https://github.com/project705/nixie

RaspberryPi Nixie Tube Calculator Clock w/Android Control
https://github.com/project705/nixie

android nixie nixie-tube-clock raspberrypi

Last synced: about 1 month ago
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RaspberryPi Nixie Tube Calculator Clock w/Android Control

• Host: GitHub
• URL: https://github.com/project705/nixie
• Owner: project705
• License: mit
• Created: 2021-09-03T06:15:43.000Z (almost 5 years ago)
• Default Branch: main
• Last Pushed: 2021-09-03T22:09:25.000Z (almost 5 years ago)
• Last Synced: 2025-01-30T00:27:55.088Z (over 1 year ago)
• Topics: android, nixie, nixie-tube-clock, raspberrypi
• Language: C
• Homepage:
• Size: 847 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# Nixie Tube Calculator Clock w/Android Control



There's nothing quite like basking in the soothing orange glow of a

cold-cathode nixie tube display. An excellent vehicle for aforementioned

basking is the Singer/Friden

[EC1117](http://www.oldcalculatormuseum.com/friden1117.html) calculator.

Released in 1971, this beauty sports a full dozen Hitachi

[CD-90](http://www.tube-tester.com/sites/nixie/dat_arch/Hitachi_catalog.pdf)

nixie tubes. Given the pervasive nature of modern computers, however, the

EC1117's number crunching capabilities may seem somewhat modest and its

portability limited (despite the convenient carrying handle).

Surely you are now thinking precisely what I am: this calculator should be

turned into a clock; a clock controlled by an Android app! Ask and 'ye shall

receive! Below you'll find a write up describing the transformation and also

links to full source code, 'scope traces, schematics (those are kinda rough

since I don't have the calculator schematics), packaging info and more. Let me

know if anything seems missing.

If you want to skip right to the details:

*   First [watch the demo](https://www.youtube.com/watch?v=mibd44goZ-E)

*   Then [see these slides](http://epieye.com/nixie/nixie_calc.pdf) which give an overview with pictures, oscilloscope traces, schematics and more

*   Read more in the [Hackaday writeup](https://hackaday.com/2016/07/15/45-year-old-nixie-calculator-turned-udp-server/)

*   Get the code [from github](https://github.com/project705/nixie)

* * *

Instead of watching TV I modified my EC1117 to function as a programmable clock

and digital display. This was achieved by using an oscilloscope to reverse

engineer the display interface of the EC1117. Once I understood the interface

signaling and protocol, I used a couple of 4504 level shifters to connect it to

the GPIO bus of a Raspberry Pi 2B. Then I wrote a small C program to emulate

the bus protocol in software. The program busy polls the calculator's 860Hz

system clock waiting for a rising edge. Once the edge is found, it outputs a

serial bitstream across the 4-wire bus to produce the desired display output.

The C code also creates a thread listening for UDP packets. This thread decodes

a simple ASCII protocol that allows wireless network clients to change the

clock mode (e.g. different date/time formats), and also allows setting each

individual digit to an arbitrary value.

Part of this project was an experiment to see if it was possible to emulate

such a protocol without a real-time operating system. The answer seems to be

mostly yes, it is possible although one can observe a few glitches here and

there. Presumably this is due to being descheduled and missing the next edge

due to an inconvenient context switch. Note that the code itself always busy

waits to minimize context switch overhead. Also the clock I'm using from the

EC1117 board appears to be the system clock; its period is about 20 bittimes.

This means the emulation timing is open loop for all those bittimes, so timing

jitter will be most visible on the uppermost digits (i.e. furthest from the

system clock edge).

Another objective was writing an Android app to control the clock and display.

This was a way for me to learn about app development. The main app activity

uses an image of the calculator manufacturer's dataplate as the anchor for a

fling gesture. Swiping this image to the right increments the display mode

while swiping left decrements the mode. The activity also contains 12 wheel

controls, each mapping to a single digit on the EC1117. When in arbitrary

display mode the user can set the calculator digits in real-time using these

wheels. Each increment of a wheel results in an event which sends a UDP packet

to the calculator resulting in a change of the corresponding digit on the nixie

display. Users can manipulate multiple wheels simultaneously and all digits

will smoothly update. There is also a configuration utility to set the IP

address and port. I might eventually get rid of this in favor of full

zero-configuration with UPnP, mDNS and friends.

      Nixie Tube Poetry:

         i once met a Clock in Dixie

         who lit up its Digits with Nixie

         keeping Time with a Pixie

         while Drinking a Moxie

         why is Life so Boxie?

      Nixie Tube Poetry by Gabe:

         Amber digits dance

         Calculate, enumerate

         Dozen nixie tubes