NextNano - ZX Spectrum Next implementation for the Tang Nano 20K FPGA board.

Status: Early release — actively developed. Source code released.

📺 Watch The Saboteur! NEXT on NextNano in action on YouTube

Hardware Requirements

• Tang Nano 20K (Sipeed, Gowin GW2AR-18)
• USB-C Hub — an active (powered) hub is recommended
• USB Keyboard — wireless or wired
• microSD card (FAT32, with NextZXOS contents — see below)
• HDMI display and cable

Optional:

• USB mouse (emulated as Kempston Mouse)
• USB gamepad or joystick (emulated as Kempston / Left port, 4 buttons)

Preparing the SD Card

The SD card is required — NextNano boots into NextZXOS from the card.

1. Format a microSD card as FAT32.
2. Download the latest NextZXOS distribution from: https://www.specnext.com/latestdistro/
3. Extract the contents of the archive to the root of the SD card.
4. Insert the card into the Tang Nano 20K's SD slot before powering on.

Features

Implemented

• All ZX Spectrum Next features
• Joystick (left port, Kempston)
• Mouse (Kempston)
• Keyboard
• HDMI video and audio output - 50Hz and 60Hz supported

Notes & Current Limitations

• The system boots at 28 MHz. Switching to other frequency possible (F8).
• Networking is not yet implemented. Network features will require an external BL616 (M0S Dock), because the BL616 built into the Tang Nano 20K has no antenna.

Software Compatibility

All software tested so far runs flawlessly — including demoscene productions, games, BASIC programs, and utilities.

Keyboard Mapping

Spectrum Key	USB Key
Symbol Shift	Left Ctrl
Edit	Caps Shift + 1 or ~
Break	Caps Shift + Space
Cursor keys	Arrow keys

Example: to type LOAD "" at the BASIC prompt, press J, then Symbol Shift + P twice.

Function Keys

Key	Function
F1	Hard reset
F3	Toggle 50 / 60 Hz video mode
F4	Soft reset
F8	Cycle CPU clock: 3.5 / 7 / 14 / 28 MHz
F9	NMI / Multiface
F10	DivMMC NMI

Release v0.2 — Source Code Release

Building from source

To build the project, use Gowin EDA 1.9.12.03 and the provided tcl script, nextNano.tcl. The build has been tested only on Linux using gw_sh. From the source directory, run:

gw_sh nextNano.tcl

Flashing the FPGA Bitstream

macOS / Linux — use openFPGALoader:

openFPGALoader -f NextNano.fs

The -f flag writes the bitstream to the onboard flash so it persists across power cycles. Without -f, the bitstream is loaded into SRAM and will be lost on power-off.

Windows — use Gowin Programmer, included with the Gowin EDA toolchain. Select the Tang Nano 20K device, set the operation to Embedded Flash Mode → Erase, Program, choose NextNano.fs, and click Program.

Flashing the FPGA Companion

To upload the FPGA Companion firmware, use the Bouffalo Dev Cube software (provided by BouffaloLab - https://dev.bouffalolab.com/download). Select the correct firmware file and load address for your setup:

Target	Firmware File	Load Address
Onboard BL616 (internal µC)	bl616_fpga_partner_nano20k.bin	0x00000
Onboard BL616 (internal µC)	fpga_companion_TN20k_internal.bin	0x40000
External M0S Dock	fpga_companion_bl616_m0s_dock.bin	0x00000

The onboard BL616 setup requires both files to be flashed at their respective load addresses.

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Acknowledgments

NextNano stands on the shoulders of these projects:

• SpecNext Ltd. and the ZX Spectrum Next community
• MiSTer FPGA (https://github.com/MiSTer-devel/ZXNext_MISTer)
• MiSTle-Dev(https://github.com/MiSTle-Dev/FPGA-Companion)

Disclaimer

This project is not affiliated with, endorsed by, or associated with the official ZX Spectrum Next project or SpecNext Ltd.