Executive Summary

The fourth quarter of 2024 marked a complete transformation of the widget controller firmware, evolving from a bare-metal implementation to a production-ready RTOS-based platform. This modernization effort has established a solid foundation for future product development while significantly improving system reliability, power efficiency, and maintainability. The firmware is now ready for initial production runs with full OTA update capability and comprehensive manufacturing support.

Key Achievements & Features

1. RTOS Migration: Successfully transitioned from a monolithic super-loop architecture to FreeRTOS, enabling preemptive multitasking and improving system responsiveness under load.
2. Sensor Fusion System: Implemented a unified environmental monitoring system with Kalman filtering, supporting temperature, humidity, and pressure sensing with automatic calibration.
3. Over-the-Air Updates: Developed a dual-bank firmware architecture with cryptographic signature verification, enabling secure field updates with automatic rollback on failure.
4. Automated Testing: Established a comprehensive hardware-in-the-loop testing framework with CI/CD integration, ensuring regression-free releases.
5. Manufacturing Readiness: Created dedicated manufacturing test modes, device provisioning workflows, and QR code-based labeling systems.

Technology & Language Trends

The project demonstrates modern embedded development practices:

• Firmware: Adopted FreeRTOS for task management, with careful attention to priority design and resource synchronization.
• Security: Implemented Ed25519 signature verification for firmware authentication, establishing a proper chain of trust.
• Testing: Python-based test automation with pytest enables rapid iteration and confident releases.
• Documentation: Comprehensive API documentation and integration guides ensure smooth partner onboarding.

Project Focus Areas

• Q4 Foundation Work: The quarter focused on establishing the architectural foundation—RTOS migration, HAL development, and communication stack improvements.
• Reliability Engineering: Significant effort went into power management, error handling, and recovery mechanisms.
• Production Preparation: Final month dedicated to OTA support, manufacturing workflows, and documentation.

Development Highlights

• Three-Tier Power Management: Active, Idle, and Deep Sleep modes with intelligent automatic transitions based on system activity.
• Hardware Abstraction: Clean HAL layer enables future porting to different microcontroller families with minimal code changes.
• Atomic Configuration: Shadow-write-and-commit pattern prevents configuration corruption during power loss.

Suggested Blog Posts

1. From Bare Metal to RTOS: A Migration Story
   • Lessons learned transitioning a production firmware to FreeRTOS, including task design patterns and common pitfalls.
2. Secure OTA Updates for Resource-Constrained Devices
   • How to implement cryptographically secure firmware updates with rollback support on microcontrollers.
3. Building a Hardware-in-the-Loop Test Framework
   • Using Python and pytest to create reproducible hardware tests with mock sensor injection.