Project: Real Time 3-Band EQ Filtering

Links

• Project Proposal
• Interactive 3-Band EQ Simulator
• IIR Filter Math and Calculations
• Midpoint Checkoff
• Final Report

Overview

This project implements a real-time 3-band equalizer that can independently adjust low, mid, and high frequencies of an audio signal. Audio is input via a 1/8-inch auxiliary cable, digitized by an ADC, processed on an FPGA, and output through a DAC to stereo speakers.

Three potentiometers allow live control of each frequency band, enabling hands-on EQ adjustment with minimal latency.

Features

• Three adjustable bands:
  • Low: ~100–400 Hz
  • Mid: ~400 Hz–2 kHz
  • High: ~2–8 kHz
• Real-time digital filtering on an iCE40 UltraPlus FPGA
• MCU-controlled filter coefficients sent via SPI
• Stereo input/output using I²S protocol
• Bypass mode preserves original audio when knobs are neutral

Hardware

• iCE40 UltraPlus FPGA
• STM32L432KC MCU
• PCM1808 ADC
• PCM5102 DAC
• 3 x potentiometers for EQ control
• Standard 1/8-inch audio input

Usage

1. Connect an audio source to the ADC.
2. Adjust low, mid, and high potentiometers to modify EQ in real time.
3. Audio output is sent to speakers via the DAC.