Embedded C on Vamsi Kiran | Firmware Engineer

FreeRTOS Task Management & Sensor Suite

Sat, 18 Apr 2026 10:00:00 +0000

🛠 Technology Stack

Languages: Embedded C (C11)
Operating System: FreeRTOS (POSIX Port)
Protocols: I2C, Hardware Interrupts (GPIO)
Tools: libgpiod, GDB, GCC, Linux terminal

The Project Overview

The objective was to design a robust, thread-safe sensor acquisition system on a Linux-based RTOS environment. This project demonstrates high-reliability multitasking where multiple sensors share a single communication bus without data corruption or timing jitter.

Technical Highlights

Kernel-Level Multitasking: Leveraged the FreeRTOS POSIX Port to manage three concurrent tasks using fixed-priority preemption, ensuring mission-critical tasks always receive CPU time.
Thread-Safe I2C Management: Implemented a Mutex Semaphore to arbitrate access to the I2C bus. This prevents data collisions between the ADXL345 Accelerometer and DS3231 RTC tasks when accessing shared hardware.
Asynchronous Event Handling: Developed a high-priority hardware listener using libgpiod to capture falling-edge interrupts on GPIO 17, triggering a system-wide graceful shutdown.
Deterministic Scheduling: Replaced standard sleep calls with vTaskDelayUntil() to ensure a consistent 10Hz sampling frequency, eliminating timing drift critical for real-time telemetry analysis.
Resource Cleanup: Engineered a custom shutdown() sequence ensuring all RTOS tasks are deleted and Linux file descriptors (I2C/GPIO) are properly closed before process termination.

Live RTOS Execution & Task Arbitration

The following terminal trace captures the live execution of the FreeRTOS tasks. It demonstrates the real-time arbitration of the I2C bus between the high-frequency accelerometer and the low-frequency real-time clock.

BSP-Backed Embedded Application

Wed, 15 Apr 2026 10:00:00 +0000

🛠 Technology Stack

Languages: Bare-Metal C (C11)
Hardware: STM32F407 (Discovery Board) - ARM Cortex-M4
Simulation: Renode (Antmicro)
Protocols: UART (USART2), SysTick Timer logic
Tools: arm-none-eabi-gcc, GDB, Renode

The Project Overview

A modular firmware application demonstrating a clean separation between hardware-specific drivers (BSP) and high-level application logic. The project focuses on non-blocking execution, architectural maintainability, and full system virtualization using the Renode framework.

Technical Highlights

Layered Architecture (BSP): All register-level operations (RCC, GPIO, UART) are encapsulated within a dedicated Board Support Package. The application layer interacts only with abstract APIs, containing zero raw register addresses.
Non-Blocking Logic: Replaced “busy-wait” loops with a SysTick-based interrupt system, allowing the CPU to process concurrent tasks (LED Heartbeat and Status Reporting) without stalling the execution thread.
UART Serial Driver: Developed a custom driver for USART2, featuring manual Baud Rate calculation for the 16 MHz HSI clock to ensure stable 115200 baud communication.
Virtual Hardware Validation: Successfully virtualized the STM32F407 hardware environment in Renode, enabling cycle-accurate firmware testing and UART output auditing without physical silicon.

Simulation & Hardware Verification

The project is validated using Renode to audit register-level interactions and verify the timing logic of the Board Support Package. By mapping the internal USART2 peripheral to a virtual analyzer, the firmware execution is audited for cycle-accurate behavior before deployment to physical silicon.