About BoxLambda

BoxLambda is a project that creates a retro-style FPGA-based microcomputer from open-source components. The microcomputer serves as a platform for both software and gateware experimentation.

Current Features

• Targets the Arty-A7-100T FPGA development board.
• Ibex RISC-V core with machine timer and hardware interrupt support.
• Interrupt shadow register bank supporting low-latency interrupt handling.
• Stable low-latency access to internal memories and registers. Stable and documented instruction cycle counts.
• 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.
• Dual YM2149 PSG Audio.
• SD Card Controller and FatFs File System.
• 24-pin GPIO, UART, SPI Flash Controller, I2C Controller.
• Real-time Clock and Calendar (RTCC) support.
• USB HID Keyboard and Mouse support.
• Picolibc-based standard C environment.
• DFX Partial FPGA Reconfiguration support.
• Test application suite covering all SoC components, running on FPGA and Verilator.
• Linux CMake and Bender-based Software and Gateware build system.

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 allowing for a mix-and-match of software and hardware components. Optionally, support Partial FPGA 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 (April 2025)

• Infrastructure (build system, etc.): Complete.
• Gateware: Complete and meeting requirements.
• Software: Early stage development.

GitHub

• Source Code: https://github.com/epsilon537/boxlambda/
• Project Blog: https://epsilon537.github.io/boxlambda/
• Project Documentation: https://boxlambda.readthedocs.io/en/latest/