Target side implementation of the RTT (Real-Time Transfer) I/O protocol. RTT implements input and output via a debug probe using in-memory ring buffers and polling. This enables debug logging from the microcontroller with minimal delays and no blocking, making it usable even in real-time applications where e.g. semihosting delays cannot be tolerated.

A platform-specific critical-section implementation is needed to use this library.

Output directly to a channel object with write! or the binary write method does not require locking and therefore does not need any platform-specific critical section.

With a platform-specific critical section in use, printing is as simple as:

use rtt_target::{rtt_init_print, rprintln};

fn main() {
    rtt_init_print!();
    loop {
        rprintln!("Hello, world!");
    }
}

rtt-target also supports initializing multiple RTT channels, and even has a logger implementations for log and defmt that can be used in conjunction with arbitrary channel setups.

The defmt integration requires setting features = ["defmt"]. Furthermore, you have to either invoke rtt_init_defmt! or set up your channel(s) manually and invoke set_defmt_channel before using defmt.

The log integration requires setting features = ["log"]. Furthermore, you have to either invoke rtt_init_log! or set up your channel(s) manually and invoke init_logger/init_logger_with_level before using log.

Note: For your platform, particularly if you're using a multi-core MCU, external logger implementations might be better suited than the one provided by this crate via the log/defmt feature.

For more information, please check out the documentation.

The examples-cortex-m and panic-test crates come with build files for the venerable STM32F103C8xx by default, but can be easily adapted for any chip as they contain only minimal platform-specific runtime code to get fn main to run.