defmt

defmt ("de format", short for "deferred formatting") is a highly efficient logging framework that targets resource-constrained devices, like microcontrollers.

For more details about the framework check the book at https://defmt.ferrous-systems.com.

Components

This repository contains the following packages:

Name	Path	Description
defmt	./defmt	On-target code for highly efficient logging
defmt-macros	./macros	Proc Macros for defmt
defmt-print	./print	CLI utility for decoding and printing defmt encoded logs to standard out
defmt-decoder	./decoder	Host Library for decoding defmt log frames
defmt-parser	./parser	Host Library for parsing defmt log frames
defmt-rtt	./firmware/defmt-rtt	On-target library for sending defmt logs over RTT
defmt-itm	./firmware/defmt-itm	On-target library for sending defmt logs over ITM
defmt-semihosting	./firmware/defmt-semihosting	On-target library for sending defmt logs over semihosting
panic-probe	./firmware/panic-probe	On-target library for sending panic! over defmt
defmt-test	./firmware/defmt-test	Framework for running tests on-target
defmt-test-macros	./firmware/defmt-test/macros	Proc Macros for defmt-test
defmt-json-schema	./defmt/defmt-json-schema	Describes the JSON emitted by defmt-decoder

MSRV

The minimum supported Rust version is 1.76 (or Ferrocene 24.05). defmt is tested against the latest stable Rust version and the MSRV.

Developer Information

Running Tests

Tests are run using cargo xtask -- although this is simply an alias (defined in .cargo/config.toml) for cargo run --package xtask --.

To see a list of options, see xtask/src/main.rs, or run:

cargo xtask help

For example, to run all the tests, run:

cargo xtask test-all

You will need qemu-system-arm installed and in your $PATH for some of the tests (e.g. test-snapshot).

Support

defmt is part of the Knurling project, Ferrous Systems' effort at improving tooling used to develop for embedded systems.

If you think that our work is useful, consider sponsoring it via GitHub Sponsors.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

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 licensed as above, without any additional terms or conditions.