Segment LCDs from consumer electronics have a quality that generic displays don’t: they were designed for one product. The little icons, the custom glyphs, the specific arrangement of bars and arrows — all of it was drawn for a device that no longer exists, and all of it is still there in the glass.
Jose Luis Monteiro (emsyscode) has made one usable again. He reverse engineered the display from a Sony CDX-A250 car stereo and now drives it from an Arduino, with the code on GitHub under MIT.
How it went
The panel is driven by an LC75826W LCD driver chip. The crucial break, as Hackaday notes, is that Sony used an identifiable part rather than obfuscating it or hiding the logic under a chip-on-board epoxy blob. An identifiable chip means a findable datasheet, and a datasheet turns a black-box reverse-engineering job into a protocol-implementation job.
From there it’s writing the bus interface, working out which bits in the driver’s memory light which segments — that mapping is specific to the glass, not the chip — and confirming it segment by segment.
Monteiro is explicit that this is not a universal driver library. It’s code for this display’s particular configuration. But anything else using an LC75826W now has a working reference, which is most of the value of publishing work like this.
Why this belongs on the interfaces beat
Salvaged displays are an underused material. Every dead VCR, car stereo, microwave, fax machine and hi-fi receiver contains a custom segment display that was drawn by a designer, manufactured in volume, and is now free. They’re low power, readable in daylight, and they carry a period specificity you cannot buy — a 1990s car stereo’s display looks like a 1990s car stereo, and no amount of skeuomorphic rendering on an OLED achieves that.
For artists making objects, that’s a genuinely different material from a Cheap Yellow Display. The constraint is severe — you can only show what the glass was etched to show — and severe constraints are frequently the point. A piece that can only display the vocabulary of a car stereo is a piece with something to say about car stereos.
The obstacle has always been the driver. Which is why documented work like this matters more than the specific device: every published chip-to-glass mapping converts a category of e-waste into a usable component.
Two practical notes if you’re tempted. Check the driver chip is identifiable before you start, since that’s the whole difficulty, and expect the segment mapping to be entirely yours to discover even when someone has documented the same chip.