This repository houses the ModRetro Chromatic's FPGA design files.

For more information about the ModRetro Chromatic, please see visit ModRetro.com.

This project builds upon the open source work provided by the Game Boy MiSTer project. When checking out this repository, make sure to run the following command as this repository submodules the Game Boy MiSTer project.

git submodule update --init --recursive

The Gowin FPGA Designer v1.9.9.03 must be used. Using Gowin IDE v1.9.10.X or newer is currently not supported by this build.

You will also need to apply for a local license with Gowin through their website: https://www.gowinsemi.com/en/support/license

The license expires after one year and will require reactivation.

You will receive an email within a few minutes with a .lic file attached. Run the Gowin IDE and install the license when it prompts you. You'll need to close and re-open the GOWIN IDE if everything was successful.

Once in the IDE, load evt1_x2.gprj project and click on the green recycle-like button icon to run synthesis and PnR. This will take about 5-10 minutes to complete.

Flashing can be performed using the official Gowin Programmer software or the openFPGALoader utility through the Chromatic's USB interface. The Gowin Programmer requires the installation of the GWU2X device driver.

Note:

1. The Chromatic must be powered on for either tool to detect the FPGA. This means the power switch is in the ON position.
2. If using openFPGALoader, the tool must be compiled with support for the Gowin GWU2X cable.

Detect the Chromatic FPGA While Powered On

openFPGALoader --detect --cable gwu2x

You will see an output similar to:

empty
User requested: 6000000 real frequency is 6000000
index 0:
        idcode 0x1281b
        manufacturer Gowin
        family GW5A
        model  GW5A-25
        irlength 8

Flashing the Chromatic

openFPGALoader --write-flash --cable gwu2x --reset <file>

Here, <file> refers to the generated bitstream file. This file can be found at esp32t/impl/pnr/evt1_x2.fs.

When modifying the RTL design, please also update the 14-bit FPGA version within [esp32t/src/rtl/BSP/system_monitor.sv] around line 384 (see version).

This will ensure you can always using the ModRetro Update Tool to restore your Chromatic to the latest official release.

Please submit all issues and bug reports through our Contact Form.

• GOWIN Semiconductor
• MiSTer

• [rayjt9] For their palette improvements to the BootROM.