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SD card multi-cart for the Atari 2600 (based on my UnoCart design)
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robinhedwards v1.05 Atari 7800 Compatibility
change to menu and some cartridge emulations to support Atari 7800.
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firmware v1.05 Atari 7800 Compatibility Mar 31, 2018
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pcbs/cartridge_slot_breakout add breakout pcb Jan 27, 2018
source v1.05 Atari 7800 Compatibility Mar 31, 2018
LICENSE Initial commit Jan 27, 2018 update versions Mar 19, 2018
UnoCart-2600-Manual.pdf update manual Mar 21, 2018


The UnoCart-2600 is an open source SD-card multicart for the Atari 2600. Use the joystick or the SELECT/RESET keys to navigate the SD card and select a title to play.

SD card should be formatted as FAT or FAT32.

The UnoCart-2600 can emulate most banking schemes with ROM sizes up to 64k and RAM sizes up to 32k. (more description to follow)



The UnoCart-2600 is based on my earlier UnoCart project for the Atari 8-bit. It can be built using a STM32F407 DISCOVERY board connected to a small PCB to breakout the Atari 2600 cartridge signals.

An article describing how to build an UnoCart for the Atari 8-bit was published in Excel Magazine issue #4. You can also get a PDF of the article here.

Building the cartridge for the 2600 is almost identical, with the same connections between D0-D7 and A0-A12, +5V and GND. All the other connections to the breakout PCB can be skipped, since these signals are not present on the 2600 cartridge slot.

Obviously, you'll need a breakout board designed for the 2600 cartridge slot rather than the Atari 8-bit. The design files for the breakout PCB are hosted here and can be used to make your own copy of the PCB.

Remember to program your DISCO board with the UnoCart-2600 firmware, rather than the UnoCart firmware.

(better building instructions to follow)

The UnoCart-2600 menu can be set to display in NTSC, PAL or PAL60 as follows:

  • By default, the firmware will be NTSC.
  • Connect PC0 -> GND for PAL60
  • Connect PC1 -> GND for PAL

Note that this is for the menu only, and has no effect after you have selected a cartridge to play.


Custom PCB

I have also designed a custom PCB for the UnoCart-2600 pictured here. This is mainly to make it easier to get people to test the design. The PCB design files are not currently public.

Front of PCB when inserted in Atari Back of PCB when inserted in Atari


The UnoCart-2600 firmware is open source under a GPL license and is hosted here.


  • Design, hardware and firmware by Robin Edwards (electrotrains at atariage)
  • Additional work on firmware by Christian Speckner (DirtyHairy at atariage)
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