Breadboard Buddy I2C for Adafruit components

Breadboard Buddy I2C for Adafruit components

Handy switches knobs and a display for microcontroller breadboard projects.

New V2 for Right Display

While developing some code to capture data from an inertial measurement unit I needed to take my knobs and switches outside to play but also needed to secure some expansion boards and wires.

I’m using a “Seeed Studio Expansion Board Base for XIAO” (should also be pin-compatible with Adafruit QT Py dev boards) and an Adafruit BNO055 for this project and decided to hang an “Adafruit Swirly Aluminum Mounting Grid” on the back to keep things together. (No, I’m not in the Adafruit marketing department 😊 ).

V2 is my “Lego®” compatible solution. The posts and holes are on standard Lego 8mm centers, 4.8mm diameter. 

There is a mount for x5 and x10 grids. 

2.1mm thru-holes are placed along the length of the mount matching the grid spacings so you can run a M2.5 tap through them then secure the grid with a few screws. 

Print the mounts ‘pegs-up’. Print the main body face down.

If you are splitting parts and doing multi-color, V2 includes new index marks around the knobs and numbers underneath the switches. 

Original V1 Description

I was tired of rigging up switches and encoders on a breadboard while developing microcontroller projects. Using up I/O pins, wires all over the place, accidentally knocking an encoder or switch loose while adjusting, ectara. It’s also handy writing to a display near the knobs/switches rather than looking away to a serial console/terminal to see what’s going on.

 Adafruit I2C Breakouts to the rescue!

4 wires (2 data wires, power and ground) de-cluttered my breadboard space and gave me lots of knobs to twist and buttons to push.

• Adafruit NeoKey 1x4 QT I2C Breakout: https://www.adafruit.com/product/4980
• Adafruit I2C Quad Rotary Encoder Breakout: https://www.adafruit.com/product/5752
• Adafruit Grayscale 1.5" 128x128 OLED Display: https://www.adafruit.com/product/4741
• 4 x Rotary Encoders: https://www.adafruit.com/product/377
• Kailh Mechanical Key Switches - Clicky White - 10 pack: https://www.adafruit.com/product/4955
• Translucent Keycaps for MX Compatible Switches - 10 pack: https://www.adafruit.com/product/4956

(Why not? Since there is a NeoPixel under each switch)

• 3 x 50 mm STEMMA QT / Qwiic JST SH 4-pin Cable: https://www.adafruit.com/product/4210

(If you don’t have connectors and a crimper in this size format. You might also want an additional longer one if you have a STEMMA QT connector on your microcontroller.)

With my continuing attempts to learn “Autodesk Fusion 360” I made this panel. It is more substantial than I first imagined because the force necessary to pushing down/activate the rotary encoder switches would bend the faceplate, legs, and flex the screwed down boards a bit. 

The screw holes are 2mm in diameter and are not threaded. I used 2-56 x ¼ inch round head machine screws from the local hardware store (approximately 2.1 X 6.3 mm). 

The switch standoff holes are 5.8MM deep and the display standoffs are 3mm deep. I’ve included a spacer.stl to prevent bottoming out in the display standoffs and marring the top surface. 

If you don’t have tiny flat-bottom taps, take whatever screw you choose, align it with the hole, push down firmly and turn your screwdriver to cut threads. Be careful not to screw in too far when cutting threads – 2mm is plenty, then remove the screws align the board(s), start the screws in your starter threads and tighten gently (in a crisscross pattern) until just snug.

The Rotary Breakout is secured with the shaft nuts.

Choose whether you want the display on the left or right and print the corresponding file. I originally designed this with the display on the left, but I really wanted it on the right after using it for a while.

I you have a multi-material printer you can choose ‘split object’ or ‘split to parts’ and pick a different color for the text objects.

Note: My slicer/MMU always prints in filament order, ie filament 1, filament 2, filament 3 … For best results load the text color sequentially before the main body color

I have included a simple test program “TestBoardBuddy.ino” that exercises the board components by displaying the encoder positions, encoder presses, and button presses. Remember to load the necessary libraries: Adafruit BusIO, Adafruit ST7735 and ST7789 Library, Adafruit GFX Library, Adafruit seesaw Library, and Adafruit SSD1327

Printing: 

I used Inland PLA+, 30% grid infill, and ‘Monotonic Lines’ for the first/bottom layer.