TRS-80 Product 100 Receives Arduino Heart Transplant

When [Stephen Cass] identified himself with a damaged Tandy TRS-80 Model 100 portable personal computer, the most basic alternative was to acquire one more broken one particular and make a single doing the job computer from two non-operating personal computers. Even so, this remaining him with a predicament — what to do with the (now even a lot more) broken one left about?

Liquid crystal display layout is uncommon by modern-day conventional, but optimized for speedy updates

Naturally, he did what a lot of us would do and utilized modern-day components to interface with the authentic areas that continue to perform. In this circumstance it meant changing the motherboard with an Arduino Mega 2560.

Fortunately, the Model 100 has a considerable fanbase and there is a whole lot of useful details out there on the internet, such as the in depth support guide, that assisted [Stephen] to have an understanding of how to push the unusual display screen.  The Lcd has a resolution of 240×64 pixels, which are damaged down into eight zones of 50×32 pixels, and two zones of 40×42 pixels.  Each zone is then even more divided into four financial institutions, eight pixels tall, so that every single column of eight pixels corresponds to a one byte.

Each individual a single of the ten zones is controlled by an person Hd44102 driver IC, related to a 30-bit extensive bus for deciding on the correct chip, lender and column.

With the Arduino handling the data, the previous Lcd even now required a -5 V provide for contrast and an RC filter to clean out the PWM signal [Stephen] is applying to regulate the viewing angle.

With the new interface, [Stephen] is equipped to access all of the pixels on the first display, and to use fashionable graphics libraries such as displayio. With the exhibit problem solved, he intends to use a individual Teensy 4.1 to join with the keyboard matrix and offer a VT100 terminal interface.

Schematic of the Hd44102 driver circuit

Upcycling previous, broken hardware can be a lot of exciting and is normally educational.  Knowledge why specified style conclusions ended up built at a time when the engineering trade-offs have been distinctive can direct to insights that are right suitable to modern designs when sources get restricted. In this case, the quirky Liquid crystal display drivers were being a reaction to earning the display of textual content as successful as feasible, so as not to overburden the processor.

The TRS-80 computers are ripe for hacking, with their “built-for-service” types, and we have featured a few in the earlier.  Some have replaced the motherboard with some thing more recent, like [Stephen], whilst some others have also replaced the screen, or related them to the cellphone network.

Have you located new approaches to get old components performing? Convey to us in the comments under or deliver us a message on the Hackaday strategies line.

Many thanks to [nb0x0308] for the idea!

Resource : heart-transplant/

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