MIDIBox SID Project Blog
Enter the Matrices
The MB-6582 control surface is based on wiring matrices that it allow it to use less DIN (digital in) and DOUT (digital out) ins and outs. Since I'm making my own control surface I can either direct wire everything or make my own matrices. From what I learned online there are not enough ins/outs on the MB-6582 so I'd have to make additional modular ones, so I decided to go the matrix route. It'll be a pain in the ass, but certainly a learning experience. One of the most common places to find a wire matrix is in a computer keyboard. This allows the keyboard to have more keys than it does wires going to the computer. Here's a Wikipedia article about it that explains how it works.
I need to make two matrices. One for the switches and another for the LEDs. Each switch requires a diode before or after it to make sure the electricity only flows in one direction. LEDs are diodes themselves, so we don't need additional diodes for that matrix.
I'm using perfboards for my matrices. There are schematics for the DIN (PDF) and DOUT (PDF) on the MIDIBox site. The DOUT PDF has two schematics, but the one that goes to JD6 on the MB-6582 PCB is for the modulation matrix (the grid of LEDs and buttons) that I'm not including in my control surface, so that one I will ignore. Below you'll see the two mockups I made of the matrices.
I'll be using a lot of little jumper wires to connect everything, but the biggest pain is going to be just getting the components tacked down so they don't fall out when I solder them. One of the leads from each diode on the DIN matrix needs to connect to the lead on my pin header. I want to avoid as much resoldering as possible, though its going to be hard to avoid. There's not much space between the diodes and the pin headers, but the headers are quite taller than the diodes so its very difficult to tape both down at the same time. My current plan, which may change once I start soldering, is to first add all the diodes, but to only initally solder the cathode end (the lead that doesn't connect directly to the pin header) with the assumption that will be enough to hold them in place. Then I'll add all the pin headers and start soldering those and the jumper wires.