4 files changed, 412 insertions, 20 deletions

diff --git a/examples/stm32h755cm4/Cargo.toml b/examples/stm32h755cm4/Cargo.toml
index eaaeb1ac0..cf324d3df 100644
--- a/examples/stm32h755cm4/Cargo.toml
+++ b/examples/stm32h755cm4/Cargo.toml
@@ -36,13 +36,6 @@ chrono = { version = "^0.4", default-features = false }
 grounded = "0.2.0"
 
 # cargo build/run
-[profile.dev]
-codegen-units = 1
-debug = 2
-debug-assertions = true # <-
-incremental = false
-opt-level = 3 # <-
-overflow-checks = true # <-
 
 # cargo test
 [profile.test]
@@ -55,11 +48,10 @@ overflow-checks = true # <-
 
 # cargo build/run --release
 [profile.release]
-codegen-units = 1
+codegen-units = 16
 debug = 2
 debug-assertions = false # <-
 incremental = false
-lto = 'fat'
 opt-level = 3 # <-
 overflow-checks = false # <-
 
diff --git a/examples/stm32h755cm4/src/bin/intercore.rs b/examples/stm32h755cm4/src/bin/intercore.rs
new file mode 100644
index 000000000..d5e3e7648
--- /dev/null
+++ b/examples/stm32h755cm4/src/bin/intercore.rs
@@ -0,0 +1,182 @@
+#![no_std]
+#![no_main]
+
+//! STM32H7 Secondary Core (CM4) Intercore Communication Example
+//!
+//! This example demonstrates reliable communication between the Cortex-M7 and
+//! Cortex-M4 cores. This secondary core monitors shared memory for LED state
+//! changes and updates the physical LEDs accordingly.
+//!
+//! The CM4 core handles:
+//! - Responding to state changes from CM7
+//! - Controlling the physical green and yellow LEDs
+//! - Providing visual feedback via a heartbeat on the red LED
+//!
+//! Usage:
+//! 1. Flash this CM4 (secondary) core binary first
+//! 2. Then flash the CM7 (primary) core binary
+//! 3. The red LED should blink continuously as a heartbeat
+//! 4. Green and yellow LEDs should toggle according to CM7 core signals
+
+/// Module providing shared memory constructs for intercore communication
+mod shared {
+    use core::sync::atomic::{AtomicU32, Ordering};
+
+    /// State shared between CM7 and CM4 cores for LED control
+    #[repr(C, align(4))]
+    pub struct SharedLedState {
+        pub magic: AtomicU32,
+        pub counter: AtomicU32,
+        pub led_states: AtomicU32,
+    }
+
+    // Bit positions in led_states
+    pub const GREEN_LED_BIT: u32 = 0;
+    pub const YELLOW_LED_BIT: u32 = 1;
+
+    impl SharedLedState {
+        pub const fn new() -> Self {
+            Self {
+                magic: AtomicU32::new(0xDEADBEEF),
+                counter: AtomicU32::new(0),
+                led_states: AtomicU32::new(0),
+            }
+        }
+
+        /// Set LED state by manipulating the appropriate bit in the led_states field
+        #[inline(never)]
+        #[allow(dead_code)]
+        pub fn set_led(&self, is_green: bool, state: bool) {
+            let bit = if is_green { GREEN_LED_BIT } else { YELLOW_LED_BIT };
+            let current = self.led_states.load(Ordering::SeqCst);
+
+            let new_value = if state {
+                current | (1 << bit) // Set bit
+            } else {
+                current & !(1 << bit) // Clear bit
+            };
+            self.led_states.store(new_value, Ordering::SeqCst);
+        }
+
+        /// Get current LED state
+        #[inline(never)]
+        pub fn get_led(&self, is_green: bool) -> bool {
+            let bit = if is_green { GREEN_LED_BIT } else { YELLOW_LED_BIT };
+
+            let value = self.led_states.load(Ordering::SeqCst);
+            (value & (1 << bit)) != 0
+        }
+
+        /// Increment counter and return new value
+        #[inline(never)]
+        #[allow(dead_code)]
+        pub fn increment_counter(&self) -> u32 {
+            let current = self.counter.load(Ordering::SeqCst);
+            let new_value = current.wrapping_add(1);
+            self.counter.store(new_value, Ordering::SeqCst);
+            new_value
+        }
+
+        /// Get current counter value
+        #[inline(never)]
+        pub fn get_counter(&self) -> u32 {
+            let value = self.counter.load(Ordering::SeqCst);
+            value
+        }
+    }
+
+    #[link_section = ".ram_d3"]
+    pub static SHARED_LED_STATE: SharedLedState = SharedLedState::new();
+}
+
+use core::mem::MaybeUninit;
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::gpio::{Level, Output, Speed};
+use embassy_stm32::SharedData;
+use embassy_time::Timer;
+use shared::SHARED_LED_STATE;
+use {defmt_rtt as _, panic_probe as _};
+
+#[link_section = ".ram_d3"]
+static SHARED_DATA: MaybeUninit<SharedData> = MaybeUninit::uninit();
+
+/// Task that continuously blinks the red LED as a heartbeat indicator
+#[embassy_executor::task]
+async fn blink_heartbeat(mut led: Output<'static>) {
+    loop {
+        led.toggle();
+        info!("CM4 heartbeat");
+        Timer::after_millis(500).await;
+    }
+}
+
+#[embassy_executor::main]
+async fn main(spawner: Spawner) -> ! {
+    // Initialize the secondary core
+    let p = embassy_stm32::init_secondary(&SHARED_DATA);
+    info!("CM4 core initialized!");
+
+    // Verify shared memory is accessible
+    let magic = SHARED_LED_STATE.magic.load(core::sync::atomic::Ordering::SeqCst);
+    info!("CM4: Magic value = 0x{:X}", magic);
+
+    // Set up LEDs
+    let mut green_led = Output::new(p.PB0, Level::Low, Speed::Low); // LD1
+    let mut yellow_led = Output::new(p.PE1, Level::Low, Speed::Low); // LD2
+    let red_led = Output::new(p.PB14, Level::Low, Speed::Low); // LD3 (heartbeat)
+
+    // Start heartbeat task
+    unwrap!(spawner.spawn(blink_heartbeat(red_led)));
+
+    // Track previous values to detect changes
+    let mut prev_green = false;
+    let mut prev_yellow = false;
+    let mut prev_counter = 0;
+
+    info!("CM4: Starting main loop");
+    loop {
+        // Read current values from shared memory
+        let green_state = SHARED_LED_STATE.get_led(true);
+        let yellow_state = SHARED_LED_STATE.get_led(false);
+        let counter = SHARED_LED_STATE.get_counter();
+
+        // Detect changes
+        let green_changed = green_state != prev_green;
+        let yellow_changed = yellow_state != prev_yellow;
+        let counter_changed = counter != prev_counter;
+
+        // Update LEDs and logs when values change
+        if green_changed || yellow_changed || counter_changed {
+            if counter_changed {
+                info!("CM4: Counter = {}", counter);
+                prev_counter = counter;
+            }
+
+            if green_changed {
+                if green_state {
+                    green_led.set_high();
+                    info!("CM4: Green LED ON");
+                } else {
+                    green_led.set_low();
+                    info!("CM4: Green LED OFF");
+                }
+                prev_green = green_state;
+            }
+
+            if yellow_changed {
+                if yellow_state {
+                    yellow_led.set_high();
+                    info!("CM4: Yellow LED ON");
+                } else {
+                    yellow_led.set_low();
+                    info!("CM4: Yellow LED OFF");
+                }
+                prev_yellow = yellow_state;
+            }
+        }
+
+        Timer::after_millis(10).await;
+    }
+}
diff --git a/examples/stm32h755cm7/Cargo.toml b/examples/stm32h755cm7/Cargo.toml
index e7fc05948..ac1429f30 100644
--- a/examples/stm32h755cm7/Cargo.toml
+++ b/examples/stm32h755cm7/Cargo.toml
@@ -35,15 +35,6 @@ static_cell = "2"
 chrono = { version = "^0.4", default-features = false }
 grounded = "0.2.0"
 
-# cargo build/run
-[profile.dev]
-codegen-units = 1
-debug = 2
-debug-assertions = true # <-
-incremental = false
-opt-level = 3 # <-
-overflow-checks = true # <-
-
 # cargo test
 [profile.test]
 codegen-units = 1
@@ -55,11 +46,10 @@ overflow-checks = true # <-
 
 # cargo build/run --release
 [profile.release]
-codegen-units = 1
+codegen-units = 16
 debug = 2
 debug-assertions = false # <-
 incremental = false
-lto = 'fat'
 opt-level = 3 # <-
 overflow-checks = false # <-
 
diff --git a/examples/stm32h755cm7/src/bin/intercore.rs b/examples/stm32h755cm7/src/bin/intercore.rs
new file mode 100644
index 000000000..a4e1b5ff4
--- /dev/null
+++ b/examples/stm32h755cm7/src/bin/intercore.rs
@@ -0,0 +1,228 @@
+#![no_std]
+#![no_main]
+
+//! STM32H7 Primary Core (CM7) Intercore Communication Example
+//!
+//! This example demonstrates reliable communication between the Cortex-M7 and
+//! Cortex-M4 cores using a shared memory region configured as non-cacheable
+//! via MPU settings.
+//!
+//! The CM7 core handles:
+//! - MPU configuration to make shared memory non-cacheable
+//! - Clock initialization
+//! - Toggling LED states in shared memory
+//!
+//! Usage:
+//! 1. Flash the CM4 (secondary) core binary first
+//! 2. Then flash this CM7 (primary) core binary
+//! 3. The system will start with CM7 toggling LED states and CM4 responding by
+//!    physically toggling the LEDs
+
+use core::mem::MaybeUninit;
+
+use cortex_m::asm;
+use cortex_m::peripheral::MPU;
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::{Config, SharedData};
+use embassy_time::Timer;
+use shared::{SHARED_LED_STATE, SRAM4_BASE_ADDRESS, SRAM4_REGION_NUMBER, SRAM4_SIZE_LOG2};
+use {defmt_rtt as _, panic_probe as _};
+
+/// Module providing shared memory constructs for intercore communication
+mod shared {
+    use core::sync::atomic::{AtomicU32, Ordering};
+
+    /// State shared between CM7 and CM4 cores for LED control
+    #[repr(C, align(4))]
+    pub struct SharedLedState {
+        pub magic: AtomicU32,
+        pub counter: AtomicU32,
+        pub led_states: AtomicU32,
+    }
+
+    // Bit positions in led_states
+    pub const GREEN_LED_BIT: u32 = 0;
+    pub const YELLOW_LED_BIT: u32 = 1;
+
+    impl SharedLedState {
+        pub const fn new() -> Self {
+            Self {
+                magic: AtomicU32::new(0xDEADBEEF),
+                counter: AtomicU32::new(0),
+                led_states: AtomicU32::new(0),
+            }
+        }
+
+        /// Set LED state by manipulating the appropriate bit in the led_states field
+        #[inline(never)]
+        pub fn set_led(&self, is_green: bool, state: bool) {
+            let bit = if is_green { GREEN_LED_BIT } else { YELLOW_LED_BIT };
+            let current = self.led_states.load(Ordering::SeqCst);
+
+            let new_value = if state {
+                current | (1 << bit) // Set bit
+            } else {
+                current & !(1 << bit) // Clear bit
+            };
+
+            self.led_states.store(new_value, Ordering::SeqCst);
+        }
+
+        /// Get current LED state
+        #[inline(never)]
+        #[allow(dead_code)]
+        pub fn get_led(&self, is_green: bool) -> bool {
+            let bit = if is_green { GREEN_LED_BIT } else { YELLOW_LED_BIT };
+
+            let value = self.led_states.load(Ordering::SeqCst);
+            (value & (1 << bit)) != 0
+        }
+
+        /// Increment counter and return new value
+        #[inline(never)]
+        pub fn increment_counter(&self) -> u32 {
+            let current = self.counter.load(Ordering::SeqCst);
+            let new_value = current.wrapping_add(1);
+            self.counter.store(new_value, Ordering::SeqCst);
+            new_value
+        }
+
+        /// Get current counter value
+        #[inline(never)]
+        #[allow(dead_code)]
+        pub fn get_counter(&self) -> u32 {
+            let value = self.counter.load(Ordering::SeqCst);
+            value
+        }
+    }
+
+    #[link_section = ".ram_d3"]
+    pub static SHARED_LED_STATE: SharedLedState = SharedLedState::new();
+
+    // Memory region constants for MPU configuration
+    pub const SRAM4_BASE_ADDRESS: u32 = 0x38000000;
+    pub const SRAM4_SIZE_LOG2: u32 = 15; // 64KB = 2^(15+1)
+    pub const SRAM4_REGION_NUMBER: u8 = 0;
+}
+
+#[link_section = ".ram_d3"]
+static SHARED_DATA: MaybeUninit<SharedData> = MaybeUninit::uninit();
+
+/// Configure MPU to make SRAM4 region non-cacheable
+fn configure_mpu_non_cacheable(mpu: &mut MPU) {
+    asm::dmb();
+    unsafe {
+        // Disable MPU
+        mpu.ctrl.write(0);
+
+        // Configure SRAM4 as non-cacheable
+        mpu.rnr.write(SRAM4_REGION_NUMBER as u32);
+
+        // Set base address with region number
+        mpu.rbar.write(SRAM4_BASE_ADDRESS | (1 << 4));
+
+        // Configure region attributes
+        let rasr_value: u32 = (SRAM4_SIZE_LOG2 << 1) | // SIZE=15 (64KB)
+            (1 << 0) |                                // ENABLE=1
+            (3 << 24) |                               // AP=3 (Full access)
+            (1 << 19) |                               // TEX=1
+            (1 << 18); // S=1 (Shareable)
+
+        mpu.rasr.write(rasr_value);
+
+        // Enable MPU with default memory map as background
+        mpu.ctrl.write(1 | (1 << 2)); // MPU_ENABLE | PRIVDEFENA
+    }
+
+    asm::dsb();
+    asm::isb();
+
+    info!("MPU configured - SRAM4 set as non-cacheable");
+}
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) -> ! {
+    // Set up MPU and cache configuration
+    {
+        let mut cp = cortex_m::Peripherals::take().unwrap();
+        let scb = &mut cp.SCB;
+
+        // First disable caches
+        scb.disable_icache();
+        scb.disable_dcache(&mut cp.CPUID);
+
+        // Configure MPU
+        configure_mpu_non_cacheable(&mut cp.MPU);
+
+        // Re-enable caches
+        scb.enable_icache();
+        scb.enable_dcache(&mut cp.CPUID);
+        asm::dsb();
+        asm::isb();
+    }
+
+    // Configure the clock system
+    let mut config = Config::default();
+    {
+        use embassy_stm32::rcc::*;
+        config.rcc.hsi = Some(HSIPrescaler::DIV1);
+        config.rcc.csi = true;
+        config.rcc.hsi48 = Some(Default::default());
+        config.rcc.pll1 = Some(Pll {
+            source: PllSource::HSI,
+            prediv: PllPreDiv::DIV4,
+            mul: PllMul::MUL50,
+            divp: Some(PllDiv::DIV2),
+            divq: Some(PllDiv::DIV8),
+            divr: None,
+        });
+        config.rcc.sys = Sysclk::PLL1_P;
+        config.rcc.ahb_pre = AHBPrescaler::DIV2;
+        config.rcc.apb1_pre = APBPrescaler::DIV2;
+        config.rcc.apb2_pre = APBPrescaler::DIV2;
+        config.rcc.apb3_pre = APBPrescaler::DIV2;
+        config.rcc.apb4_pre = APBPrescaler::DIV2;
+        config.rcc.voltage_scale = VoltageScale::Scale1;
+        config.rcc.supply_config = SupplyConfig::DirectSMPS;
+    }
+
+    // Initialize the CM7 core
+    let _p = embassy_stm32::init_primary(config, &SHARED_DATA);
+    info!("CM7 core initialized with non-cacheable SRAM4!");
+
+    // Verify shared memory is accessible
+    let magic = SHARED_LED_STATE.magic.load(core::sync::atomic::Ordering::SeqCst);
+    info!("CM7: Magic value = 0x{:X}", magic);
+
+    // Initialize LED states
+    SHARED_LED_STATE.set_led(true, false); // Green LED off
+    SHARED_LED_STATE.set_led(false, false); // Yellow LED off
+
+    // Main loop - periodically toggle LED states
+    let mut green_state = false;
+    let mut yellow_state = false;
+    let mut loop_count = 0;
+
+    info!("CM7: Starting main loop");
+    loop {
+        loop_count += 1;
+        let counter = SHARED_LED_STATE.increment_counter();
+
+        // Toggle green LED every second
+        if loop_count % 10 == 0 {
+            green_state = !green_state;
+            SHARED_LED_STATE.set_led(true, green_state);
+            info!("CM7: Counter = {}, Set green LED to {}", counter, green_state);
+        }
+
+        // Toggle yellow LED every 3 seconds
+        if loop_count % 30 == 0 {
+            yellow_state = !yellow_state;
+            SHARED_LED_STATE.set_led(false, yellow_state);
+            info!("CM7: Counter = {}, Set yellow LED to {}", counter, yellow_state);
+        }
+
+        Timer::after_millis(100).await;
+    }
+}