Mini ECU v2 – STM32F446RE + FreeRTOS + Custom Bootloader

Mini ECU v2 is a fully functional virtual automotive ECU implemented on the
NUCLEO-F446RE using:

• STM32 HAL
• FreeRTOS
• Custom Bootloader (Phase 1 & 2 complete)
• CAN loopback telemetry
• UART CLI with live dashboard
• Virtual vehicle model + accelerator input
• Unified logging system
• CI workflow via GitHub Actions (ARM-GCC)

The project simulates a real ECU by processing virtual sensor values, displaying them over a CLI dashboard, and exchanging CAN messages. A custom bootloader chain-loads the main application and will later support OTA/FW-update protocols.

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📁 Repository Structure

mini-ecu-v2/
│
├── app/
│   └── mini_ecu_v2/          # FreeRTOS-based main ECU application
│
├── bootloader/
│   └── mini_ecu_boot/        # Custom STM32 bootloader (Phase 1 & 2 complete)
│
├── docs/
│   ├── bootloader-plan.md
│   ├── bootloader-usage.md
│   └── architecture.md
│
├── .github/
│   └── workflows/build.yml   # CI builds bootloader + app
│
├── CHANGELOG.md
└── README.md

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🚗 Main ECU Application Features

✅ Virtual Vehicle Model

• Speed (km/h)
• Engine RPM
• Coolant temperature
• All values computed in vehicle.c and updated via FreeRTOS task

✅ Accelerator (Throttle) Simulation

The NUCLEO board's B1 button acts as a throttle:

• Button pressed → speed increases
• Button released → speed decays
• RPM scales with speed

✅ CAN Telemetry (Loopback Mode)

The project uses CAN1 loopback:

• TX: publishes live vehicle telemetry
• RX: CAN frames queued and processed in a dedicated task
• Processed values feed the dashboard

✅ UART CLI + Live Dashboard

A terminal (115200 8N1) shows:

• A persistent dashboard printed at the top
• Below it: an interactive CLI

Example:

-------------------- MINI ECU V2 --------------------
Speed:  42 km/h    RPM: 2100    Coolant: 87 °C
------------------------------------------------------

> help

ANSI cursor control ensures the dashboard always stays pinned at the top.

✅ Logging Framework

Modules use:

LOG_INFO("Vehicle", "Speed updated to %d", speed);
LOG_WARN("CAN", "Invalid DLC: %d", dlc);
LOG_ERROR("CLI", "Unknown command: %s", cmd);

Logs are visible in both app and bootloader.

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🥾 Custom Bootloader (Phase 1 & 2 Complete)

📌 Flash Layout (STM32F446RE)

Region	Flash Address	Size
Bootloader	0x0800 0000	32 KB
Application	0x0800 8000	480 KB

📌 Boot Flow

1. Bootloader starts at reset
2. Shows UART banner
3. Reads B1 (active-low) to decide mode:

✔ Normal Mode

If B1 is pressed during reset:

[BOOT] Jumping to application...

Bootloader validates the app vector table, remaps VTOR, sets MSP, and jumps.

✔ Bootloader Mode

If B1 is not pressed:

[BOOT] B1 is pressed: staying in bootloader.
[BOOT] (Future) OTA / firmware update mode.

Bootloader stays active, LED blinks.

📌 Safety Checks

• Validates stack pointer range (0x2000 0000 – 0x2001 FFFF)
• Disables SysTick & NVIC IRQs before jumping
• Calls HAL_DeInit() + HAL_RCC_DeInit()
• Application linker offset handled via VECT_TAB_OFFSET

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🔧 Building the Projects

➤ Build using STM32CubeIDE

Just open each project:

• app/mini_ecu_v2
• bootloader/mini_ecu_boot

Press Build Project.

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➤ Build using CI (GitHub Actions)

The repo includes a clean, Linux-friendly Makefile for CI builds.

App:

cd app/mini_ecu_v2
make

Bootloader:

cd bootloader/mini_ecu_boot
make

These CI Makefiles:

• Compile all modules
• Do not link firmware (CubeIDE handles that)
• Ensure repo compiles on ARM-GCC without Windows paths

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🔥 Flashing Instructions

1️⃣ Flash bootloader

In CubeIDE → Run/Debug Configurations:

• Select bootloader project
• Flash to 0x08000000

2️⃣ Flash application

Your app linker script already places it at 0x08008000.
Flash normally using CubeIDE.

3️⃣ Reset board

• B1 pressed ➝ Bootloader mode
• B1 released ➝ Jump to app

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🧪 Continuous Integration (CI)

GitHub Actions performs:

• ARM-GCC installation
• Build of bootloader (Linux Makefile)
• Build of application (Linux Makefile)

The workflow ensures:

• Proper include paths
• No missing sources
• HAL/FreeRTOS modules compile correctly

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🛣️ Roadmap

✔ Completed

• FreeRTOS ECU application
• CAN loopback telemetry
• CLI + dashboard
• Logging framework
• Virtual vehicle model
• Bootloader (Phase 1 & 2)

🔜 Next Phases

Phase 3 — UART/CAN Firmware Update Protocol

• Erase App region
• Stream FW image in chunks
• CRC validation
• Flash programming state machine
• Update progress logs

Phase 4 — Secure Updates

• Firmware header structure
• Versioning
• Image signatures (HMAC or ECDSA)
• Revert/fallback strategy

Phase 5 — Web-UI or PC Tool

CLI tool for:

• Flashing firmware via UART
• Viewing logs
• Sending CAN commands

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📜 License

MIT

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🙌 Credits

Designed & developed by Karan Gandhi
Real-time embedded + firmware engineer.