TRS-80 Model 100 Gets Arduino Heart Transplant

When [Stephen Cass] discovered himself with a damaged Tandy TRS-80 Product 100 portable laptop or computer, the easiest answer was to acquire a further damaged one particular and make a single doing work computer system from two non-doing the job desktops. However, this left him with a dilemma — what to do with the (now even much more) broken 1 remaining over?

Liquid crystal display structure is abnormal by modern day regular, but optimized for fast updates

By natural means, he did what a whole lot of us would do and employed modern components to interface with the primary pieces that nonetheless work. In this scenario it meant changing the motherboard with an Arduino Mega 2560.

Thankfully, the Product 100 has a significant fanbase and there is a great deal of valuable information and facts accessible on the internet, such as the in-depth service handbook, that served [Stephen] to have an understanding of how to drive the abnormal exhibit.  The Lcd has a resolution of 240×64 pixels, which are damaged down into 8 zones of 50×32 pixels, and two zones of 40×42 pixels.  Every zone is then further more divided into 4 banking institutions, 8 pixels tall, so that just about every column of eight pixels corresponds to a solitary byte.

Every single 1 of the 10 zones is controlled by an personal High definition44102 driver IC, linked to a 30-bit large bus for picking out the suitable chip, financial institution and column.

With the Arduino handling the knowledge, the aged Lcd nonetheless desired a -5 V provide for contrast and an RC filter to smooth out the PWM signal [Stephen] is utilizing to modify the viewing angle.

With the new interface, [Stephen] is in a position to obtain all of the pixels on the authentic screen, and to use modern day graphics libraries such as displayio. With the show challenge solved, he intends to use a individual Teensy 4.1 to connect with the keyboard matrix and deliver a VT100 terminal interface.

Schematic of the High definition44102 driver circuit

Upcycling outdated, broken hardware can be a good deal of pleasurable and is often educational.  Being familiar with why specified style choices ended up made at a time when the engineering trade-offs ended up various can guide to insights that are straight related to modern layouts when methods get restricted. In this circumstance, the quirky Lcd motorists have been a response to generating the exhibit of text as successful as attainable, so as not to overburden the processor.

The TRS-80 computer systems are ripe for hacking, with their “built-for-service” types, and we have featured a number of in the earlier.  Some have replaced the motherboard with some thing more recent, like [Stephen], whereas others have also changed the show, or linked them to the cellphone network.

Have you identified new approaches to get outdated hardware doing work? Inform us in the responses under or deliver us a concept on the Hackaday ideas line.

Thanks to [nb0x0308] for the suggestion!

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