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