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The Joey Junior GB/GBC/GBA cart dumper and flasher

Joey Jr User Manual:

Beginners guide:

  1. Clean your carts where possible. Dirty contacts can cause unreliable Save and ROM extraction. A cotton tip with some Isopropyl alcohol will go a long way. If you have a tri-wing screwdriver or gamebit, you can open the shell and give it a proper clean. If you don't clean your cart, there is risk of corrupting your save file.
  2. Insert your game cart into the Joey Jr
  3. Insert your USB-C cable into the Joey Jr.
  4. Your cart will appear as a USB drive on your PC like below.

  • You may not see the same files as above, RTC.SAV for example will only appear with game carts which have a Real Time Clock built in.

POKEMON.GBC is the ROM file. This is the game code that runs on your console. You can run this in an emulator on your PC too directly from the cart, or you can backup the files on your PC for safe keeping.

POKEMON.SAV is the save game file. This is where your progress is stored when you 'save' when playing on your console. This too can be used in an emulator or backed up for safe keeping.

To write your Save file back onto your cart you simply drag the file to the BENNVENN drive on your PC. Joey Jr will instantly replace your old file with the new one ready to use on your console. No need to delete or rename filenames, Joey will know what to do with the file.

The other files can be ignored for this beginners guide. They are explained further below in the advanced section.

Handy Tip! - Copy your ROM and Save file to a folder on your PC and open the ROM in an emulator (I recommend BGB) to confirm the save extracted correctly.

GameBoy Camera

  1. Clean the contacts.
  2. Insert the camera in the orientation shown above.
  3. Insert the USB-C cable into your Joey Jr.
  4. Your camera will appear as a USB drive on your PC like below

All your images are instantly available to access - Even if you have deleted them in the past! If they haven't been overwritten, they'll be on there.

Handy Tip! - You can plug the Joey Jr directly into your smart phone for instant access to your images on-the-go! Instagram and other social media apps can access the images directly from the camera!

Advanced Guide:

There are hundreds of hours of coding combined in the latest firmware to bring features not available in any other cart interface. These aren't always visible but once you know they're there, they'll make life sooo much easier when working with the Joey and your carts.


One of the ways to communicate with your Joey Jr is through this file. The most frequent command you'll give Joey is UPDATE. This is required before Joey will accept his new FIRMWARE.JR file. Joey requires uppercase in all its commands.

You may notice whenever you save MODE.TXT your Joey will restart and re-connect to your PC. This was a feature coded early on to save wear and tear on the USB-C connector on the Joey and your PC/Phone etc... When swapping carts just open MODE.TXT and hit Ctrl-S, or File>Save and Joey will restart, detect what cart you have inserted and Joey will set himself up.


This is Joey's way to talk to us. Inside DEBUG.TXT we'll find some handy information like what Firmware version Joey is using, Where to find firmware updates, links to our Discord if you need help or want to chat about new things we're working on and then onto the steps Joey is taking to determine what is plugged into it, how best to access the ROM and RAM, If the cart is a Bootleg cart that can be re-flashed, What voltage the cart is being supplied, Game information and a quick Checksum to see if Joey has read the cart correctly.

Checksum Correct/Invalid - We've coded in a little ROM check which tests the header is read correctly. If you cart is dirty or Joey doesn't have a good connection to the pins, you'll see 'Checksum Invalid' inside DEBUG.TXT. This is an indication that you'll need to clean or reconnect the cart. When an Invalid Checksum is detected you will also see MODE.TXT turn into MODE!.TXT for a quicker indication something isn't right. 


This is a very large list of all the GBA games we could find information on. This is used whenever you plug a GBA cart into the Joey. It tells the Joey the ROM size, and the type and size of save medium used in the cart. Nintendo used quite a few different types and the easiest way to have a sure-fire way of selecting the right type is using this lookup table. Most carts are in there, some of the rarer carts may not be, in this case Joey gives you ALL the possible save types as files. You can add your rare cart to the ROMLIST file. We'll cover this in the Expert guide below.


To update Joey's firmware, it is first required to write UPDATE in all caps, at the beginning of the mode.txt file. Joey will then accept new firmware files. NOTE: ONLY USE FIRMWARE FILES PROVIDED FROM THE JOEY JR PRODUCT PAGE IN STORE. NEVER COPY FIRMWARE FILES FROM ONE JOEY TO ANOTHER, OR USE BACKUP FIRMWARE FILES FROM YOUR JOEY.

Bootleg / Chinese / Repro Gamecarts

Joey has some pretty advanced cart and Flash detection algrithms coded in. For most carts, you just plug them in, open Debug and check that Flash is detected

All you need to do is make sure your ROM is equal or smaller to the cart capacity and drag it onto the BENNVENN drive. Joey will do the rest. If you cart is not supported or you're having trouble flashing it, head over to our discord and we'll quickly add support for it. We're buying a few dozen bootlegs a month to stay up to date on what China is producing. We also have a bootleg FAQ.

Battery-less Carts

It is not common to find a modern bootleg out of China with a battery fitted. While many original games used batteries to store the progress of your save, Chinese engineers have instead used a spare area of the Flash ROM to store this data. The down-side is that the ROM must be patched to make use of this ROM area. Most bootlegs out of China have the games patched for this already. As a consequence, you can't access the save file like you would with a genuine game cart. Until now!

As of Firmware V2_22 Joey now includes a Gameboy emulator coded in! This was necessary for us to run your bootleg code directly from the cart, find where the game is storing its save data in the ROM and direct Joey to it so you can drag and drop your save files like any other original game cart. This is still in beta testing though most bootlegs we've tried have been detected and work! You can finally backup your original Pokemon save onto your bootleg cart without having to search for save data fragments in the bootleg ROM and copy/paste byte by byte.

Nintendo Power Cart

We fully support the only official Nintendo Flash Cart! To access the NPC cart, write NPC into MODE.TXT and save. You'll get a file list similar to what you see below

You can use the awesome online ROM generator by OrangeGlo (Link in debug.txt) to compile some of your favorite games to fill the 1mbyte capacity of these carts. The generator will give you two files, the ROM and the MAP file. Copy the ROM file, disconnect, reconnect and then the MAP file and your cart is ready to use!. PLEASE backup your original ROM and MAP file, these can be extremely rare and valuable - Consider preserving them in our Discord.


A work in progress...