Support embedded targets

bins/esp/.cargo/config.toml

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+[target.xtensa-esp32s3-none-elf]
+runner = "probe-rs run --chip=esp32s3 --preverify --always-print-stacktrace --no-location --catch-hardfault"
+
+[env]
+
+[build]
+rustflags = [
+  "-C", "link-arg=-nostartfiles",
+]
+
+target = "xtensa-esp32s3-none-elf"
+
+[unstable]
+build-std = ["alloc", "core"]

bins/esp/.gitignore

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+# will have compiled files and executables
+debug/
+target/
+
+# Editor configuration
+.vscode/
+.zed/
+.helix/
+.nvim.lua
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+
+# RustRover
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/

bins/esp/Cargo.toml

@@ -0,0 +1,72 @@
+[package]
+edition = "2024"
+name = "picocraft-esp32s3"
+rust-version = "1.88"
+version = "0.1.0"
+
+[[bin]]
+name = "esp32s3"
+path = "./src/bin/esp32s3.rs"
+test = false
+
+[[test]]
+harness = false
+name = "hello_test"
+
+[lib]
+test = false
+
+[dependencies]
+esp-hal = { version = "1.0.0", features = ["esp32s3", "unstable"] }
+
+esp-rtos = { version = "0.2.0", features = [
+  "embassy",
+  "esp-alloc",
+  "esp-radio",
+  "esp32s3",
+] }
+
+esp-bootloader-esp-idf = { version = "0.4.0", features = ["esp32s3"] }
+
+embassy-net = { version = "0.8.0", features = [
+  "dhcpv4",
+  "medium-ethernet",
+  "tcp",
+  "udp",
+] }
+embedded-io = "0.7.1"
+embedded-io-async = "0.7.0"
+esp-alloc = "0.9.0"
+rtt-target = "0.6.2"
+# for more networking protocol support see https://crates.io/crates/edge-net
+embassy-executor = { version = "0.9.1", features = [] }
+embassy-time = "0.5.0"
+esp-radio = { version = "0.17.0", features = [
+  "esp-alloc",
+  "esp32s3",
+  "smoltcp",
+  "unstable",
+  "wifi",
+] }
+smoltcp = { version = "0.12.0", default-features = false, features = [
+  "medium-ethernet",
+  "multicast",
+  "proto-dhcpv4",
+  "proto-dns",
+  "proto-ipv4",
+  "socket-dns",
+  "socket-icmp",
+  "socket-raw",
+  "socket-tcp",
+  "socket-udp",
+] }
+
+critical-section = "1.2.0"
+static_cell = "2.1.1"
+
+[dev-dependencies]
+embedded-test = { version = "0.7.0", features = [
+  "embassy",
+  "external-executor",
+  "xtensa-semihosting",
+] }

bins/esp/build.rs

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+fn main() {
+    linker_be_nice();
+    println!("cargo:rustc-link-arg-tests=-Tembedded-test.x");
+    // make sure linkall.x is the last linker script (otherwise might cause problems
+    // with flip-link)
+    println!("cargo:rustc-link-arg=-Tlinkall.x");
+}
+
+fn linker_be_nice() {
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() > 1 {
+        let kind = &args[1];
+        let what = &args[2];
+
+        match kind.as_str() {
+            "undefined-symbol" => match what.as_str() {
+                "_defmt_timestamp" => {
+                    eprintln!();
+                    eprintln!(
+                        "💡 `defmt` not found - make sure `defmt.x` is added as a linker script \
+                         and you have included `use defmt_rtt as _;`"
+                    );
+                    eprintln!();
+                }
+                "_stack_start" => {
+                    eprintln!();
+                    eprintln!("💡 Is the linker script `linkall.x` missing?");
+                    eprintln!();
+                }
+                "esp_rtos_initialized" | "esp_rtos_yield_task" | "esp_rtos_task_create" => {
+                    eprintln!();
+                    eprintln!(
+                        "💡 `esp-radio` has no scheduler enabled. Make sure you have initialized \
+                         `esp-rtos` or provided an external scheduler."
+                    );
+                    eprintln!();
+                }
+                "embedded_test_linker_file_not_added_to_rustflags" => {
+                    eprintln!();
+                    eprintln!(
+                        "💡 `embedded-test` not found - make sure `embedded-test.x` is added as a \
+                         linker script for tests"
+                    );
+                    eprintln!();
+                }
+                _ => (),
+            },
+            // we don't have anything helpful for "missing-lib" yet
+            _ => {
+                std::process::exit(1);
+            }
+        }
+
+        std::process::exit(0);
+    }
+
+    println!(
+        "cargo:rustc-link-arg=-Wl,--error-handling-script={}",
+        std::env::current_exe().unwrap().display()
+    );
+}

bins/esp/rust-toolchain.toml

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+[toolchain]
+channel = "esp"

bins/esp/src/bin/esp32s3.rs

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+#![no_std]
+#![no_main]
+#![deny(
+    clippy::mem_forget,
+    reason = "mem::forget is generally not safe to do with esp_hal types, especially those \
+              holding buffers for the duration of a data transfer."
+)]
+
+use embassy_executor::Spawner;
+use embassy_time::{Duration, Timer};
+use esp_hal::clock::CpuClock;
+use esp_hal::timer::timg::TimerGroup;
+use rtt_target::rprintln;
+
+#[panic_handler]
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+extern crate alloc;
+
+// This creates a default app-descriptor required by the esp-idf bootloader.
+// For more information see: <https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/app_image_format.html#application-description>
+esp_bootloader_esp_idf::esp_app_desc!();
+
+#[esp_rtos::main]
+async fn main(spawner: Spawner) -> ! {
+    // generator version: 1.0.1
+
+    rtt_target::rtt_init_print!();
+
+    let config = esp_hal::Config::default().with_cpu_clock(CpuClock::max());
+    let peripherals = esp_hal::init(config);
+
+    esp_alloc::heap_allocator!(#[esp_hal::ram(reclaimed)] size: 73744);
+
+    let timg0 = TimerGroup::new(peripherals.TIMG0);
+    esp_rtos::start(timg0.timer0);
+
+    rprintln!("Embassy initialized!");
+
+    let radio_init = esp_radio::init().expect("Failed to initialize Wi-Fi/BLE controller");
+    let (mut _wifi_controller, _interfaces) =
+        esp_radio::wifi::new(&radio_init, peripherals.WIFI, Default::default())
+            .expect("Failed to initialize Wi-Fi controller");
+
+    // TODO: Spawn some tasks
+    let _ = spawner;
+
+    loop {
+        rprintln!("Hello world!");
+        Timer::after(Duration::from_secs(1)).await;
+    }
+
+    // for inspiration have a look at the examples at https://github.com/esp-rs/esp-hal/tree/esp-hal-v1.0.0/examples/src/bin
+}

bins/esp/src/lib.rs

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+#![no_std]

bins/esp/tests/hello_test.rs

@@ -0,0 +1,27 @@
+//! Demo test suite using embedded-test
+//!
+//! You can run this using `cargo test` as usual.
+
+#![no_std]
+#![no_main]
+
+esp_bootloader_esp_idf::esp_app_desc!();
+
+#[cfg(test)]
+#[embedded_test::tests(executor = esp_rtos::embassy::Executor::new())]
+mod tests {
+
+    #[init]
+    fn init() {
+        let peripherals = esp_hal::init(esp_hal::Config::default());
+
+        let timg1 = esp_hal::timer::timg::TimerGroup::new(peripherals.TIMG1);
+        esp_rtos::start(timg1.timer0);
+    }
+
+    #[test]
+    async fn hello_test() {
+        embassy_time::Timer::after(embassy_time::Duration::from_millis(100)).await;
+        assert_eq!(1 + 1, 2);
+    }
+}