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Embedded Systems

Smart Sensor–Actuator Control System

A deterministic real-time sensing-to-actuation loop on STM32F4, driven entirely by timers and interrupts.

Difficulty — intermediate Complexity — 6/10 Category — Embedded Systems
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Overview

A real-time embedded control loop on the STM32F4 Discovery board designed around one hard requirement: deterministic response across the sensor's and actuator's full operating range, achieved through interrupt-driven event handling rather than polling loops.

Architecture

Peripheral drivers (GPIO/ADC/UART/I2C as required) feed a timer-scheduled, interrupt-driven control loop that continuously monitors sensor state and adjusts actuator output.

Key Features

  • Low-level peripheral drivers built for the specific sensor/actuator hardware interface requirements.
  • Timer-driven scheduling combined with interrupt-based event handling for responsive control.
  • Continuous monitoring across the full operating range of both sensor and actuator.
  • External driver circuitry designed where the actuator required more power than the MCU could source directly.

Development Process

  • Selected the correct peripheral interface (GPIO/ADC/UART/I2C/SPI) based on the specific sensor and actuator datasheets.
  • Built and bench-tested low-level drivers in isolation before integrating the control loop.
  • Layered timer scheduling and ISR-based event handling on top of verified drivers.
  • Validated response time and accuracy across the full operating range, not just typical conditions.

Challenges & Solutions

Challenge

Polling-based sensor checks would have introduced unacceptable response latency for real-time control.

Solution

Moved to an interrupt-driven architecture with timer scheduling, keeping response deterministic regardless of main-loop workload.

Results & Impact

The system delivered consistent, deterministic real-time sensor-to-actuator response validated through direct hardware testing across the full operating range.

Future Improvements

  • Add a communication interface to report status to a host system.
  • Extend to multi-sensor fusion.
  • Add low-power sleep modes between events.