Status: Completed
Category: Digital Signal Processing · Embedded Systems · Real-Time Systems · Signal Acquisition · Embedded Firmware · Instrumentation
Project Type: Embedded Systems Engineering Project
Overview
The Adaptive Signal-Driven FIR Filter System is a real-time DSP platform that samples analog signals, analyzes their frequency content, and adapts its filtering behavior on the fly.
The goal was to show that meaningful digital signal processing can run on low-cost embedded hardware without a dedicated DSP chip. The system handles acquisition, frequency estimation, filter selection, and output reconstruction with minimal latency.
Unlike a fixed FIR implementation, this project adjusts the filter settings to match the incoming signal, while still allowing manual override when needed.
What it demonstrates
Adaptive signal processing on constrained hardware, with deterministic timing and low processor overhead.
Details
Objectives
- Design a real-time signal acquisition system.
- Implement interrupt-driven Analog-to-Digital Conversion.
- Achieve high sampling frequency on an Arduino Uno.
- Develop an adaptive FIR filtering system.
- Automatically estimate the dominant input frequency.
- Dynamically configure filter parameters.
- Maintain continuous non-blocking signal processing.
- Optimize processor utilization and minimize processing latency.
- Reconstruct filtered analog output in real time.
Problem Statement
Embedded microcontrollers often have limited processing power, memory, and computational resources, making real-time digital signal processing challenging. The objective was to determine whether a resource-constrained microcontroller could continuously sample analog signals, perform adaptive FIR filtering, and generate filtered outputs while maintaining deterministic timing and low processor utilization.
System Architecture
Input Signal
↓
Analog Signal Acquisition
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ADC Sampling (Interrupt-Driven, 40 kHz)
↓
Circular Buffer
↓
Frequency Analysis
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Adaptive Filter Configuration
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FIR Filtering
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Output Reconstruction
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Serial Monitoring (1 Mbps)
Hardware Components
Software Components
Embedded Firmware Responsibilities: ADC configuration · Interrupt handling · Circular buffer management · Frequency estimation · FIR coefficient selection · Signal filtering · Output reconstruction · Serial communication
Signal Acquisition
Continuously samples incoming analog signals using the internal ADC.
Sampling Frequency: 40 kHz
This sampling rate enables the system to process relatively high-frequency analog signals while maintaining stable timing.
Interrupt-Driven Design
Advantages over polling: precise sampling intervals · reduced timing jitter · deterministic execution · efficient CPU utilization · continuous operation.
Circular Buffer
Incoming samples stored using a circular buffer. Enables simultaneous sampling and processing without interrupting data acquisition. Provides continuous storage, non-blocking operation, and efficient memory utilization.
Adaptive Filter Configuration
Unlike conventional FIR filters with fixed coefficients, this system automatically adapts filter characteristics based on the detected input signal.
Responsibilities: Estimate dominant frequency · Select cutoff frequency · Generate filter configuration · Allow manual override when necessary.
FIR Filter
A Finite Impulse Response digital filter with: linear phase response · stable operation · configurable order · adaptive cutoff frequency.
The lower-order configuration provides an optimal balance between filtering performance and computational efficiency.
Output Reconstruction
After filtering, the processed signal is reconstructed and transmitted as an analog-equivalent output with real-time generation and minimal latency.
Serial Communication
Baud Rate: 1 Mbps
Purpose: Parameter monitoring · Debugging · Signal visualization · Performance evaluation
Implementation Summary
Acquisition and timing
Signal capture is interrupt-driven so sampling stays deterministic.
Key choices: ADC sampling at 40 kHz · register-level optimization · circular buffering
Adaptive filtering
The system estimates the incoming frequency, selects a cutoff, and applies an FIR filter that fits the signal instead of using one fixed configuration.
Key choices: automated cutoff selection · manual override · FIR filtering for stability and linear phase
Output and monitoring
After filtering, the signal is reconstructed for output and monitored over serial at 1 Mbps.
Key choices: low-latency reconstruction · serial debugging · continuous non-blocking processing
Results
The implementation demonstrates real-time performance while keeping processor usage relatively low.
Strengths: deterministic timing · adaptive operation · continuous processing · modular firmware
Constraints: limited memory on Arduino Uno · filter order bound by available processing power · frequency estimation depends on input quality · output resolution limited by PWM
Takeaways
Engineering lessons: interrupt handling is critical for deterministic real-time systems · circular buffering avoids blocking · register-level programming improves performance · adaptive filtering improves usability · low-resource DSP requires careful tradeoffs.
Applications
Embedded DSP education · Audio signal processing · Sensor signal conditioning · Industrial instrumentation · Biomedical signal processing · Data acquisition systems · Communication systems · Real-time monitoring
Lessons Learned
Technologies Used
Hardware: Arduino Uno
Software: Embedded C/C++ · Arduino IDE
Engineering Concepts: Digital Signal Processing · Finite Impulse Response Filters · Adaptive Filtering · Interrupt Programming · Register-Level Programming · Circular Buffers · Analog-to-Digital Conversion · Embedded Systems · Real-Time Systems · Signal Processing
Future Improvements
Project Legacy
The Adaptive Signal-Driven FIR Filter System showed that sophisticated DSP can be made practical on low-cost hardware. It strengthened experience in embedded firmware, interrupt-driven programming, real-time design, and low-level optimization, and became a foundation for later signal-processing work.