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Project Notes

#584 HPDL-1414

Test driving a retro HPDL-1414 4-digit GaAsP display with an Arduino.


Here’s a quick demo..



The HPDL-1414 is a smart, four character, sixteen-segment, red GaAsP display. The on-board CMOS IC contains memory, ASCII decoder, multiplexing circuitry and drivers.

  • Supply Voltage : 4.5-5.5V
  • Macimum current: 90mA
  • Character height: 2.85 mm (0.112”).

The real beauty of this “old fashioned” display is the immersion lens that magnifies the red GaAsP segments nicely.

Module Connection

Function HPDL1414 Pin Arduino Pin
D5 1 D7
D4 2 D6
!WE 3 A0
A1 4 A2
A0 5 A1
Vcc 6 5V
D0 8 D2
D1 9 D3
D2 10 D4
D3 11 D5
D6 12 D8






Using the HPDL1414 Arduino Library.

The character set is quite limited, and custom glyphs are not supproted


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.