feat: Update hello world example

book/src/02_4_hello_world.md

@@ -13,7 +13,7 @@ cd intro/hello-world
 ✅ Build, flash, and monitor the project:
 
 ```console
-$ cargo run
+$ cargo run --release
 (...)
 Finished release [optimized] target(s) in 1.78s
 (...)
@@ -33,7 +33,7 @@ Commands:
     CTRL+C    Exit
 (...)
 (...)
-Hello world!
+INFO - Hello world!
 ```
 
 >🔎 If `cargo run` has been successful, you can exit with `ctrl+C`.

intro/hello-world/.cargo/config.toml

@@ -13,3 +13,6 @@ target = "riscv32imc-unknown-none-elf"
 
 [unstable]
 build-std = ["core"]
+
+[env]
+ESP_LOG="INFO"

intro/hello-world/Cargo.toml

@@ -6,11 +6,15 @@ edition = "2021"
 license = "MIT OR Apache-2.0"
 
 [dependencies]
-esp-hal = { version = "0.21.0", features = ["esp32c3"] }
-esp-backtrace = { version = "0.14.2", features = [
+esp-backtrace = { version = "0.14.1", features = [
     "esp32c3",
-    "panic-handler",
     "exception-handler",
+    "panic-handler",
     "println",
+]}
+
+esp-hal = { version = "0.21.0", features = [
+    "esp32c3",
 ] }
-esp-println = { version = "0.12.0", features = ["esp32c3"] }
+esp-println = { version = "0.12.0", features = ["esp32c3", "log"] }
+log = { version = "0.4.21" }

intro/hello-world/src/main.rs

@@ -2,14 +2,17 @@
 #![no_main]
 
 use esp_backtrace as _;
+use esp_hal::delay::Delay;
 use esp_hal::prelude::*;
-use esp_println::println;
+use log::info;
 
 #[entry]
 fn main() -> ! {
-    esp_hal::init(esp_hal::Config::default());
+    esp_println::logger::init_logger_from_env();
 
-    println!("Hello world!");
-
-    loop {}
+    let delay = Delay::new();
+    loop {
+        info!("Hello world!");
+        delay.delay(500.millis());
+    }
 }