Logging - Part 1

What happens if we use the boilerplate, and no logging dependency?

In the src/main.rs we start with:

#![no_std]
#![no_main]
// None of these: esp_backtrace, esp_println, defmt
use esp_hal::{
    main,
    Config,
};
esp_bootloader_esp_idf::esp_app_desc!();

#[main]
fn main() -> ! {
    esp_hal::init(Config::default());
    panic!("Welcome.")
}

Running cargo run --release, we get:

error: #[panic_handler] function required, but not found

The panic handler is something we can define, or use a crate. For simplicity, let's use esp-backtrace with that feature, adding to Cargo.toml the following dependency:

esp-backtrace = { version = "0.18.1", features = [
    "esp32c6",
    "panic-handler",
 ]}

And to src/main.rs:

// ...
use esp_backtrace as _;
// ...

Re-run cargo run --release, and we get a new error:

error: failed to run custom build command for esp-backtrace v0.18.1 ... Exactly one of the following features must be enabled: defmt, println

So we add one:

esp-backtrace = { version = "0.18.1", features = [
    "esp32c6",
    "panic-handler",
+   "println"
]}

And yet, it errors:

error: failed to run custom build command for esp-println v0.16.1

Exactly one of the following features must be enabled: jtag-serial, uart, auto, no-op

This, it seems, would require that we add esp-println, and enable some of those features.

Since auto is a default feature, we can add:

esp-println = { version = "0.16.1", features = [
    "esp32c6",
] }

Now, it will run and panic. Yay!

Playing with these dependencies helps get a sense of what they are for. Also, to see how useful the compiler error messages can be.

Print something

So far we've not printed anything, but given esp-println is already there, we only need to use it. Then we can println!("Something") and it should work.

At this step, the code looks like:

#![no_std]
#![no_main]
use esp_hal::{
    main,
    Config,
};
use esp_backtrace as _;
use esp_println::println;
esp_bootloader_esp_idf::esp_app_desc!();

#[main]
fn main() -> ! {
    esp_hal::init(Config::default());
    println!("println!");
    panic!("Welcome.")
}

Using the log crate

We add a few items:

use esp_backtrace as _;
+use esp_println::{logger,println};
+use log::info;
esp_bootloader_esp_idf::esp_app_desc!();

And within main:

fn main() -> ! {
    esp_hal::init(Config::default());
    +logger::init_logger_from_env();
    +info!("SOME INFO!");
    println!("println!");

Finally, on Cargo.toml:

esp-println = { version = "0.16.1", features = [
"esp32c6",
+"log-04"
] }
# Manuallu, or use `cargo add log`
+log = "0.4.29"

So now we have learnt how to add a logger, if we need to.

Note

examples/logging_0.rs contains a solution. You can run it with the following command: cargo run --example logging_0 --release. You will need to have the settings above done correctly though!

In the next logging section, we analyse using defmt instead.