My processor. My operating system.

ALU verification, whole-machine simulation, and FPGA demonstrations are different evidence. Tomato OS exercises keypad MMIO, tile RAM, HDMI timing, the menu loop, and the current 256 × 32-bit FPGA register file. The CPU writes an 80×60 character field over a bitmap wallpaper; a separate scanout block reads it and drives the monitor. No GPU — games are loops in asm.

The clip above is the full tour: boot into Desktop v1.2, walk the application list, and open the games people ask about first — Tetris, Snake, Racer, Sudoku, Fibonacci — all painted by the CPU and scanned out over the DVI PMOD. Same recording lives in the gallery under Tomato OS.

Controls

Five Nexys buttons wired as a D-pad through rtl/board/keypad.v. Center (N17) is Enter. One physical press emits one key event — after fixing a bench that counted hundreds of repeats from a single push (dispatch). In Sudoku, Enter cycles the digit 1…9 then blank.

Keyboard MMIO lives at 0x780000: word 0 is the keycode (reading consumes it), word 1 is the ready flag. The Nexys 7-segment display follows the last nonzero writeback or store — so it is not stuck at zero while the shell waits for a key.

Main menu

Boot splash runs once. Then Desktop v1.2: applications on the left, preview and credits on the right. Tomato OS v3.0 currently has fourteen entries, each dispatched through a jump table. Envelop is linked with its setup data and bounded remote executor.

Display contract

Framebuffer window at 0x300000 — 80×60 cells, each an 8×8 pixel tile, composited over the Ghana wallpaper ROM. One word per cell (videoout.v):

• [7:0] glyph — CP437-ish code (keycodes can be drawn directly)
• [11:8] foreground palette index
• [15:12] background palette index

Attributes with a black background fit in one ADDI — any tile with bg = 0 is 0x0FFF < 4096. Splash / wallpaper art is converted for the character field with software/os/tools/build_wallpaper.py (OS assets README).

Low memory layout

Everything an LA reaches must sit under 4096 — it assembles to ADDI rd, r0, addr. Prose and pointer tables above that line use .word label instead.

Build & run

1. Edit software/os/tomato_os.s.
2. Assemble — python3 software/assembler.py software/os/tomato_os.s -o hardware/fpga/core/tb/mem/tomato_os.mem (opcodes from tomato.v1.csv).
3. Burn — make -C hardware/fpga/core burn BOOT=tomato_os packs the image into rtl/burn/*.vh for synthesis.
4. Flash the Nexys A7 bitstream (open-source flow: Yosys · nextpnr · openFPGALoader — no Vivado).

Without hardware, print the framebuffer in simulation: make -C hardware/fpga/core os. Regression: make -C hardware/fpga/core test boots the OS image and checks menu + games. Or skip all of it: run the shipped firmware in your browser — no install, no FPGA.

Tomato OS and microcode are baked into the bitstream as literal Verilog — not loaded from SD card at runtime. After editing the asm, re-burn before synthesising.