Retrode SMS/GG plug-in adapter pin-out

Posted 2 months ago

Okay then, this is the pin-out for the Master System / Game Gear plug-in adapter. Not sure if this is exactly the same as the final production version that Matthias is making, but its the same as the prototype and it works!

As each system uses a different cartridge pin numbering scheme, I have made up a few images to help make it (hopefully) obvious for each one.

With all three of these PCB’s, I have considered the side with the components mounted as the front as it is the side that faces the side of the cartridge case with the label.

• Tags:
• Sega
• Mega Drive
• Master System
• Game Gear
• Retrode
• Retrode SMS/GG plug-in adapter

Retrode SMS/GG plug-in adapter follow up

Posted 3 months ago

I have been going through my Game Gear and Master System games, trying them out with the SMS/GG Plug-in adapter and have noticed two things:

1. The Game Gear connector needs to be secured.
2. Game size detection is a little flaky.

Game Gear connector - Every time you insert/remove a Game Gear game, the connector moves a bit as it is only secured by the solder joints. Now this might not seem like much of an issue, but over time, it could cause the solder joints to fail. In the Game Gear, the connector is held in place with two rivets (see photo below), the plug-in adapter could do with two holes to secure it in a similar way. I mentioned it to Matthias and he said that the production Adapter will have such holes, perfect.

Game Gear PCB

Game size detection - The first few cartridges I tried with the adapter worked fine, the resulting ROM files were the correct size and they loaded straight up in an emulator. As I tried more, I started to notice that some of them were not working, mainly because the ROM files were smaller than they should be. Lets take Super Monaco GP as an example, it is a 256KB cartridge which the Retrode makes a 128KB ROM file from.

It isn’t the Retrode that’s at fault here, its the cartridge (or the games programmer).

The SMS/GG ROM header has a location that specifies the ROM size (0x7FFF), and it turns out that quite a few games (seems to be mostly games larger than 128KB from my experience) don’t have the correct size there, they have a smaller size listed. The Retrode looks here to work out what size to make the ROM file, and if it is wrong in here, the file you get is the wrong size and doesn’t work. In this instance, Super Monaco GP has $F (128KB) at 0x7FFF, which is wrong (it should be $0 (256KB).

Super Monaco GP SMS header screenshot (location 0x7FFF highlighted)

Luckily, the Retrode is a clever beast. As of firmware v0.16a, there has been an overdump function. The HWB button cycles between auto size detection and 3 predefined ROM sizes. Using this feature I set the size to 256KB, and what do you know, I had a working ROM file! I was able to get all the other non-working games to work using the same method.

It won’t be a problem with every game you use, but it is something to bare in mind when using this adapter.

• Tags:
• Sega
• Mega Drive
• Master system
• Game Gear
• Retrode
• Retrode SMS/GG plug-in adapter

Final testing of Retrode Master System / Game Gear adapter

Posted 4 months ago

Well I finally got my adapter back from Matthias (postage times are way longer during the Christmas holiday) and there was a surprise in the box! Along side my mess of wires was a nice PCB and a couple of 50 way Master System edge connectors. Matthias had taken my mess of wires and turned it into a PCB with mounting holes for both a 50 way Master System edge connector, and a 50 way Game Gear connector.

As it was not a final product, the edge of the PCB was not chamfered so I filed along the edge to make it easier to insert in to the Retrode cart slot. Next, I soldered the connectors to the board, Master System on the front, Game Gear on the back.

First off I tried a master system game (Wonder Boy). I plugged it in to the adapter which in turn I plugged into the Retrode 2. Nothing happened. I took the cart out, cleaned the contacts and tried again. Still nothing. So I tried a Game Gear game (Columns), which did exactly the same. I decided to leave it until I could email Matthias to see if I was missing something.

Before I got round to it, Matthias sent me an email to say that I would need to bridge two points on the PCB for cartridge detection to work, specifically, the two points marked with Xes (pin 19 on the Master System and a pin 32 on the PCB edge). I had noticed these when I was soldering the connectors in and wondered if something needed to be one with them. I joined the points with a length of wire and tried again. Bingo, a file appeared on screen (generic name as master system headers don’t contain the game name) which loaded in my emulator. Sorted. I guess this wire won’t be necessary when the adapters are released, the link will be added to the board.

All the Master System games I tried worked straight off, as did most of the Game Gear games, a couple needed a clean and one didn’t work at all, Fantastic dizzy. This is a Codemasters game and they used their own mapper chip which handles things differently to the Sega ones. It is documented, so maybe Matthias will be able to add compatibility in a future firmware version.

Can’t wait to see the final version of the adapters, it’s been great fun being part of the process :)

• Tags:
• Sega
• Mega Drive
• Master System
• Game Gear
• Retrode
• Retrode SMS and GG adapter

Initial testing of Retrode Master System / Game Gear adapter

Posted 7 months ago

After my success with the Virtual Boy Retrode adapter, I decided to try making another for some of my other cartridges that weren’t already catered for. This time I opted for the Sega Master System. As Game Gear games are near enough the same as Master System games data-wise (you can play master system games on a Game Gear with a converter), I thought I would try to make a dual system adapter.

Following the same procedure as with the Virtual boy adapter, I located the Master System and Game Gear cartridge pinouts and matched them up with the relevant pins on the Mega Drive connector, first for the Master System, then for the Game Gear. There were a few differing signals, but I matched up the main ones.

Next job was to remove the ROM chip from a donor Mega Drive cartridge and start the tedious process of attaching wires to the vacant holes. I use individual strands of wire from an old Ultra DMA IDE/ATA cable for this (like the one on the left in this picture), it’s single strand and just the right thickness.

Cartridge connectors next. Master System turned out to be simple, I de-soldered an ISA card socket from an old motherboard and cut it down to size, same pin pitch and board thickness, sorted. The Game Gear proved to be more difficult. The pins on the edge of a Game Gear cartridge are arranged in offset parallel lines, so finding a suitable replacement for a real one proved to be impossible. I didn’t fancy destroying my fully working (even the sound!) Game Gear, so got a faulty one off of ebay for next to nothing and de-soldered the cartridge socket.

I soldered the Master System connector on, connected a game and plugged it in the Retrode. A quick check of the resulting file in a hex editor showed that it was reading something, and after comparing it to a reference ROM, it was almost the same, albeit with additional FF’s. This was because the Retrode is expecting 16bits of data, and the Master System is only 8bits, so the upper 8bits were empty, something for Matthias to sort in the firmware.

The Master System uses Frame Control Registers (FCR’s) to access the ROM, so the Retrode would need to be able to do the same. Matthias sent over a couple of test firmwares to try out, but unfortunately, the only cartridge we got to read correctly was Transbot, which is a 32KB cartridge, so didn’t use any FCR swapping.

Unable to resolve the issues, Matthias asked if I would be willing to send my adapter to him to continue testing, which I of course did. Now he has a working firmware, and is getting some boards made up based on my prototype! Make sure to order one when he gets them in.

Talking with Matthias before I sent off the adapter, I wondered if the Game Gear could be put on the higher 8bits of the Mega Drives 16bit data lines, enabling both Master System and Game Gear cartridges to be plugged in at the same time. He said it would be possible, but it would interfere with the auto detection. He has since mentioned that he is adding space to solder on a Game Gear cartridge connector to his adapter PCB, so hopefully he worked out a way round this. I will post the pinout for the adapter when I find out how Matthias has added the Game Gear to it.

• Tags:
• Sega
• Mega Drive
• Master System
• Game Gear
• Retrode
• Retrode SMS and GG adapter