GTFX

FPGA-based guitar effects processor implemented in SystemVerilog for the Xilinx Arty A7-100T. Processes 24-bit/48kHz audio in real-time through a configurable chain of four classic effects.

Signal Chain

I2S RX -> [Tremolo] -> [Phaser] -> [Chorus] -> [Delay] -> I2S TX

Each effect can be independently bypassed via hardware switches.

Effects

Effect	Style	Key Parameters
Tremolo	Optical/Fender	Rate (0.5-12 Hz), depth, waveform (sine/triangle)
Phaser	MXR Phase 90	Speed (0.5-5 Hz), 4-stage all-pass, optional feedback
Chorus	BOSS CE-5	Stereo output, rate, depth, 2-band EQ
Delay	Boss DD-3	Up to 1s, tone control, feedback

Hardware

• Board: Arty A7-100T (xc7a100tcsg324-1)
• Audio: I2S interface on Pmod JA (24-bit, 48 kHz)
• Control: UART (115200 baud) for parameter updates, 4 switches for effect bypass
• Clocks: 100 MHz system, 12.288 MHz audio (via Clock Wizard)

Pin Mapping

Function	Pmod/Port	Signals
I2S TX	JA upper	MCLK, LRCLK, SCLK, DATA
I2S RX	JA lower	MCLK, LRCLK, SCLK, DATA
UART	USB	TX (A9), RX (D10)
Switches	SW0-SW3	Tremolo, Phaser, Chorus, Delay enable
LEDs	LD0-LD3	Mirror switch states

Prerequisites

• Xilinx Vivado Design Suite
• Arty A7-100T board
• I2S audio codec connected to Pmod JA

Build

make proj        # Create Vivado project and generate Clock Wizard IP
make bitstream   # Run synthesis, implementation, and bitstream generation
make prog        # Program the FPGA
make sim         # Run testbenches in XSim
make open        # Open project in Vivado GUI
make clean       # Remove build artifacts

UART Command Interface

Connect via serial terminal at 115200 baud. The command processor accepts hex-encoded parameter updates for each effect. Responses are echoed with OK or Err status.

Arty> <command>
OK

Project Structure

src/           SystemVerilog source modules
  top.sv         Top-level module and signal chain
  tremolo.sv     Tremolo effect
  phaser.sv      Phaser effect
  chorus.sv      Chorus effect
  dd3.sv         Digital delay effect
  i2s2.sv        I2S protocol driver
  uart.sv        UART transceiver
  cmd_proc.sv    Command parser and parameter registers
  audio.sv       Audio interface wrapper
  volume.sv      Volume control
sim/           Testbenches
tcl/           Vivado build scripts
constrs/       XDC pin constraints

License

Apache License 2.0