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I'm looking into hacking my digital alarm clock to be able to control it with my Raspberry Pi A+. It has a typical 4 digit screen (7 segment) with two dots in between.

The screen has a brand and printed on it, but no luck finding any information on this Japanese website.

The screen communicates with 14 pins, I have no other information. How would I go about trying to power it and control it through GPIO pins ? Is it feasible?!

Close up of connector
Back of screen

  • WRT feasibility you might want to have a look at this Q&A and this article. – goldilocks Jun 22 '15 at 14:52
  • You will need to either reverse engineer the display or find a datasheet. My guess is that you won't find datasheet so you will need to try to reverse engineer it. – Craig Jun 22 '15 at 17:04
  • I had a look at the manufacturers page - to save others the effort, it's in Chinese for the most part. – Mark Williams Jun 23 '15 at 8:06
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Typically, this type of display has a matrix of 7 segment drives x 4 character selects, and probably another pair for the colon; there may well be an am/pm indicator. It can be common anode or common cathode.

You will need a 3V battery & a sensible resistor (320 or thereabouts) or some such to provide around 10mA to an individual LED, and try pins & note which combination lights which segments, + polarity; it soon becomes clear how it's wired. You can then play with drive currents & establish the right resistors (x7) to light it properly.

After that, it's relatively easy!

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  • Thank you for your response. I have been looking around online, what is all this talk of multiplexing ? I have a basic understanding of what it is / how it works, but it's still very superfluous. Your simple suggestion seems to overstep it. Do I need to understand multiplexing to get it to work? – user1107703 Jun 23 '15 at 17:57
  • You use the 4 lines of the matrix, one at a time, to select a digit; you set the 7 lines that control the segments, to match the selected digit. That way you drive 28 segments with 11 pins. – Mark Williams Jun 24 '15 at 7:34

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