Roland’s Alpha Juno 2 is an analog, polyphonic synth made in the mid-80s. While it isn’t as capable as the massive synths made around that time, it was very influential synth for the techno scenes of the late 80s and early 90s.
[Jeroen] is lucky enough to have one of these synths, but like all equipment of this era, it’s showing its age. He wanted to replace the character LCD in his Alpha Juno 2 with an OLED display. The original character LCD was compatible with the Hitachi HD44780 protocol, and still today OLEDs can speak this format. What should have been an easy mod turned into editing hex values on the EEPROM, but he still got it to work.
While the original character LCD could display one line of 16 characters, the ROM in the synth didn’t know this. Instead, the display was organized as a 2×8 display in software, with line one starting at address 0h, and line two starting at 40h. For a drop-in replacement, [Jeroen] would need a display the characters organized in this weird 2×8 format. None exist, but he does have a hex editor and an EEPROM burner.
With the Alpha Juno’s firmware in hand thanks to someone who does a few firmware hacks to this synth, [Jeroen] had everything he needed. All that was left to do was going through the code and replace all the references to the second line of the character LCD.
After burning and installing the new ROM, the OLED display was a drop-in replacement. That meant getting rid of the whiney EL backlight in the original display, and making everything nice and glowy for a few nights on a dark stage.
Will this work on all Generation 1, 2, and 3 synths? http://fallout.wikia.com/wiki/Synth
lol *facepalm* ICWYDT
Indeed, more and more the word ‘synth’ is being used to describe an artificial human. And I too was a fraction of a second in confusion because of that.
Addendum: I’m wondering now what the colloquial for self-driving cars will become once those get in common use.
I have an 1×16 lcd that also arranges the characters in 2×8. I think they were pretty common back in the day.
I was going to say that I’ve encountered these as well. They’re a bit quirky to work with, but not that obscure.
I had a few of those lying around somewhere. Pulled out from some old Alcatel desk phones.
I mean the control part isn’t entirely rocket science, but you’ve got to admit, it is a bit quirky. The only question is, there must be a hell of a reason for that.
The 8×2 layout (i.e. 40×16) could run on just the HD44780 by itself without any additional drivers, because the HD44780 itself had 16 common drivers and 40 segment drivers. Larger displays had to use extra ICs to add extra segment drivers.
Anyway, how’s the brightness halflife of OLEDs doing now? Surely better than the EL, but…
Interesting
Excellent hack, sir!