OpenTyrian Pocket

A bare-metal, native port of OpenTyrian for the Analogue Pocket, running directly on a VexRiscv RISC-V soft-core CPU instantiated on the Pocket's Cyclone V FPGA.

The core is a fork of PocketDoom. See README_POCKETDOOM.md for details on the underlying core.

Features

• Pixel-Perfect Video: Tear-free, double-buffered rendering at the original 320x200 resolution
• FM Synthesis: Uses a hardware OPL2 block (via jotego/jtopl2) for AdLib/SoundBlaster music synthesis.
• High-Fidelity Effects: Digital PCM sound effects are processed through a custom 64-bit linear interpolator with a 4-pass FIR anti-aliasing filter, upsampled to 48kHz interleaved stereo. We even added 6dB of software headroom to eliminate the nasty clipping found in the original DOS game!
• Console-Optimized UI: Tweaked UI to avoid Keyboard input and unnecessary options.
• Save Support: Persistent config, and storage for 10 saves.
• Gamepad Support: All inputs are mapped natively to the Pocket's face and shoulder buttons.
• Analogizer Support: Play on a legit CRT with the Analogizer!

Controls

Button	Action
D-Pad	Move Ship / Navigate Menus
A / B	Sidekick Left / Right Weapons
X	Primary Fire
Y	Change Weapon Mode (if available)
R1	Secondary Weapon Mode
Start	Enter / Accept / Start Game
Select	Escape / Back / Menu / Pause

Controls can be remapped in-game.

Installation

You will need the original Tyrian v2.1 DOS data files. These are legally available as freeware.

1. Copy the dist package to the root of your Analogue Pocket SD Card.
2. Download the officially-sanctioned game data used by OpenTyrian: http://camanis.net/tyrian/tyrian21.zip
3. Extract the contents of the ZIP file to a folder on your computer.
4. Use the provided Python script to pack these files into a single .rom file for the Analogue Pocket:

   python3 bundle_rom.py /path/to/extracted/tyrian21 tyrian.rom

5. Copy the resulting tyrian.rom into your Assets/tyrian/obsidian.PocketTyrian/ folder on your Analogue Pocket's SD Card.

##Building from Source

To build the firmware yourself, you will need a standard RISC-V GCC toolchain (specifically riscv64-unknown-elf-gcc with multilib support). You will also need the Intel Quartus FPGA tools to rebuild the bitfile with the corresponding bootloader image.

1. Clone this repository.
2. Ensure you have the opentyrian source submoduled in third_party/opentyrian.
3. Navigate to the firmware directory:

   cd tyrian-pocket/src/firmware

4. Build the binaries:

   make clean && make -j

5. The resulting tyrian.bin is the engine executable that the bootloader runs.
6. Copy the generated bootloader firmware.mif to ./src/fpga/core/firmware.mif
7. Recompile the Quartus project, reverse the resulting bitstream, and copy to the core directory.

Technical Details & Architecture

This port is technically a fork of PocketDoom.

• The system uses a two-stage boot process: a tiny bootloader in FPGA BRAM loads the 300KB tyrian.bin engine and the 11MB tyrian.rom asset package from the SD card into the SDRAM.
• The file system (libc/file.c) intercepts engine fopen calls and routes them to either the read-only asset ROMFS in SDRAM or the read-write nonvolatile RAMFS used for configuration and save games.

License

• The OpenTyrian engine is licensed under GPL2
• The PocketTyrian bootrom code is licensed under MIT
• See README_POCKETDOOM.md for licensing of the RTL and other components.

Credits & Acknowledgements

• The OpenTyrian Team: For keeping this classic game alive and accessible.
• ThinkElastic / PocketDoom: For providing the high-quality reference VexRiscv architecture and Analogue OS bridge framework that made this port possible.
• Jotego: For the jtopl2 FPGA module used to synthesize the soundtrack.
• Dyreschlock: For the tyrian.bin platform image used for the core.
• RndMnkIII: For adding Analogizer support to the core.