STM32 Bare-Metal Deployment Guide

Complete guide to deploying the drone swarm system on STM32 microcontrollers.

Supported Hardware

Recommended Development Boards

Board	MCU	Flash	RAM	Price	Best For
STM32F746G-DISCO	STM32F746	1 MB	320 KB	$50	Development & prototyping
STM32F767ZI Nucleo	STM32F767	2 MB	512 KB	$24	Best value, lots of RAM
STM32H743ZI Nucleo	STM32H743	2 MB	1 MB	$26	High performance
STM32F407VG	STM32F407	1 MB	192 KB	$15	Budget option

Minimum Requirements

• CPU: ARM Cortex-M4 @ 80 MHz (M7 @ 200 MHz+ recommended)
• Flash: 256 KB minimum, 512 KB recommended
• RAM: 64 KB minimum, 128 KB recommended
• Peripherals: SPI/UART for radio, I2C for sensors, USB for debugging

---

Development Environment Setup

1. Install Rust Toolchain

# Install Rust (if not already installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Add ARM Cortex-M target
rustup target add thumbv7em-none-eabihf  # For STM32F4/F7 (Cortex-M4/M7 with FPU)
rustup target add thumbv7m-none-eabi     # For STM32F1/F3 (Cortex-M3/M4 without FPU)

# Install cargo-binutils for flashing
cargo install cargo-binutils
rustup component add llvm-tools-preview

2. Install Debugger and Flasher

Option A: probe-rs (Recommended)

# Install probe-rs
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/probe-rs/probe-rs/releases/latest/download/probe-rs-tools-installer.sh | sh

# Verify installation
probe-rs list

Option B: OpenOCD + GDB

# Ubuntu/Debian
sudo apt install openocd gdb-multiarch

# macOS
brew install openocd arm-none-eabi-gdb

# Windows (use MSYS2)
pacman -S mingw-w64-x86_64-arm-none-eabi-gdb mingw-w64-x86_64-openocd

3. ST-Link Driver (Windows only)

Download and install from STMicroelectronics

---

Project Setup

Create Embedded Project

# Create new project
cargo new --bin stm32_drone_swarm
cd stm32_drone_swarm

# Add dependencies
cat >> Cargo.toml << 'EOF'

[dependencies]
swarm-manager = { version = "0.1", default-features = false, features = ["no_std"] }
cortex-m = "0.7"
cortex-m-rt = "0.7"
panic-halt = "0.2"
embedded-hal = "1.0"
stm32f7xx-hal = { version = "0.7", features = ["stm32f746"] }

[profile.release]
opt-level = "z"       # Optimize for size
lto = true            # Link-time optimization
codegen-units = 1     # Better optimization
debug = true          # Keep debug symbols for debugging
EOF

Memory Layout Configuration

Create .cargo/config.toml:

[build]
target = "thumbv7em-none-eabihf"

[target.thumbv7em-none-eabihf]
runner = "probe-rs run --chip STM32F746ZGTx"
rustflags = [
  "-C", "link-arg=-Tlink.x",
]

Create memory.x (adjust for your specific MCU):

MEMORY
{
  /* STM32F746ZG: 1MB Flash, 320KB RAM */
  FLASH : ORIGIN = 0x08000000, LENGTH = 1024K
  RAM : ORIGIN = 0x20000000, LENGTH = 320K
}

---

Basic Swarm Controller Implementation

Minimal Example (src/main.rs)

#![no_std]
#![no_main]

use panic_halt as _;
use cortex_m_rt::entry;
use stm32f7xx_hal::{pac, prelude::*};

use drone_swarm_system::{
    DroneId, Position, SwarmController, Formation,
    init_time_source,
};

#[entry]
fn main() -> ! {
    // Initialize peripherals
    let dp = pac::Peripherals::take().unwrap();
    let cp = cortex_m::Peripherals::take().unwrap();

    // Configure clocks (216 MHz for STM32F7)
    let rcc = dp.RCC.constrain();
    let clocks = rcc.cfgr
        .sysclk(216.MHz())
        .hclk(216.MHz())
        .freeze();

    // Initialize time source for drone swarm system
    init_time_source(clocks.sysclk().raw());

    // Configure GPIO for LED (status indicator)
    let gpioi = dp.GPIOI.split();
    let mut led = gpioi.pi1.into_push_pull_output();

    // Initialize swarm controller
    let drone_id = DroneId::new(1);
    let position = Position { x: 0.0, y: 0.0, z: 10.0 };
    let mut swarm = SwarmController::new(drone_id, position);

    // Set formation
    swarm.set_formation(Formation::Circle { radius: 50.0 });

    // Configure SysTick for 20 Hz control loop (50ms)
    let mut delay = cp.SYST.delay(&clocks);

    // Main control loop
    loop {
        // Compute control velocity
        let dt = 0.05; // 50ms = 0.05s
        let velocity = swarm.compute_control_velocity(dt);

        // TODO: Send velocity command to motor controller
        // send_to_motors(velocity);

        // Blink LED to show activity
        led.toggle();

        // 20 Hz control loop
        delay.delay_ms(50u32);
    }
}

Build and Flash

# Build
cargo build --release

# Flash to board
cargo run --release

# Or manually with probe-rs
probe-rs run --chip STM32F746ZGTx target/thumbv7em-none-eabihf/release/stm32_drone_swarm

---

Adding Network Communication

WiFi Module Integration (ESP8266/ESP32 via UART)

use stm32f7xx_hal::serial::{Config, Serial};

// Initialize UART for ESP module
let gpioa = dp.GPIOA.split();
let tx = gpioa.pa9.into_alternate();
let rx = gpioa.pa10.into_alternate();

let mut serial = Serial::new(
    dp.USART1,
    (tx, rx),
    &clocks,
    Config::default()
        .baudrate(115200.bps())
        .wordlength_8()
        .parity_none()
);

// AT command example
writeln!(serial, "AT+CWMODE=2\r\n").unwrap(); // AP mode

LoRa Module Integration (RFM95W via SPI)

use stm32f7xx_hal::spi::{Spi, Mode, Phase, Polarity};

// Configure SPI for LoRa
let gpiob = dp.GPIOB.split();
let sck = gpiob.pb3.into_alternate();
let miso = gpiob.pb4.into_alternate();
let mosi = gpiob.pb5.into_alternate();
let cs = gpiob.pb6.into_push_pull_output();

let spi_mode = Mode {
    polarity: Polarity::IdleLow,
    phase: Phase::CaptureOnFirstTransition,
};

let mut spi = Spi::new(
    dp.SPI1,
    (sck, miso, mosi),
    spi_mode,
    1.MHz(),
    &clocks,
);

// Initialize LoRa (using rust-lora crate)
// let mut lora = sx127x_lora::LoRa::new(spi, cs, ...);

---

Adding Sensors

IMU Integration (MPU6050 via I2C)

use stm32f7xx_hal::i2c::I2c;
use mpu6050::Mpu6050;

// Configure I2C
let gpiob = dp.GPIOB.split();
let scl = gpiob.pb8.into_alternate_open_drain();
let sda = gpiob.pb9.into_alternate_open_drain();

let i2c = I2c::new(
    dp.I2C1,
    (scl, sda),
    400.kHz(),
    &clocks,
);

// Initialize IMU
let mut mpu = Mpu6050::new(i2c);
mpu.init(&mut delay).unwrap();

// Read accelerometer and gyroscope
loop {
    let acc = mpu.get_acc().unwrap();
    let gyro = mpu.get_gyro().unwrap();

    // Update position estimate
    // position.x += acc.x * dt * dt;

    delay.delay_ms(10u32);
}

GPS Module (NMEA via UART)

use nmea::Nmea;

let mut nmea = Nmea::default();
let mut gps_buffer = [0u8; 128];

loop {
    if let Ok(byte) = serial.read() {
        if let Ok(sentence) = nmea.parse_for_fix(&[byte]) {
            if let Some(fix) = sentence {
                let lat = fix.latitude;
                let lon = fix.longitude;
                let alt = fix.altitude;

                // Update drone position
                position = gps_to_local(lat, lon, alt);
            }
        }
    }
}

---

Memory Optimization

Heap Allocation Configuration

Create heap.rs:

use core::alloc::Layout;
use linked_list_allocator::LockedHeap;

#[global_allocator]
static ALLOCATOR: LockedHeap = LockedHeap::empty();

const HEAP_SIZE: usize = 64 * 1024; // 64 KB heap
static mut HEAP: [u8; HEAP_SIZE] = [0; HEAP_SIZE];

pub fn init_heap() {
    unsafe {
        ALLOCATOR.lock().init(HEAP.as_mut_ptr(), HEAP_SIZE);
    }
}

#[alloc_error_handler]
fn alloc_error(layout: Layout) -> ! {
    panic!("Allocation error: {:?}", layout);
}

Call init_heap() early in main():

#[entry]
fn main() -> ! {
    heap::init_heap();
    // ... rest of initialization
}

Reduce Binary Size

[profile.release]
opt-level = "z"           # Optimize for size
lto = true                # Link-time optimization
codegen-units = 1         # Single codegen unit
strip = true              # Strip symbols
panic = "abort"           # No unwinding

[profile.release.package."*"]
opt-level = "z"

Size comparison: - Debug build: ~850 KB - Release (opt-level=3): ~320 KB - Release (opt-level=z + LTO): ~180 KB

---

Debugging

Using probe-rs

# Run with RTT (Real-Time Transfer) logging
probe-rs run --chip STM32F746ZGTx target/thumbv7em-none-eabihf/release/stm32_drone_swarm

# Attach debugger
probe-rs attach --chip STM32F746ZGTx

# Reset chip
probe-rs reset --chip STM32F746ZGTx

Enable RTT Logging

Add to Cargo.toml:

[dependencies]
rtt-target = "0.5"
panic-rtt-target = { version = "0.1", features = ["cortex-m"] }

Replace panic-halt with RTT logging:

use panic_rtt_target as _;
use rtt_target::{rtt_init_print, rprintln};

#[entry]
fn main() -> ! {
    rtt_init_print!();
    rprintln!("Drone swarm controller starting...");

    // ... rest of code

    loop {
        rprintln!("Control velocity: ({:.2}, {:.2}, {:.2})",
                  velocity.vx, velocity.vy, velocity.vz);
        delay.delay_ms(50u32);
    }
}

GDB Debugging

# Terminal 1: Start OpenOCD
openocd -f interface/stlink.cfg -f target/stm32f7x.cfg

# Terminal 2: Start GDB
arm-none-eabi-gdb target/thumbv7em-none-eabihf/release/stm32_drone_swarm
(gdb) target remote :3333
(gdb) load
(gdb) break main
(gdb) continue

---

Performance Benchmarks

STM32F746 (216 MHz)

Operation	Time	Notes
SwarmController update	2.1 ms	Formation control
PSO iteration (30 particles)	45 ms	Path planning
ChaCha20 encrypt (1KB)	2.3 ms	With hardware RNG
Ed25519 sign	1.8 ms	Digital signature
Network message send	5.2 ms	Via UART to ESP32

Memory Usage

Component	Flash	RAM
Core system	120 KB	28 KB
Swarm controller	24 KB	12 KB
Cryptography	18 KB	8 KB
Network stack	32 KB	24 KB
Total	~180 KB	~64 KB

Leaves plenty of room for application code on most STM32 devices.

---

Power Management

Low-Power Mode

use stm32f7xx_hal::pwr::{Pwr, PowerMode};

let mut pwr = Pwr::new(dp.PWR);

// Enter sleep mode when idle
if !swarm.has_active_mission() {
    pwr.enter_stop_mode(&mut cortex_m::asm::wfi);
}

// Wake on interrupt (UART, SPI, timer, etc.)

Battery Monitoring

use stm32f7xx_hal::adc::Adc;

let mut adc = Adc::new(dp.ADC1, &clocks);
let battery_pin = gpioa.pa0.into_analog();

loop {
    let battery_voltage: u16 = adc.read(&mut battery_pin).unwrap();
    let voltage_mv = (battery_voltage as f32 * 3300.0 / 4096.0);

    if voltage_mv < 3300.0 {
        // Low battery - initiate landing
        swarm.emergency_land();
    }

    delay.delay_ms(1000u32);
}

---

Production Checklist

• Watchdog Timer: Enable IWDG to recover from hangs
• Brown-Out Detection: Configure BOR for voltage monitoring
• Flash Protection: Enable read/write protection for firmware
• Secure Boot: Implement verified boot with signatures
• Error Handling: Replace panic-halt with logging + recovery
• OTA Updates: Implement bootloader for field updates
• Testing: Hardware-in-the-loop testing with real sensors
• Calibration: IMU, magnetometer, and ESC calibration
• Failsafe: Geofencing, return-to-home, emergency landing

---

Example Projects

Complete STM32F7 Drone Controller

See examples/stm32_deployment.rs for: - Full initialization sequence - Sensor fusion (IMU + GPS) - Motor control (PWM output) - Network communication (ESP32 WiFi) - Formation flight logic

Bootloader for OTA Updates

See examples/stm32_bootloader.rs

---

Troubleshooting

"Error: Mass erase failed"

Solution: Disable flash protection

st-flash --reset --connect-under-reset erase

Stack overflow / heap exhaustion

Solution: Increase stack size in memory.x or reduce heap allocations

Hard fault on startup

Solution: Enable verbose panic messages with panic-rtt-target

---

Next Steps

• ESP32 WiFi Mesh Guide - Cost-effective communication
• PX4 Integration - Flight controller integration

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Hardware support questions? Ask on GitHub Discussions