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msp430

Low level access to MSP430 microcontrollers

This crate is based on cortex-m crate by Jorge Aparicio (@japaric).

This crate requires a nightly rust due to the use of the new asm! (0.3.0 and above), llvm_asm! (0.2.2) or old asm! (0.2.1 and below) macros. The below table contains compilers which are known to work:

msp430 versionrustc compiler
0.3.0nightly-2022-01-24
0.2.2nightly-2020-04-22
0.2.1nightly-2020-01-04

Features

The critical-section-single-core feature provides a critical section implementation based upon disabling interrupts.

Critical sections by disabling interrupts are a valuable way to access I/O and shared data safely in msp430. However, rustc/LLVM does not always optimize critical sections well in terms of space. For example, sometimes rustc/LLVM will create two copies of interrupt enable assembly code when exiting a critical section that contains a branch- one copy each for branch-taken/branch-not-taken.

This crate provides three features for giving hints to rustc/LLVM for how to optimize critical sections for size. Both critical_section::with and the interrupt::free critical sections are supported, with and without the critical-section feature above:

If saving space is a concern in your application, you should experiment with which features provide the best size savings and balance this against the execution overhead of the extra function calls due to outlining. The execution overhead of enabling each hint is ~5 + 2 clock cycles for each critical section- at least a CALL and RET instruction.

Documentation

License

Licensed under either of

at your option.

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 dual licensed as above, without any additional terms or conditions.