BoxLambda is a hardware-software crossover project creating an experimental, retro-style, FPGA-based microcomputer. The goal is to create a new computer to explore old ideas.

The Physical Setup

The physical setup. The physical setup.

Current Features

  • Target FPGA: Arty-A7-100T.
  • Ibex RISC-V core with machine timer and hardware interrupt support.
  • Harvard architecture-based interconnect.
  • Low-latency register and memory access across the SoC.
  • Predictable instruction cycle counts.
  • DFX Partial FPGA Reconfiguration support (OS support TBD).
  • DDR3 external memory access through the Litex memory controller.
  • OpenOCD-based debug access on FPGA and Verilator.
  • VERA-based VGA graphics: 2 layers, tile or bitmap mode, 2 banks of 64 sprites, 128KB Video RAM, 256 color palette, Forth supported.
  • Dual YM2149 PSG Audio (OS support TBD).
  • SD Card Controller and FatFs File System.
  • 24-pin GPIO, UART, SPI Flash Controller, I2C Controller (OS support TBD).
  • Real-time Clock and Calendar support (OS support TBD).
  • USB HID Keyboard and Mouse support (OS support TBD).
  • SoC test suite covering all components, running on both FPGA and Verilator.
  • Software Test suite covering all OS features, running on FPGA.
  • BoxLambda OS: Mecrisp-based Forth software environment with C FFI (WIP).

Gateware Block Diagram

BoxLambda Gateware Block Diagram.

Software Block Diagram

BoxLambda OS Architecture. BoxLambda OS Architecture Block Diagram.

Key Goals

  • Create a sandbox for experimenting with software and FPGA gateware:
    • It should be easy to jump in and do something: create, hack, tinker.
      • Simple Enough for One Person: A motivated individual can develop a solid understanding of the entire system, including software and hardware.
      • Deterministic Behavior: The duration of operations such as internal memory or register access must be predictable by design.
      • Self-Contained Run-Time Environment supporting high-level interactive and low-level systems programming.
    • Create a Modular Architecture that allows software and hardware components to be mixed and matched, with optional support for FPGA Partial Reconfiguration.

  • Target Hardware: Digilent’s Arty-A7.

  • The computer supports the following peripherals:
    • USB HID Keyboard
    • USB HID Mouse (optional)
    • USB HID Joystick (optional)
    • Real-Time Clock and Calendar (optional)
    • Serial port
    • SD card storage
    • Flash Memory storage
    • VGA Display
    • Audio output
  • Sound and graphics support retro-style 2D demos and gameplay.

Status (October 2026)

  • Infrastructure (build system, etc.): Complete.
  • Gateware: Complete and meeting requirements.
  • Software: Development ongoing.
    • BoxLambda OS Forth Environment: Development ongoing.
    • Forth<->C FFI: completed.
    • Filesystem layer: completed.
    • Graphics layer: completed.

Changelog

Documentation