Friday, January 10, 2014

All Keyed Up

Unfortunately, my Retrochallenge project continues to progress at a turtle-like pace.  I have still been waiting for parts, and tending to some of life's other demands.  In the meantime, I have managed to poke around my project at its edges...

Radio Shack ASCII-Encoded Keyboard

Keyboard Crisis

The Micro Chroma 68 board is designed to take input through a parallel interface to an ASCII-encoded keyboard.  This sort of arrangement appears to have been common in the days of TV typewriters and the Apple I.  Someone even interfaced one to the Bally Astrocade!  Nevertheless, today it seems to be quite difficult to find such hardware...

Fortunately, a couple of years back I managed to find the keyboard pictured above for sale on a popular online auction site.  FWIW, the keyboard and the PCB were sold separately in the 1977 and 1978 editions of the Radio Shack catalog.  The manual for the encoder PCB is available online for the curious among us.

Heep Test Module

Heep Test Module

I thought it would be wise to test out the keyboard, given its age and unknown condition.  Fortunately, the manual provides a diagram for the oddly named "Heep Test Module".  I was able to construct the fixture in an hour or so from a handful of scrounged LEDs and resistors, some wire, and a newly acquired edge connector.

As an aside, I thought the "Heep Test Module" name sounded a bit odd.  Coincidentally, I was reading the newly released CoCo book when I noticed mention of a Tandy engineer by the name of Jerry Heep.  I guess that "Heep Test Module" is like a printed electronics manual version of an Easter Egg!

Anyway, I'm glad I took the time to build this fixture.  Applying power to the keyboard lights-up the fixture in strange ways, revealing that the keyboard is not currently functioning as it should -- one more thing to fix...  Alternatively, I may have to buy or build some sort of replacement.

Bags Of Parts

Parts Is Parts

Aside from the keyboard situation, I am running out of excuses on the construction project.  While I still don't have all the parts I need to complete the box, delivery trucks have been rolling and I've got the bulk of the missing ingredients.  I had been missing some key parts, like IC sockets and some particularly valued resistors and capacitors.  A few of those are still outstanding, but most of the stuff is here already.

Hopefully the next post will at least have some parts stuck to the board!  Until then, of course, you'll have to stay tuned... :-)

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