Roland SPD30 MIDI extension

I have this Roland SPD30 digital percussion pad and Alesis DM6 electronic drum kit. I like SPD30 sound and that you can customize it to your needs. Roland pads are nice, but you cannot play them like real drums. But you can expand it using external pads and hi-hat control. Unfortunately, there are only 4 inputs, so you can only set up, for example, hi-hat, snare, kick, and ride. I wanted to have a full drum experience, so I came up with a solution.

The Roland SPD30 also has MIDI input (DIN5 and USB). With a bunch of laying around electronic components, I have built a MIDI extension. Basically, it's just 4 analog inputs on Arduino (protected with a diode and resistor) that are connected to piezo triggers on Alesis DM6 pads. There is even a dedicated Arduino library for this called HelloDrum. Another useful library is the Arduino MIDI library, which lets you send MIDI data using a UART serial interface. I'll be testing this design now for a few days. I like the way all parts came together to fit in a small enclosure that's been collecting dust for many years.