Crate esp_println

Source
Expand description

§esp-println

Crates.io docs.rs MSRV Crates.io Matrix

A library that provides print!, println!, dbg! implementations and logging capabilities for Espressif devices.

  • Supports all Espressif ESP32 family devices.
  • Supports different communication methods:
    • UART (Default)
    • JTAG-Serial (Only available in ESP32-C3, ESP32-C6, ESP32-H2, ESP32-S3)
    • No-op: Turns printing into a no-op
  • Supports defmt backend

§Usage

esp-println = { version = "0.11.0", features = ["esp32c2"] }

or cargo add esp-println --features esp32c2 It’s important to specify your target device as feature.

Then in your program:

use esp_println::println;

You can now println!("Hello world") as usual.

§Features

  • There is one feature for each supported target: esp32, esp32c2, esp32c3, esp32c6, esp32h2, esp32s2, and esp32s3.
    • One of these features must be enabled.
    • Only one of these features can be enabled at a time.
  • There is one feature for each supported communication method: uart, jtag-serial and auto.
    • Only one of these features can be enabled at a time.
  • no-op: Don’t print anything.
  • log: Enables logging using log crate.
  • colors: Enable colored logging.
    • Only effective when using the log feature.
  • critical-section: Enables critical sections.
  • defmt-espflash: This is intended to be used with espflash, see -L/--log-format argument of flash or monitor subcommands of espflash and cargo-espflash. Uses rzCOBS encoding and adds framing.

§Default Features

By default, we use the auto, critial-section and colors features. Which means that it will auto-detect if it needs to print to the UART or JTAG-Serial, use critical sections and output messages will be colored. If we want to use a communication method that is not auto, the default one, we need to disable the default features.

§Logging

With the feature log activated you can initialize a simple logger like this

init_logger(log::LevelFilter::Info);

There is a default feature colors which enables colored log output.

Additionally, you can use

init_logger_from_env();

In this case the following environment variables are used:

  • ESP_LOG log messages you want to show, similar to RUST_LOG. RegEx is not supported. e.g. warn,test::foo=info,test::foo::bar=debug

If this simple logger implementation isn’t sufficient for your needs, you can implement your own logger on top of esp-println. See Implementing a Logger section log documentaion

§defmt

Using the defmt-espflash feature, esp-println will install a defmt global logger. The logger will output to the same data stream as println!(), and adds framing bytes so it can be used even with other, non-defmt output. Using the defmt-espflash feature automatically uses the rzCOBS encoding and does not allow changing the encoding.

Follow the defmt book’s setup instructions on how to set up defmt. Remember, the global logger is already installed for you by esp-println!

Please note that defmt does not provide MSRV guarantees with releases, and as such we are not able to make any MSRV guarantees when this feature is enabled. For more information refer to the MSRV section of defmt’s README:
https://github.com/knurling-rs/defmt?tab=readme-ov-file#msrv

§Troubleshooting linker errors

If you experience linker errors, make sure you have some reference to esp_println in your code. If you don’t use esp_println directly, you’ll need to add e.g. use esp_println as _; to your import statements. This ensures that the global logger will not be removed by the compiler.

§Minimum Supported Rust Version (MSRV)

This crate is guaranteed to compile when using the latest stable Rust version at the time of the crate’s release. It might compile with older versions, but that may change in any new release, including patches.

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

Macros§

dbg
Prints and returns the value of a given expression for quick and dirty debugging.
print
Prints to the selected output.
println
Prints to the selected output, with a newline.

Structs§

Printer
The printer that is used by the print! and println! macros.