This device is intended for people who wish to play their physical game cartridges using an emulator. Use this cartridge reader to back up rom images from atari2600 game cartridges. Rom images can be played on an emulator such as Stella.
I have printed the new connector design. I am pretty pleased with the result, but I felt the connector was sticking out of the panel too much, so I recessed it. It looks more like the original cartridge connector of the atari2600 now.
I have done some testing with the STM32duino USB bootloader. A bootloader enables the user to upgrade the firmware of the cartreader via USB without the need for a special programmer. The bootloader is active after the device is powered up or when the reset button is pressed. dfu-utlil can be used to flash on the firmware.
The "Blue Pill" STM32 board I am using ships with a UART bootloader. I want to make the device firmware user-upgradable over USB, so I will put a USB bootloader on it instead. Currently the firmware only supports reading functions, but I can add writing support in the near future.
I designed the bottom half of the enclosure. It features a cutout for the usb connector and some hidden cutouts that are covered by two layers, which can be opened up with a knife to reveal debug headers, reset switch and status leds. Right now I am making these with my home printer, but I might have these made with a fancy SLA printer.
The PCBs I have received are usable, but I would like to do a second revision to fix some things e.g. add silkscreen on both sides, make the trough holes slightly larger.
Some games contain extra hardware that allows for larger games. The game ROM is split up in banks of 4KB (or less), which can be selected by accessing specific memory addresses. The software only supports regular 4KB games and some 8KB games published by Atari. I will add support for some other bankswitching schemes, but I cannot test all of them with physical cartridges. Kevin "Kevtris" Horton made a list of atari games and which bankswitching schemes they use. See Kevtris List of Atari2600 games. (This is really impressive)
I have not designed the bottom part yet, as it is not required to test the functionality. It merely serves to protect the electronics. The two halves will either snap together or be fastened using self tapping screws.
The housing is 3d printed. I can print these at home, order them from a third party or users can choose to print their own. STL files will be available.
I chose to use a pre-built STM32 board, which should require less hand soldering than a custom PCB. The STM32 blue pill boards are very cheap, however they require some work to get them to function properly. The USB connector is soldered on very poorly, so I had to add some more solder to make it stronger. The USB pullup resistor R10 has a wrong value of 10k and I replaced it with the correct 1.5k. I have had issues in the past with the programming header, so I reflowed those pins while I was at it. The boards come without populated male headers, so I soldered those on.
A few weeks ago I ordered adapter pcbs, which connect the STM32 board to the cartridge connector. These just arrived and I soldered up a proto.
Putting it together
The first thing I noticed when putting the thing together was the yellow jumpers sticking out on the bottom. (I could have foreseen this in CAD.) If I flip the board around I save a few mm. This means the housing can be smaller -> cheaper.
To connect the STM32 to the cart edge connector I designed a small adapter board. It is designed to screw into the back of the connector housing. It contains some female headers. I placed a solder jumper to connect shield ground to the ground plane. It would be possible to place a small surface mount inductor here. I have ordered 10 of these PCBs, which contain 40 adapter boards in total.