Orbit-Chroma-9

Devlog #1: Schematic Done, Moving to PCB Layout

The Vision

I’m building a 9-key mechanical macro pad powered by a Seeeduino XIAO. I’m planning to include an I2C OLED screen (hoping to get live Bongo Cat animations running on it!), a rotary encoder knob for volume control, and addressable RGB LEDs for underglow backlighting.

The Journey So Far

1. Fixing the Matrix Math

Since the Seeeduino XIAO doesn’t have a ton of GPIO pins, I couldn’t connect all 9 switches directly. Instead, I wired them into a 3x3 keyboard matrix. This lets me scan all 9 keys using just 6 pins, which leaves the remaining pins open to run the OLED display screen without running out of IO.

2. Adding Diodes

To make sure the keys register properly when pressed at the same time, I added a switching diode to every switch. They act like one-way valves to prevent ghosting when holding down multiple keys.

3. Hardware Add-ons

I’m adding three main features to the board:

Rotary Encoder (SW10): An infinite spinning knob that handles volume control by tracking internal switch pulses.
OLED Screen (J1): A tiny screen for animations that runs on I2C communication, meaning it only uses two lines (SDA and SCL) instead of a massive bundle of wires.
RGB LEDs: Daisy-chained NeoPixels that share a single data pin to control color and brightness individually.

Roadblocks & Lessons Learned

The Grid and Spaghetti Wire Mess: When I first started drawing connections in KiCad, it turned into a massive spiderweb of overlapping green lines. To make it worse, my grid settings were mismatched, so wires looked crooked and wouldn’t snap onto the component pins. I fixed it by resetting my grid snap, wiping the messy wires, and using Global Labels instead of drawing lines across the whole page. It looks way more professional now.
Diode Orientation: Placing 9 diodes in a tight grid got confusing, and I realized halfway through that I mixed up the direction on a few of them. If they face the wrong way, the switch breaks because current can’t flow back to the row pins. I had to look closely at the symbols and flip them so they all match.
Missing XIAO Footprint: KiCad’s Electrical Rules Checker threw an error because it couldn’t find a built-in footprint for the Seeeduino XIAO. After doing some research, I swapped it for a standard DIP-14 footprint. Since it shares the exact same 2.54mm pin spacing, the physical board will line up perfectly and the XIAO can slide right in.

What’s Next

Now that the schematic is done, I’m hitting ‘F8’ to pull all the components over into the 2D PCB editor canvas. Next up is the hard part: routing the physical copper lines without letting them cross each other!