TRS-80 Model 100 Gets Arduino Heart Transplant

When [Stephen Cass] identified himself with a damaged Tandy TRS-80 Design 100 moveable computer system, the most basic option was to purchase an additional broken a person and make just one working laptop from two non-working desktops. Even so, this remaining him with a dilemma — what to do with the (now even much more) damaged a single remaining about?

Obviously, he did what a lot of us would do and utilised contemporary hardware to interface with the primary components that still get the job done. In this case it intended changing the motherboard with an Arduino Mega 2560.

Luckily, the Design 100 has a substantial fanbase and there is a good deal of beneficial information and facts offered on the web, like the comprehensive assistance manual, that assisted [Stephen] to fully grasp how to travel the uncommon display.  The Liquid crystal display has a resolution of 240×64 pixels, which are broken down into eight zones of 50×32 pixels, and two zones of 40×42 pixels.  Just about every zone is then further more divided into four financial institutions, 8 pixels tall, so that each individual column of eight pixels corresponds to a single byte.

Every 1 of the ten zones is managed by an specific High definition44102 driver IC, linked to a 30-little bit wide bus for deciding on the proper chip, bank and column.

With the Arduino managing the information, the outdated Liquid crystal display nonetheless necessary a -5 V provide for distinction and an RC filter to smooth out the PWM signal [Stephen] is applying to modify the viewing angle.

With the new interface, [Stephen] is capable to access all of the pixels on the first display, and to use present day graphics libraries these as displayio. With the display screen problem solved, he intends to use a different Teensy 4.1 to join with the keyboard matrix and provide a VT100 terminal interface.

Upcycling aged, broken hardware can be a good deal of fun and is normally educational.  Knowing why particular structure choices had been built at a time when the engineering trade-offs were unique can lead to insights that are right relevant to contemporary models when resources get restricted. In this circumstance, the quirky Liquid crystal display drivers had been a reaction to making the show of text as effective as possible, so as not to overburden the processor.

The TRS-80 personal computers are ripe for hacking, with their “built-for-service” designs, and we’ve featured a couple of in the past.  Some have replaced the motherboard with one thing more recent, like [Stephen], whereas other folks have also changed the display, or linked them to the cellphone network.

Have you located new approaches to get old components working? Tell us in the opinions down below or ship us a message on the Hackaday guidelines line.

Many thanks to [nb0x0308] for the idea!