add rgb check and example

AGENTS.md

@@ -1,5 +1,7 @@
 # AGENTS
 
+ALWAYS COMPACT YOUR CONTEXT FIRST!
+
 ## Map
 
 - Root has workspace files.
@@ -43,6 +45,7 @@
 - Short names.
 - Short comments.
 - Explain embedded idea.
+- Every Rust function we write except the main must have a short description header comment following rust best practice
 - Do not explain obvious Rust syntax.
 - No heap.
 - No dynamic dispatch unless teaching needs it.

Cargo.lock

@@ -408,6 +408,34 @@ dependencies = [
  "defmt 0.3.100",
 ]
 
+[[package]]
+name = "embassy-rgb"
+version = "0.1.0"
+dependencies = [
+ "cortex-m",
+ "cortex-m-rt",
+ "defmt 1.1.0",
+ "defmt-rtt",
+ "embassy-executor",
+ "embassy-stm32",
+ "embassy-time",
+ "panic-probe",
+]
+
+[[package]]
+name = "embassy-rgb-check"
+version = "0.1.0"
+dependencies = [
+ "cortex-m",
+ "cortex-m-rt",
+ "defmt 1.1.0",
+ "defmt-rtt",
+ "embassy-executor",
+ "embassy-stm32",
+ "embassy-time",
+ "panic-probe",
+]
+
 [[package]]
 name = "embassy-stm32"
 version = "0.6.0"

Cargo.toml

@@ -5,6 +5,8 @@ members = [
   "examples/button-input",
   "examples/embassy-blinky",
   "examples/embassy-button",
+  "examples/embassy-rgb-check",
+  "examples/embassy-rgb",
 ]
 resolver = "2"
 
@@ -22,3 +24,6 @@ embassy-time = "=0.5.1"
 nb = "=1.1.0"
 panic-probe = { version = "=1.0.0", features = ["print-defmt"] }
 stm32f1xx-hal = "=0.11.0"
+
+[profile.dev]
+opt-level = "s"

README.md

@@ -15,10 +15,10 @@ See [blue-pill.md](docs/hardware/blue-pill.md) for wiring notes.
 
 - internal LED: `PC13`
 - RGB LED:
-  - `PA5` = red
-  - `PA6` = green
-  - `PA7` = blue
-  - `PA4` = drive low for the LED return path
+  - `PA0` = GND, drive low
+  - `PA1` = red
+  - `PA2` = green
+  - `PA3` = blue
 - 5-way button board:
   - `PB12` = GND, drive low
   - `PA10` = VCC, drive high
@@ -97,6 +97,8 @@ probe-rs chip list | rg STM32F103
 - `button-input` - poll the center button on `PA8`, mirror state on the LED, log transitions
 - `embassy-blinky` - minimal async blink with Embassy
 - `embassy-button` - minimal Embassy polling loop for the center button on `PA8`
+- `embassy-rgb-check` - simple RGB on/off check on `PA1`/`PA2`/`PA3`
+- `embassy-rgb` - async RGB PWM animation on `PA1`/`PA2`/`PA3`
 
 The button examples assume the 5-way board is wired like this:
 

docs/hardware/blue-pill.md

@@ -15,10 +15,11 @@
 
 ## RGB LED
 
-- `PA5` = red
-- `PA6` = green
-- `PA7` = blue
-- `PA4` = drive low for the LED return path
+- `PA0` = GND, drive low
+- `PA1` = red
+- `PA2` = green
+- `PA3` = blue
+- The RGB fade example uses software PWM on `PA1`, `PA2`, and `PA3`
 
 ## 5-Way Button Board
 

examples/README.md

@@ -9,6 +9,8 @@ Each example is its own Cargo package.
 - `button-input` - poll the center button on `PA8`, mirror state to `PC13`, log transitions
 - `embassy-blinky` - minimal Embassy executor and async blink
 - `embassy-button` - minimal Embassy polling loop for the center button on `PA8`
+- `embassy-rgb-check` - simple RGB on/off check on `PA1`/`PA2`/`PA3`
+- `embassy-rgb` - async RGB PWM animation on `PA1`/`PA2`/`PA3`
 
 ## Build One Example
 
@@ -18,6 +20,8 @@ just build-timer
 just build-button
 just build-embassy-blinky
 just build-embassy-button
+just build-embassy-rgb
+just build-embassy-rgb-check
 ```
 
 ## Flash One Example
@@ -28,6 +32,8 @@ just flash-timer
 just flash-button
 just flash-embassy-blinky
 just flash-embassy-button
+just flash-embassy-rgb
+just flash-embassy-rgb-check
 ```
 
 ## Run With Logs
@@ -35,4 +41,6 @@ just flash-embassy-button
 ```bash
 just run-blinky
 just run-embassy-blinky
+just run-embassy-rgb
+just run-embassy-rgb-check
 ```

examples/embassy-blinky/Cargo.toml

@@ -11,6 +11,6 @@ cortex-m-rt.workspace = true
 defmt.workspace = true
 defmt-rtt.workspace = true
 embassy-executor = { workspace = true, features = ["defmt", "executor-thread", "platform-cortex-m"] }
-embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim2"] }
+embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim3"] }
 embassy-time.workspace = true
 panic-probe.workspace = true

examples/embassy-blinky/src/main.rs

@@ -2,9 +2,9 @@
 #![no_std]
 #![no_main]
 
+use cortex_m as _;
 use defmt::info;
 use defmt_rtt as _;
-use cortex_m as _;
 use embassy_executor::Spawner;
 use embassy_stm32::gpio::{Level, Output, Speed};
 use embassy_time::Timer;

examples/embassy-button/Cargo.toml

@@ -11,6 +11,6 @@ cortex-m-rt.workspace = true
 defmt.workspace = true
 defmt-rtt.workspace = true
 embassy-executor = { workspace = true, features = ["defmt", "executor-thread", "platform-cortex-m"] }
-embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim2"] }
+embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim3"] }
 embassy-time.workspace = true
 panic-probe.workspace = true

examples/embassy-button/src/main.rs

@@ -2,9 +2,9 @@
 #![no_std]
 #![no_main]
 
+use cortex_m as _;
 use defmt::info;
 use defmt_rtt as _;
-use cortex_m as _;
 use embassy_executor::Spawner;
 use embassy_stm32::gpio::{Input, Level, Output, Pull, Speed};
 use embassy_time::Timer;

examples/embassy-rgb-check/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "embassy-rgb-check"
+version = "0.1.0"
+edition = "2024"
+publish = false
+build = "build.rs"
+
+[dependencies]
+cortex-m.workspace = true
+cortex-m-rt.workspace = true
+defmt.workspace = true
+defmt-rtt.workspace = true
+embassy-executor = { workspace = true, features = ["defmt", "executor-thread", "platform-cortex-m"] }
+embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim3"] }
+embassy-time.workspace = true
+panic-probe.workspace = true

examples/embassy-rgb-check/build.rs

@@ -0,0 +1,12 @@
+// main: tell Cargo to rerun when memory.x changes and add the shared link path.
+// Input: none.
+// Output: build script side effects only.
+fn main() {
+    println!("cargo:rerun-if-changed=../../memory.x");
+    println!(
+        "cargo:rustc-link-search={}",
+        std::path::PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap())
+            .join("../..")
+            .display()
+    );
+}

examples/embassy-rgb-check/src/main.rs

@@ -0,0 +1,70 @@
+#![deny(unsafe_code)]
+#![no_std]
+#![no_main]
+
+use cortex_m as _;
+use defmt::info;
+use defmt_rtt as _;
+use embassy_executor::Spawner;
+use embassy_stm32::gpio::{Level, Output, Speed};
+use embassy_time::Timer;
+use panic_probe as _;
+
+const HOLD_MS: u64 = 1000;
+
+// main: cycle each RGB pin high and low in order so the LED wiring can be checked.
+// Input: the Embassy spawner, which this example does not use.
+// Output: never returns.
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(Default::default());
+    let _gnd = Output::new(p.PA0, Level::Low, Speed::Low);
+    let mut red = Output::new(p.PA1, Level::Low, Speed::Low);
+    let mut green = Output::new(p.PA2, Level::Low, Speed::Low);
+    let mut blue = Output::new(p.PA3, Level::Low, Speed::Low);
+    let mut led = Output::new(p.PC13, Level::High, Speed::Low);
+
+    loop {
+        info!("expected: red high, green low, blue low");
+        red.set_high();
+        green.set_low();
+        blue.set_low();
+        led.set_low();
+        Timer::after_millis(HOLD_MS).await;
+
+        info!("expected: red low, green low, blue low");
+        red.set_low();
+        green.set_low();
+        blue.set_low();
+        led.set_high();
+        Timer::after_millis(HOLD_MS).await;
+
+        info!("expected: red low, green high, blue low");
+        red.set_low();
+        green.set_high();
+        blue.set_low();
+        led.set_low();
+        Timer::after_millis(HOLD_MS).await;
+
+        info!("expected: red low, green low, blue low");
+        red.set_low();
+        green.set_low();
+        blue.set_low();
+        led.set_high();
+        Timer::after_millis(HOLD_MS).await;
+
+        info!("expected: red low, green low, blue high");
+        red.set_low();
+        green.set_low();
+        blue.set_high();
+        led.set_low();
+        Timer::after_millis(HOLD_MS).await;
+
+        info!("expected: red low, green low, blue low");
+        red.set_low();
+        green.set_low();
+        blue.set_low();
+        led.set_high();
+        Timer::after_millis(HOLD_MS).await;
+    }
+}

examples/embassy-rgb/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "embassy-rgb"
+version = "0.1.0"
+edition = "2024"
+publish = false
+build = "build.rs"
+
+[dependencies]
+cortex-m.workspace = true
+cortex-m-rt.workspace = true
+defmt.workspace = true
+defmt-rtt.workspace = true
+embassy-executor = { workspace = true, features = ["defmt", "executor-thread", "platform-cortex-m"] }
+embassy-stm32 = { workspace = true, features = ["defmt", "stm32f103c8", "time-driver-tim3"] }
+embassy-time.workspace = true
+panic-probe.workspace = true

examples/embassy-rgb/build.rs

@@ -0,0 +1,9 @@
+fn main() {
+    println!("cargo:rerun-if-changed=../../memory.x");
+    println!(
+        "cargo:rustc-link-search={}",
+        std::path::PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap())
+            .join("../..")
+            .display()
+    );
+}

examples/embassy-rgb/src/main.rs

@@ -0,0 +1,143 @@
+#![deny(unsafe_code)]
+#![no_std]
+#![no_main]
+
+use cortex_m as _;
+use defmt::info;
+use defmt_rtt as _;
+use embassy_executor::Spawner;
+use embassy_stm32::gpio::{Level, Output, Speed};
+use embassy_time::Timer;
+use panic_probe as _;
+
+const SMOOTH_STEPS: u16 = 64;
+const SMOOTH_STEP_MS: u64 = 30;
+const HARD_HOLD_MS: u64 = 1000;
+const PWM_FRAME_US: u64 = 10_000;
+const PWM_SLICES: u16 = 100;
+const PWM_SLICE_US: u64 = PWM_FRAME_US / PWM_SLICES as u64;
+
+// mix two 8-bit values across a fixed number of steps.
+fn blend(start_value: u8, end_value: u8, step: u16, steps: u16) -> u8 {
+    let start_value = u16::from(start_value);
+    let end_value = u16::from(end_value);
+    let step = step.min(steps);
+    let left = steps - step;
+    (((start_value * left) + (end_value * step)) / steps) as u8
+}
+
+// enerate one software PWM frame on the RGB GPIO pins
+async fn pwm_frame(
+    red: &mut Output<'_>,
+    green: &mut Output<'_>,
+    blue: &mut Output<'_>,
+    red_pct: u8,
+    green_pct: u8,
+    blue_pct: u8,
+) {
+    for slice in 0..PWM_SLICES {
+        if slice < u16::from(red_pct) {
+            red.set_high();
+        } else {
+            red.set_low();
+        }
+
+        if slice < u16::from(green_pct) {
+            green.set_high();
+        } else {
+            green.set_low();
+        }
+
+        if slice < u16::from(blue_pct) {
+            blue.set_high();
+        } else {
+            blue.set_low();
+        }
+
+        Timer::after_micros(PWM_SLICE_US).await;
+    }
+}
+
+// hold one RGB color for a fixed amount of time
+async fn show_color(
+    red: &mut Output<'_>,
+    green: &mut Output<'_>,
+    blue: &mut Output<'_>,
+    red_pct: u8,
+    green_pct: u8,
+    blue_pct: u8,
+    hold_ms: u64,
+) {
+    let frames = hold_ms / (PWM_FRAME_US / 1000);
+
+    for _ in 0..frames {
+        pwm_frame(red, green, blue, red_pct, green_pct, blue_pct).await;
+    }
+}
+
+// fade the RGB output through a soft color loop
+async fn smooth_cycle(red: &mut Output<'_>, green: &mut Output<'_>, blue: &mut Output<'_>) {
+    const COLORS: [(u8, u8, u8); 4] = [(100, 0, 0), (0, 100, 0), (0, 0, 100), (100, 0, 0)];
+
+    for pair in COLORS.windows(2) {
+        let (r0, g0, b0) = pair[0];
+        let (r1, g1, b1) = pair[1];
+
+        info!(
+            "fade step: {}% {}% {}% -> {}% {}% {}%",
+            r0, g0, b0, r1, g1, b1
+        );
+
+        for step in 0..=SMOOTH_STEPS {
+            show_color(
+                red,
+                green,
+                blue,
+                blend(r0, r1, step, SMOOTH_STEPS),
+                blend(g0, g1, step, SMOOTH_STEPS),
+                blend(b0, b1, step, SMOOTH_STEPS),
+                SMOOTH_STEP_MS,
+            )
+            .await;
+        }
+    }
+}
+
+// switch the RGB output through fixed hard colors.
+async fn hard_cycle(red: &mut Output<'_>, green: &mut Output<'_>, blue: &mut Output<'_>) {
+    const COLORS: [((u8, u8, u8), &str); 8] = [
+        ((100, 0, 0), "red"),
+        ((0, 100, 0), "green"),
+        ((0, 0, 100), "blue"),
+        ((100, 100, 0), "yellow"),
+        ((0, 100, 100), "cyan"),
+        ((100, 0, 100), "magenta"),
+        ((100, 100, 100), "white"),
+        ((0, 0, 0), "off"),
+    ];
+
+    for &((r, g, b), name) in &COLORS {
+        info!("hard step: {}", name);
+        show_color(red, green, blue, r, g, b, HARD_HOLD_MS).await;
+    }
+}
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(Default::default());
+    let _gnd = Output::new(p.PA0, Level::Low, Speed::Low);
+    let mut led = Output::new(p.PC13, Level::High, Speed::Low);
+    let mut red = Output::new(p.PA1, Level::Low, Speed::Low);
+    let mut green = Output::new(p.PA2, Level::Low, Speed::Low);
+    let mut blue = Output::new(p.PA3, Level::Low, Speed::Low);
+
+    loop {
+        led.toggle();
+        info!("phase: smooth");
+        smooth_cycle(&mut red, &mut green, &mut blue).await;
+
+        led.toggle();
+        info!("phase: hard");
+        hard_cycle(&mut red, &mut green, &mut blue).await;
+    }
+}

justfile

@@ -21,6 +21,12 @@ build-embassy-blinky:
 build-embassy-button:
     cargo build -p embassy-button
 
+build-embassy-rgb:
+    cargo build -p embassy-rgb
+
+build-embassy-rgb-check:
+    cargo build -p embassy-rgb-check
+
 flash-blinky:
     cargo build -p blinky-basic
     probe-rs download --chip {{chip}} target/{{target}}/debug/blinky-basic
@@ -41,6 +47,14 @@ flash-embassy-button:
     cargo build -p embassy-button
     probe-rs download --chip {{chip}} target/{{target}}/debug/embassy-button
 
+flash-embassy-rgb:
+    cargo build -p embassy-rgb
+    probe-rs download --chip {{chip}} target/{{target}}/debug/embassy-rgb
+
+flash-embassy-rgb-check:
+    cargo build -p embassy-rgb-check
+    probe-rs download --chip {{chip}} target/{{target}}/debug/embassy-rgb-check
+
 run-blinky:
     cargo build -p blinky-basic
     probe-rs run --chip {{chip}} target/{{target}}/debug/blinky-basic
@@ -61,6 +75,14 @@ run-embassy-button:
     cargo build -p embassy-button
     probe-rs run --chip {{chip}} target/{{target}}/debug/embassy-button
 
+run-embassy-rgb:
+    cargo build -p embassy-rgb
+    probe-rs run --chip {{chip}} target/{{target}}/debug/embassy-rgb
+
+run-embassy-rgb-check:
+    cargo build -p embassy-rgb-check
+    probe-rs run --chip {{chip}} target/{{target}}/debug/embassy-rgb-check
+
 fmt:
     cargo fmt --all