Atari 5200:Controller Adapters
During its lifetime and especially in recent years, the Atari 5200 became notorious for its complex and unreliable stock controller. It is no surprise then that a number of controller adapters have been developed for the 5200, allowing for all sorts of controllers to be used. Several aftermarket controllers also exist, which provide greater reliability and player comfort than the original controllers.
Wico Command Control Joystick and Keypad
In 1983, joystick manufacturer Wico produced an aftermarket joystick for the 5200 as part of their Command Control range. This joystick is simply a recolored version of the Computer Command joystick previously released for the Apple II computer, and features an actual analog stick with both self-centering and non-centering modes for both axes. While meant for the 5200, it uses a DE-9 connector and cannot be plugged directly into the 5200 itself. To rectify this and to allow for use of the 5200's keypad functions, a special Y-adapter was included with the joystick. This Y-adapter plugs into the 5200 console and has both a DE-9 connector for the joystick and a DB-15 connector for an original 5200 controller. Wico also released a Command Control keypad, which can completely take the place of the Y-adapter as it has a built-in DE-9 connector. Both controllers currently command high prices on the used market, with the keypad going for significantly more due to its rarity.
Competition Pro
Coin Controls Ltd. produced a version of their famous Competition Pro joystick for the 5200 in 1983/84, which uses a digital joystick and two independent fire buttons. Unlike the Wico joystick, it can be plugged directly into the 5200 and has a passthrough DB-15 connector so an original 5200 controller can be connected for its keypad functions and analog joystick.
Masterplay Interface
Sold by Electra Concepts in 1984, the Masterplay Interface is the only controller adapter released for the 5200 during its heyday. It is a small box that connects to the 5200 and has three ports. One of them is a DE-9 port for 2600-compatible joysticks and another is a DB-15 which is a passthrough for an original 5200 controller, which is needed for the Start/Pause/Reset buttons and keypad; a switch is also included to completely enable the 5200 controller for games which require its analog joystick. The third port is a simple 3.5 mm mono jack located in between the two controller ports, intended for an additional fire button that could be adhered onto the controller of one's choice.
MegaPlay
The MegaPlay adapter is compatible with Sega Genesis/Mega Drive controllers and goes a step farther than most other adapters in that it uses button combinations to simulate both keypads, meaning that it can totally replace the 5200 controller (except for games which need the analog joystick). Though it is not commercially available, the PCB project is available on OSH Park. It is based around an Arduino Nano and a couple of 4052 multiplexers.