• Another Atari 5200 controller adapter concept

    12 hours ago 0 comments

    MegaPlay adapter lets you play Atari 5200 using a 6 button Sega Genesis controller yet providing full keypad control.

    The circuit can be built using an Arduino Nano and two analog multiplexers. Interface with analog joystick can be borrowed from "Low Priced MasterPlay clone adapter".

    Keypad presses can be emulated by activating a pair of analog multiplexers. This scheme allow the simulation of 1 (one) keypress at a time, but frees the software from critical timing. 

    Buttons can be mapped as follows:

  • Atari 5200 controller adapters

    11/25/2019 at 02:48 0 comments

    The Atari 5200 controllers are well known by its low reliability. Many alternatives to the original controllers have rose along the time  from when the sytem was being sold on stores up to present days when it is possible to find adapters being produced and sold by members of Atari Age community forums. The adapters found today can be either:

    a) analog - based on digital potentiometers or

    b) digital - based on switched resistors.

    Both change resistance in a RC network that is used by the console to convert a time measurement into positional information.

    There are other ways to do it, though:

    1. Applying a variable voltage on a fixed resistor. The charging time depends upon the RC constant for a given potential difference (voltage). That is pretty much how the trackball works.
    2. Detecting the moment the timing capacitor start to charge and hold the voltage low until the correct timing has passed. On the 5200 it is a tricky task, because the capacitors do not receive a pulse (of known time) to discharge. Instead they are held discharged until the CPU generates a pulse internally that releases the charge.

    I have figured out the methods above after went through plenty of technical information such as datasheets, books and forum posts. In the meantime I have worked on the design of some alternative controller adapters:

    Norris: Adapater for Wii Nunchuck controller.

    • Provides vertical/horizontal movement plus 2 buttons. - Keypad functions are provided by tactile switches. - Body composed by 3 PCBs stacked on top of each other
    •  Built-in Wii Nunchuck connector on PCB
    •  Wire bridges on PCB to hold game faceplates

    Hunter: Adapter for Playstation Dualshock controller.

    • Provides vertical/horizontal movement plus 2 buttons - Analog sticks can work together or expand to a second connector (for Robotron)
    • Directional D-PADs work behave like digital controller on Masterplay adapter
    • Numeric Pad emulated by the controller by pressing L2. Worth to mention that emulating the keyboard can be somewhaty tricky too.
    • Can emulate behavior of trackball, behaving like the Trackpoint on Thinkpads

    Stingray: Adapter for Wii Nunchuck Classic controller

    • Basically the same functionality of the Hunter
    • Numeric Pad emulated by the controller by pressing ZL
    • Built-in Wii Nunchuck connector on PCB

    Concept board for StingRay

    Second controller (for dual stick games) is connected through P2 Jack. If necessary GND connection wire can be used for one of the triggers of the second controller.

  • Emulating a potentiometer for the Atari 5200

    10/28/2019 at 23:30 0 comments

    So far the controller adapters I have seen for the Atari 5200 and that can provide analog control use a used a digital potentiomenter (and extra capacitance). 

    This is certainly a nice solution but there are other alternatives, though:

    1) Keep series resistor constant, vary the voltage applied to charge the capactor (just like the trackball do)

    That can be done with a PWM providing 0-5V and some resistors in a network to match the desired voltage range. This method is used on the CX-53 trackball. 

    2) Detect when capacitors start to charge and hold the line down until the desired count, then push the line to +5V

    It is a pity that the architecture of the Pokey Chip, used by the Atarti 5200 to read the potentiometers do not discharge the capacitors at the beginning of the sampling cycle but at the end. The only mark of the beginning of the charge is that the voltage over the capacitor starts to ramp up and that can be done by the analog comparator of a microcontroller set to a voltage that is below the minimum Vih (1.9V). Luckly there is plenty of time to react to that, as the pokey counts in Hsync lines (64us ).