Circuit Bent Roland TR-505 - Touchscreen Controlled Solid State Patch Bay with Memory
Channel: Charles Werbick
Date: 2014-12-25

Short demo of the solid state patch bay I built for circuit-bending drum machines and synthesizers. This video is more of a preview of things to come than a 'how-to', mostly due to me not knowing in advance whether ANY of this would work... (Note - If you don't care about any of this and just want to hear the finished result, then check out the video here- http://youtu.be/nu6FfKYgT78 )

The circuit I built has 384 analog switches in a 48x8 array. This allows 8 different patches or 'bends' using ANY of the connected bend points to be active at any given time. It is controlled by an Arduino Mega via a touchscreen and a 4x4 keypad. Hooking this up to the tr-505 was a proof-of-concept. This particular patch bay will actually be going into a TR-626. But I didn't want to brick a 626 if my design was bad. So I tested it on a $25 TR-505 first and I'm extremely pleased with the results. The way I designed the software, no two active patches can share a patch point. Conflicting patches are muted. (I'm also going to add manual mute/unmute buttons for each bus.) This makes it easier to create and save complex configurations. Speaking of saving, bends can be saved to EEPROM with 64 user memory slots accessible via the 16 key pad. The Arduino can also receive 'instrument change' messages to change to any of the saved favorites via MIDI in. So I can now save and recall circuit bends at the touch of a button, or activate them via MIDI! Also all bends are 100% reversible. If I clear all of the switches, it goes completely back to 'stock' sound. So it is a stable mod, which is nice. (Goodbye Patch Cables!!!)

Note- For the curious - the Touchscreen and RA8875 driver board I'm using come (as does the library that accesses it) from http://www.adafruit.com. I recommend them highly for projects like this. They work hard to support the hardware that they sell and provide libraries and examples too.