CB FI 420

Circuit Break Podcast #420

The Mega IIe: A Vintage Computing Adventure with James Lewis

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March 5, 2024, Episode #420

We dive into the intricate world of vintage computing with James Lewis, aka the Bald Engineer, who takes us through the journey of constructing a functional computer based on the Apple II GS's Mega II chip. He shares his nostalgic connection to the Apple II series, revered for its open design and pioneering hardware engineering. Our conversation spans the detailed architecture and challenges of his Mega IIe project, from initial concepts to the complexities of integrating modern microcontrollers like the RP2040 during pandemic component shortages. Tune in for a fascinating journey from the past to the future, bridging vintage computing with modern technology!

🚨Contest Announcement 🚨: Introducing a new Circuit Break contest! This contest is themed around building food-related electronic projects. We’re offering over $5,000 in cash prizes, themed trophies, and free prototyping from MacroFab. The deadline to submit is March 31st, 2024. Thanks to Mouser Electronics for sponsoring the contest prizes!

Discussion Highlights

  • The Mega IIe Project: James built a functional computer around the Mega II chip from the Apple II GS, containing the logic of previous generations of Apple II computers.
  • Nostalgia for the Apple II: James shares his personal connection to the Apple II, and explains why the Apple II is revered in the vintage computing space, particularly for its open design and hardware engineering aspects.
  • Technical Deep Dive into the Apple II and Mega IIe: James dives into how Apple II's open design compares to other computers of its era such as the Commodore.
  • Bit Preserve Project: His GitHub project, Bit Preserve, is where people can contribute redrawn vintage computer schematics in KiCad.
  • Architecture and Development of the Mega IIe: James outlines the evolution of the Mega IIe project from a simple breakout board idea to a complex design involving multiple boards, fly wires, and the use of modern microcontrollers like the RP2040 due to component shortages during the lockdown period.
  • Debugging Challenges: Difficulties encountered when integrating components and understanding undocumented features, such as the keyboard signals and slot communications.
  • Design Approach (Rev 2): A backplane system where individual blocks of the Apple II design were isolated into separate cards, allowing systematic troubleshooting and incremental progress, which significantly facilitated debugging.
  • Video Signal Processing: Explored the challenges and solutions in handling video output, particularly transitioning from composite video to digital video using the Mega II chip's RGB output.
  • Rev 3 Development: The transition from a modular backplane system (Rev 2) to a single board computer (Rev 3), consolidating all functions and addressing issues like power supply design.
  • Future Directions and Learning: Reflects on the initial underestimation of the project's complexity and duration and discusses potential next steps, including the possibility of a shift in focus towards modern technology areas like machine learning for edge devices.

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About the Hosts

Parker Dillmann
  Parker Dillmann

Parker is an Electrical Engineer with backgrounds in Embedded System Design and Digital Signal Processing. He got his start in 2005 by hacking Nintendo consoles into portable gaming units. The following year he designed and produced an Atari 2600 video mod to allow the Atari to display a crisp, RF fuzz free picture on newer TVs. Over a thousand Atari video mods where produced by Parker from 2006 to 2011 and the mod is still made by other enthusiasts in the Atari community.

In 2006, Parker enrolled at The University of Texas at Austin as a Petroleum Engineer. After realizing electronics was his passion he switched majors in 2007 to Electrical and Computer Engineering. Following his previous background in making the Atari 2600 video mod, Parker decided to take more board layout classes and circuit design classes. Other areas of study include robotics, microcontroller theory and design, FPGA development with VHDL and Verilog, and image and signal processing with DSPs. In 2010, Parker won a Ti sponsored Launchpad programming and design contest that was held by the IEEE CS chapter at the University. Parker graduated with a BS in Electrical and Computer Engineering in the Spring of 2012.

In the Summer of 2012, Parker was hired on as an Electrical Engineer at Dynamic Perception to design and prototype new electronic products. Here, Parker learned about full product development cycles and honed his board layout skills. Seeing the difficulties in managing operations and FCC/CE compliance testing, Parker thought there had to be a better way for small electronic companies to get their product out in customer's hands.

Parker also runs the blog, longhornengineer.com, where he posts his personal projects, technical guides, and appnotes about board layout design and components.

Stephen Kraig
  Stephen Kraig

Stephen Kraig is a component engineer working in the aerospace industry. He has applied his electrical engineering knowledge in a variety of contexts previously, including oil and gas, contract manufacturing, audio electronic repair, and synthesizer design. A graduate of Texas A&M, Stephen has lived his adult life in the Houston, TX, and Denver, CO, areas.

Stephen has never said no to a project. From building guitar amps (starting when he was 17) to designing and building his own CNC table to fine-tuning the mineral composition of the water he uses to brew beer, he thrives on testing, experimentation, and problem-solving. Tune into the podcast to learn more about the wacky stuff Stephen gets up to.

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