Z80 Retrocomputing 12 – Talking Nixie Tube Clock

In this post, I assemble a bunch of RC2014 boards and make a talking Nixie Tube Clock

This project Makes use of the following RC2014 boards:

Here’s a diagram of how the boards all work together:

Talking Nixie Tube Clock, Diagram

I chose to use a UP501 GPS module so that the clock can set itself from GPS, rather than requiring me to manually set the time. That’s the one part of the clock that doesn’t fit the “retro” theme, since it is a modern GPS module. Alternatively, the clock can be operated from a BQ4845 real-time clock chip, which would be more fitting with the retro theme.

The SIO/2 board provides the TTL-level serial port that talks to the GPS, as well as a port for console. There’s no real need for a console, other than debugging. Since the GPS module operates at 2400 baud, I needed a baud rate generator, and that’s the purpose of the CTC board.

Speech synthesis is provided by an SP0256A-AL2 speech synthesizer chip. The speech synthesizer board also includes a general-purpose input port, which I use to implement the front panel buttons. One momentary switch is used to announce the current time.

We also need RAM and ROM. I ran out of backplane slots, so I used my dual RAM/ROM board.

Here are a couple high-resolution pictures of the completed clock:

RC2014 Talking Nixie Tube Clock, Front View

RC2014 Talking Nixie Tube Clock, Top View

The software is written entirely in assembly, and is available in my github repo at https://github.com/sbelectronics/rc2014.

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