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|The Learning Circuit|
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In 1982, the Atari 5200 was Atari’s answer to competing consoles such as the ColecoVision and the Intellivision. It’s basically an Atari 400 computer that was repackaged as a game console. Ben unscrews the case from the bottom of the case. As his first computer was an Atari, he knows what to expect. It’s going to be MOS Technology 6502 game system. He removes the RF shield to get to the main circuit board. He recognizes the Mask ROM due to its reduced pin count but he’ll need to look up and mark the rest of the chips.
The CPU is a custom version of the 6502 MOS chip, the ROM boots the system, POKEY which is a potentiometer keyboard controller, the ANTIC chip works as a graphic controller for the display, and the GTIA chip receives data from the ANTIC and adds sprites if applicable before sending the stream to your television. It contains 8 RAM ICs at 16 kb which act collectively as one word of memory. Ben looks up the schematic to find out how the POKEY chip interfaces with the controller ports. He points out the audio and video circuitry which is used to take digital signals and convert them to analog so they can become an RF signal to go to the RF adapter on your TV.
Ben goes to work on designing a controller in Autodesk Fusion 360. The board has an Atmega 328 and translates the analog joystick values to a digital potentiometer, providing a range that matches the analog signals which the console can interpret. The board has an Analog Devices AD5242 dual potentiometer on it. Next they are going to take a modern joystick and convert its values into something the Atari can understand by using the Arduino IDE.