An LCD mounted inside a Roland synthesizer

Reverse-Engineering A Display Protocol To Repair A Roland Synthesizer

Repairing digital gadgets isn’t as difficult as it employed to be. Thanks to the online, it’s simple to come across datasheets and software notes for any common ingredient inside your gadget, and when you’ve located the defective 1, you merely purchase a replacement from just one of a million world-wide-web shops — assuming you never conclusion up with a fake, of study course. When it arrives to non-conventional factors, however, matters get extra hard, as [dpeddi] observed out when a good friend requested him for aid in repairing a Roland Juno-G synthesizer with a broken show.

The main issue in this article was the fact that the display screen in dilemma was a custom made design, with no alternative or documentation available. The only matter [dpeddi] could determine out from the support guide was the primary pinout, which confirmed a parallel interface with two lines labelled “chip select” — an indication that the exhibit contained two different controllers. But the specific protocol and info structure was not documented, so [dpeddi] introduced out his logic analyzer to consider and decode the signals produced by the synthesizer.

Immediately after a bit of demo and mistake, he was able to determine out the protocol: it appeared like the exhibit contained two KS0713-style Liquid crystal display controllers, every single controlling just one 50 % of the screen. Acquiring a compatible substitute was continue to proving tough, so [dpeddi] determined in its place to decode the first signals utilizing a microcontroller and exhibit the photo on a modern-day Lcd driven by SPI. Right after some intial experiments with an ESP32, it turned out that the process of reading through two reasonably rapidly parallel buses and driving an even more rapidly serial a single was a little bit much too significantly for the ESP, so [dpeddi] upgraded to a Raspberry Pi Pico. This labored a take care of, and many thanks to a 3D-printed mounting bracket, the new show also in good shape snugly inside of the Roland’s case.

The Pico’s code is available on [dpeddi]’s GitHub web page, so if you’ve also bought a dodgy show in your Juno-G you can just download it and use it to plug in a brand-new show. Even so, the approach of reverse-engineering an present exhibit protocol and translating it to that of a new a person is really universal and should come in helpful when doing work with any style of electronic gadget: say, a classic calculator or multimeter, or even an additional synthesizer.

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