samples: embassy: Start of an embassy demo

This demo shows shows a few async tasks that are coordinated using the
Embassy embassy-thread executor.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

samples/embassy/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+
+project(embassy_on_zephyr)
+rust_cargo_application()

samples/embassy/Cargo.toml

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+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+[package]
+# This must be rustapp for now.
+name = "rustapp"
+version = "0.1.0"
+edition = "2021"
+description = "A sample hello world application in Rust"
+license = "Apache-2.0 or MIT"
+
+[lib]
+crate-type = ["staticlib"]
+
+[dependencies]
+zephyr = { version = "0.1.0", features = ["time-driver"] }
+log = "0.4.22"
+static_cell = "2.1"
+
+[dependencies.embassy-executor]
+version = "0.7.0"
+# path = "../../embassy/embassy-executor"
+features = [
+  "log",
+  "task-arena-size-1024",
+  "arch-cortex-m",
+  "executor-thread",
+]
+
+[dependencies.embassy-futures]
+version = "0.1.1"
+# path = "../../embassy/embassy-futures"
+
+[dependencies.embassy-sync]
+version = "0.6.2"
+# path = "../../embassy/embassy-sync"
+
+[dependencies.embassy-time]
+version = "0.4.0"
+# path = "../../embassy/embassy-time"
+# This is board specific.
+features = ["tick-hz-10_000"]
+
+[dependencies.critical-section]
+version = "1.2"
+
+[profile.dev]
+opt-level = 1
+
+[profile.release]
+debug = true

samples/embassy/pimoroni_tiny_2040.conf

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+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+# This board doesn't have a serial console, so use RTT.
+CONFIG_UART_CONSOLE=n
+CONFIG_RTT_CONSOLE=y
+CONFIG_USE_SEGGER_RTT=y

samples/embassy/prj.conf

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+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_DEBUG=y
+
+# The default 1k stack isn't large enough for rust string formatting with logging.
+CONFIG_MAIN_STACK_SIZE=4096
+
+CONFIG_RUST=y
+
+CONFIG_RUST_ALLOC=y
+# CONFIG_LOG=y
+
+CONFIG_LOG_BACKEND_RTT=n

samples/embassy/rpi_pico.conf

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+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+# This board doesn't have a serial console, so use RTT.
+CONFIG_UART_CONSOLE=n
+CONFIG_RTT_CONSOLE=y
+CONFIG_USE_SEGGER_RTT=y

samples/embassy/sample.yaml

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+sample:
+  description: Embassy Hello
+  name: hello and basics from Embassy
+common:
+  harness: console
+  harness_config:
+    type: one_line
+    regex:
+      - "Hello world from Rust on (.*)"
+  tags: rust
+  filter: CONFIG_RUST_SUPPORTED
+  platform_allow:
+    - qemu_cortex_m0
+    - qemu_cortex_m3
+    - qemu_riscv32
+    - qemu_riscv64
+    - nrf52840dk/nrf52840
+tests:
+  sample.rust.helloworld:
+    tags: introduction

samples/embassy/src/lib.rs

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+// Copyright (c) 2024 Linaro LTD
+// SPDX-License-Identifier: Apache-2.0
+
+#![no_std]
+
+use embassy_executor::{Executor, Spawner};
+use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, channel::Channel};
+use embassy_time::{Duration, Timer};
+use log::info;
+use static_cell::StaticCell;
+
+static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
+
+#[no_mangle]
+extern "C" fn rust_main() {
+    unsafe {
+        zephyr::set_logger().unwrap();
+    }
+
+    info!("Hello world from Rust on {}", zephyr::kconfig::CONFIG_BOARD);
+
+    let executor = EXECUTOR_LOW.init(Executor::new());
+    executor.run(|spawner| {
+        spawner.spawn(sample_task(spawner)).unwrap();
+    })
+}
+
+static CHAN: Channel<CriticalSectionRawMutex, usize, 1> = Channel::new();
+
+#[embassy_executor::task]
+async fn sample_task(spawner: Spawner) {
+    info!("Started once");
+    spawner.spawn(other_task(spawner)).unwrap();
+    loop {
+        // Wait for a message.
+        let msg = CHAN.receive().await;
+        info!("main task got: {}", msg);
+    }
+}
+
+#[embassy_executor::task]
+async fn other_task(_spawner: Spawner) {
+    info!("The other task");
+    let mut count = 0;
+    loop {
+        CHAN.send(count).await;
+        count = count.wrapping_add(1);
+
+        Timer::after(Duration::from_secs(1)).await;
+    }
+}