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Stephen Cass’ Upcycled TRS-80 Mannequin 100 Makes use of an Arduino Mega 2560 as a Show Driver

IEEE Spectrum’s Stephen Cass has saved a traditional transportable pc from the scrap heap due to some intelligent upcycling, turning a damaged TRS-80 Mannequin 100 into an Arduino Mega 2560-powered customized terminal.

“How laborious might or not it’s to swap out a 40-year-old 8-bit 8085 CPU and motherboard for one thing extra trendy,” Cass asks, rhetorically, in a retrospective of the work carried out on his challenge up to now — work which is ongoing with a view to finally construct the system as much as a contemporary multi-core Linux field.

The reply: moderately laborious, in case you’re trying to retain the unique LCD panel, which sits above the transportable’s keyboard to supply what was at its launch in 1983 an impressively-capable system for computing on-the-go. “The M100’s LCD is actually 10 separate shows, every managed by its personal HD44102 driver chip,” Cass explains. “The driving force chips are every accountable for a 50-by-32-pixel area of the display screen, besides for 2 chips on the right-hand facet that management solely 40 by 32 pixels.”

Utilizing a useful service handbook, the HD44102’s datasheet, and different classic computing fans’ efforts in the identical subject, Cass was in a position to join the LCD to the Arduino Mega and show arbitrary photos — turning the Arduino into, successfully, a monochrome show driver accepting bitmap inputs and formatting them as required.

“The LCD can now be hooked as much as the microcontroller of my selection by way of a parallel or serial connection to the Mega, which copies incoming knowledge to the framebuffer,” Cass explains. “I intend to make use of a Teensy 4.1, which can permit me to speak to the matrix keyboard straight, have sufficient compute energy for some fundamental text-editing firmware, and supply a VT100 terminal serial interface—which may very well be to a Raspberry Pi 4 Compute Module additionally mounted contained in the [Model 100]. That would offer Wi-Fi, a 64-bit OS, and as much as 8 gigabytes of RAM—a giant step up from the 8 to 24 kilobytes that the case initially housed!”

Overhauled or re-imagined TRS-80 Mannequin 100s are a standard sight within the maker world: 4 years in the past Trammell Hudson used a Teensy++ microcontroller board to interchange a defective motherboard, and like Cass reused the unique show by some intelligent coding, whereas pseudonymous maker “belsamber’s” tackle the improve noticed the inventory display screen changed with a contemporary ultrawide able to working two full-width terminal side-by-side. The core TRS-80 design, in the meantime, has impressed units from the Clockwork Pi DevTerm, now obtainable in a RISC-V-powered variant, to the chunky READY! Pc Mannequin 100.

Cass’ full write-up, together with hyperlinks to the service handbook and different assets, is offered on IEEE Spectrum now.



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