EZ Flash Jr Patcher

Each file is checked against known hashes before and after the patch. Source and docs

Kernel Safe option

The kernel is the ezgb.dat file on your microSD card. Stock files come from EZ Flash: the 1.04e / FW4 package on their download page (EZ-FLASH Junior), or the 1.05e FW5 2021-9-18 package.

Choose or drop the stock ezgb.dat from your firmware package

Kernel	Stock SHA-1
1.04e	43c76dc2b206907a68a1b3d320324d2d4438b7f3
1.05e-0918	d575f6379d2b9a7acbae12d9cfe7bed7adb4b2ff

Firmware updater Experimental

THIS CAN BRICK YOUR CART.

All firmware updaters for the EZ Flash Jr, stock or modded, carry a small risk of bricking the cart if the update doesn't go smoothly. A bitstream that fails its CRC is caught by the cart's own fallback image, but a bootloader that runs and then hangs cannot be fixed with another updater: recovery needs hardware, an SPI programmer on the flash chip or JTAG. This firmware has run on one FW4 and one FW5 Jr. Only flash it if you accept losing the cart.

Use a fast, good-quality microSD card and fresh batteries (or a plugged-in, charging console), and do not power off while the updater writes. A Game Boy Advance SP is not recommended, since it's too easy to bump the cart and interrupt the update; if it's your only option, be extremely careful. EZ Flash's FW5 is itself a release candidate: on slow SD cards it can halt at LOADING or OS INIT. If you don't need what the firmware adds, use the kernel above and stop there.

What it adds: a new boot screen, fast launch straight from the bootloader (the game named by FLAUNCH= in /EZGB.CFG, START at power-on cancels), the pending save backed up before a fast launch (never when the battery is dead), Super Game Boy detection (untested on a real Super Game Boy; it takes over from the kernel's SGB BOOT box, which is tested, so on an SGB use the kernel alone for now), and on FW5 the MBC3 game clock and fast loading.

I understand this rewrites my cart's firmware and can brick it. Choose or drop the stock updater (Update_FW4.gb or Update_FW5_2021-9-18.gb)

Installing:

Install the kernel above first.
Copy the patched updater to the card, launch it from the file browser like a game, and press A. Wait until it says it's done.
Power off and on. The boot screen's bottom line reads FW4-MOD or FW5-MOD and the mod's version.

Going back: run EZ Flash's official updater for your firmware the same way.

Updater	Stock SHA-1
Update_FW4.gb	d61bc32c41a378be491eced4244a84abe7c84d7c
Update_FW5_2021-9-18.gb	46464fe0393bd212668d82519a874edf88f10b67

The FW5 patch needs Update_FW5_2021-9-18.gb from the 2021-9-18 package. The 2020-7-31 FW5 updater is not supported.