A Z80 Micro TV Clock

The guts of a Z80 MicroTV Clock

As an adventure in computer history, [Len] built up a clock. The Z80 Micro TV Clock brings together a homebrew computer and three Micro TVs into a rather large timepiece.

The computer powering the clock runs the CP/M operating system. This OS was eventually released as open source software, and a variety of homebrew computer projects have implemented it. This clock is based on an existing breadboard CP/M machine, which includes schematics and software.

With an OS running, [Len] got a text editor and C compiler working. Now custom software could be written for the device. Software was written to interact with a Maxim DS12885 Real Time Clock, which keeps the time, and to output the time to the display controllers.

The Micro TVs in this build are Sony Watchman displays featuring a 2″ CRT. The devices had no video input port, so [Len] ripped them open and started poking around. The NTSC signal was found by probing the board and looking for the right waveform.

To drive the TVs from CP/M, a custom video driver was built. This uses three relatively modern ATmega328P microcontrollers and the arduino-tvout library. All of these components are brought together on a stand made from wood and copper tubing, making it a functional as a desk top clock

8 thoughts on “A Z80 Micro TV Clock

  1. There’s something about the strange anachronistic combination of technologies that appeals to me. CP/M, Arduino, old analog TVs, new ATmega processors, all held together with a frame soldered out of copper plumbing pipes and fittings!

    It’s certainly not the most practical or simple method of building a clock, but if you have to ask “why”, I suspect you’re missing the point.

  2. This is a pretty cool build but I can’t help but think that you could do the entire project with a single Parallax Propeller, emulating the Z80 to run CP/M, and generating all three TV signals with nothing outside the chip but some external RAM and a few resistors.

    1. Then what would be the point of sticking with Z80 architecture or running CP/M? Or even driving these televisions with it? At that point, it would be “easier” in terms of parts and labor to just hook a propeller chip to a set of OLED displays. Or an arduino, for that matter.

      The thing that’s impressive and elegant about this thing isn’t that it’s a clock, or even that it can run CP/M. What’s impressive is that this is a full computer system that he soldered together from scratch, and that it not only works, but that it is actually capable of running a popular operating system to boot. He didn’t just grab a computer-on-a-chip like a microcontroller, he build the computer from scratch and not only dos it run, but it even fits together into an aesthetically pleasing (retro) form factor.

      1. Well getting a Z80 to run isn’t much harder than using a microcontroller if you use static RAM. I wasn’t dissing the project, but in a sense it’s really a couple of projects glued together; using the vintage Micro TV’s is kind of a separate thing from hacking the Z80 to life, and while the result is cool neither half of the project seems like the world’s best fit for the other.

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