fpga

5 Mar 2026
FPGA

FPGA Projects

Multi-board FPGA development environment. Native toolchain via oss-cad-suite; Docker images available as a fallback.

Boards

Board FPGA Clock Directory
Muselab iCESugar v1.5 Lattice iCE40UP5K 12 MHz icesugar/
ULX3S 85F Lattice ECP5 LFE5U-85F 25 MHz ulx3s/

Examples

iCESugar (iCE40UP5K)

Example Description
blinky RGB LED blinky — cycles through colours using a free-running counter
tone 440 Hz square wave output via PMOD Audio
sine_tone 440 Hz sine wave via PWM + 256-entry lookup table
uart_hello Sends “Hello, World!” repeatedly over UART at 9600 baud
sine_rgb Sine tone combined with an RGB colour wheel

granular-synth-engine (work in progress)

Stage Description
01_i2s_out I2S digital audio output
02_i2s_passthrough I2S loopback (ADC → DAC passthrough)
03_spi_slave SPI slave for control parameter updates
04_dds_synth Direct digital synthesis oscillator
05_grain_engine Granular synthesis engine

ULX3S (ECP5 LFE5U-85F)

Example Description
blinky 8-LED binary counter driven from a 26-bit free-running counter
buttons Move a single LED across the bar with directional buttons
sdcard Read a 44.1 kHz 16-bit WAV from FAT32 SD card and play via 3.5mm jack

Quick Start

Prerequisites

  • Native toolchain (preferred): oss-cad-suite installed at ~/oss-cad-suite/ and sourced in your shell
  • Docker — fallback if native tools are unavailable
  • iCESugar programmer: iCELink USB mass-storage (built into board)
  • ULX3S programmer: openFPGALoader (brew install openfpgaloader on macOS)

Build

# iCESugar
cd icesugar && make -C examples/<name>

# ULX3S
cd ulx3s && make -C examples/<name>

Flash

# iCESugar — copies bitstream to iCELink mass-storage drive
cd icesugar && ./flash.sh build/<name>/top.bin

# ULX3S — loads into SRAM (volatile, lost on power-off)
cd ulx3s && ./flash.sh build/<name>/top.bit

# ULX3S — programs SPI flash (persistent, directly via openFPGALoader)
openFPGALoader --board=ulx3s --write-flash build/<name>/top.bit

macOS iCELink note: Do not use cp or dd — macOS writes non-sequentially and breaks DAPLink. flash.sh uses cat to write sequentially. If FAIL.TXT appears on the drive, the flash failed.

Docker fallback

cd icesugar && docker compose run fpga make -C examples/<name>
cd ulx3s   && docker compose run fpga make -C examples/<name>

Project Structure

fpga/
├── icesugar/                     # iCESugar v1.5 (iCE40UP5K)
│   ├── Makefile.inc              # iCE40 build template
│   ├── icesugar.pcf              # Full board pin constraints
│   ├── flash.sh / flash.bat
│   ├── examples/
│   │   ├── blinky/
│   │   ├── tone/
│   │   ├── sine_tone/
│   │   ├── uart_hello/
│   │   └── sine_rgb/
│   └── granular-synth-engine/
│       ├── 01_i2s_out/
│       ├── 02_i2s_passthrough/
│       ├── 03_spi_slave/
│       ├── 04_dds_synth/
│       └── 05_grain_engine/
│
└── ulx3s/                        # ULX3S 85F (ECP5 LFE5U-85F)
    ├── Makefile.inc              # ECP5 build template
    ├── ulx3s.lpf                 # Full board pin constraints
    ├── flash.sh
    └── examples/
        ├── blinky/
        ├── buttons/
        └── sdcard/

Adding a New Example

# icesugar/examples/myproject/Makefile
TOP = top
PCF = myproject.pcf
SRC = myproject.v
include ../../Makefile.inc

# ulx3s/examples/myproject/Makefile
TOP = top
LPF = myproject.lpf
SRC = myproject.v
include ../../Makefile.inc

Build output goes to <board>/build/<project_name>/. Top module is always named top.

Recent Activity

  • 476fe35 add OLED waveform display and I2S passthrough examples for ULX3S (2026-03-05)
  • 9442887 document PCM5102A DAC wiring on ULX3S J1 header GN0-GN7 (2026-03-01)
  • e5fb0d0 add I2S tone and SD card WAV player examples for PCM5102A DAC on ULX3S (2026-03-01)
  • d736ff5 added ULX3S board and examples - led blinking, push button, and PWM audio our fr (2026-02-26)
  • 5e2136c add ULX3S reference copy and stripped synth-fpga-module for 50x50mm ECP5 board (2026-02-23)

Languages

  • HTML: 41%
  • Verilog: 33%
  • OpenSCAD: 16%
  • ASP.NET: 6%
  • Makefile: 1%
  • Python: 1%