulation mechanisms
  • Safe wrappers around Cortex-M specific instructions like bkpt

Optional features


When this feature is enabled the implementation of all the functions inside the asm and register modules use inline assembly (asm!) instead of external assembly (FFI into separate assembly files pre-compiled using arm-none-eabi-gcc). The advantages of enabling inline-asm are:

  • Reduced overhead. FFI eliminates the possibility of inlining so all operations include a function call overhead when inline-asm is not enabled.

  • Some of the register API only becomes available only when inline-asm is enabled. Check the API docs for details.

The disadvantage is that inline-asm requires a Rust version at least 1.59 to use the asm!() macro. In the future 0.8 and above versions of cortex-m, this feature will always be enabled.


This feature enables a critical-section implementation suitable for single-core targets, based on disabling interrupts globally.

It is unsound to enable it on multi-core targets or for code running in unprivileged mode, and may cause functional problems in systems where some interrupts must be not be disabled or critical sections are managed as part of an RTOS. In these cases, you should use a target-specific implementation instead, typically provided by a HAL or RTOS crate.


This feature enables workarounds for errata found on Cortex-M7 chips with revision r0p1. Some functions in this crate only work correctly on those chips if this Cargo feature is enabled (the functions are documented accordingly).


This feature links against prebuilt assembly blobs that are compatible with Linker-Plugin LTO. This allows inlining assembly routines into the caller, even without the inline-asm feature, and works on stable Rust (but note the drawbacks below!).

If you want to use this feature, you need to be aware of a few things:

  • You need to make sure that -Clinker-plugin-lto is passed to rustc. Please refer to the Linker-Plugin LTO documentation for details.

  • You have to use a Rust version whose LLVM version is compatible with the toolchain in asm-toolchain.

  • Due to a Rust bug in compiler versions before 1.49, this option does not work with optimization levels s and z.

Minimum Supported Rust Version (MSRV)

This crate is guaranteed to compile on stable Rust 1.38 and up. It might compile with older versions but that may change in any new patch release.


pub use crate::peripheral::Peripherals;


Miscellaneous assembly instructions
Cortex-M Security Extensions
A delay driver based on SysTick.
Instrumentation Trace Macrocell
Core peripherals.
Processor core registers


Macro for sending a formatted string through an ITM channel
Macro for sending a formatted string through an ITM channel, with a newline.
Macro to create a mutable reference to a statically allocated value