kernel

ESP32 Kernel

A minimal kernel for the ESP32 microcontroller. Part of the computer vision project for embedded obstacle detection.

Overview

This kernel provides a basic foundation for running the CNN object detection model on ESP32 hardware. It's lightweight and efficient, good for real-time processing with limited resources.

Project structure

kernel/
├── src/                    # Source files
│   ├── boot.S             # Assembly boot code
│   ├── kernel.c           # Main kernel implementation
│   └── linker.ld          # Linker script
├── include/               # Header files
│   └── kernel.h           # Kernel interface
├── Makefile               # Build system
└── README.md              # This file

Features

• Minimal Footprint: Lightweight kernel suitable for ESP32's limited resources
• Bare Metal: Runs without an operating system for maximum performance
• Modular Design: Clean separation between boot code and kernel logic
• Extensible: Designed to be easily extended with additional functionality

Requirements

• Hardware: ESP32 development board
• Toolchain: ESP32 GCC toolchain (xtensa-esp32-elf-gcc)
• Tools: esptool.py for flashing

Building

Prerequisites

1. Install ESP32 toolchain:

   # On Ubuntu/Debian
   sudo apt-get install gcc-xtensa-esp32-elf
   
   # Or download from Espressif
   # https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/

2. Install esptool:

   pip install esptool

Build commands

# Build kernel
make all

# Clean build artifacts
make clean

# Full clean
make fclean

# Rebuild from scratch
make re

Flashing

# Flash to ESP32 (adjust port as needed)
make flash

# Manual flashing with custom port
esptool.py --chip esp32 --port /dev/ttyUSB0 write_flash 0x10000 kernel.bin

Architecture

Boot process

1. Hardware Reset: ESP32 boot ROM initializes basic hardware
2. Boot Code (boot.S): Sets up stack and calls kernel
3. Kernel Entry (kernel_main()): Main kernel initialization and loop

Current implementation

The current kernel is minimal and includes:

• Basic hardware initialization
• Stack setup
• Main kernel loop with power management
• Placeholder for future extensions

Future extensions

The kernel is designed to be extended with:

• CNN Integration: Loading and running the trained model
• Camera Interface: Reading from ESP32-CAM or similar
• Communication: WiFi/BLE for data transmission
• Real-time Processing: Optimized inference pipeline
• Power Management: Dynamic frequency scaling and sleep modes

Development

Adding new features

1. Header Files: Add function declarations to include/kernel.h
2. Implementation: Add code to src/kernel.c
3. Build: Update Makefile if new source files are added
4. Test: Build and flash to verify functionality

Debugging

• Use esptool.py to monitor serial output
• Add debug prints to kernel code
• Use ESP32's built-in debugging capabilities

Troubleshooting

Common issues

1. Build Errors: Ensure ESP32 toolchain is properly installed
2. Flash Errors: Check USB connection and port settings
3. Runtime Issues: Verify memory layout and stack setup

Getting help

• Check ESP32 documentation: https://docs.espressif.com/
• Review linker script for memory layout issues
• Verify toolchain installation and PATH settings

License

See the main project LICENSE file for details.