Purpose

While I’m well aware USB-PD→DC cables exist, these are preset to a specific voltage. Using the same USB-PD with different devices needing different voltages means unplugging and plugging in a different cable each time. There has to be a better solution, and thanks to Adafruit, we can make it! This design uses 4 LED lit push button switches, and a 0.91 inch OLED screen, to choose from 5v (default), 9v, 12v, and 20v. When first turned on, 5v is chosen by default.

Usage

The unit requires the following power inputs:

5v to Arduino	Ensure the Arduino receieves a consistent power output and preserve all available current through USB-PD is available for any devices you have connected.
USB-PD	The main power input. Please ensure your USB-PD power supply supports all of the voltages you plan to use.

Pressing a specific voltage pushbutton results in that switch lighting up and the OLED screen displaying the currently operating voltage. If the selected voltage cannot be set, either due to a communications error or the USB-PD power source not supporting that voltage, an error will be displayed and the previously working voltage left enabled.

Status

This is a work in progress, expect updates to be posted as time/testing permits

Done

• Component List

• Pin count confirmation

• Arduino microcontroller restrictions confirmed

• Parts ordering

• Pinout and wiring confirmation

• Switch/LED/OLED screen code validation in simulation

To Do

• Design 3D model for case

  • Split into Top and Bottom for easy printing

• Connect Arduino, Switches, LEDs, and OLED to confirm code functionality with hardware

• Connect HUSB238 and confirm initialization/response

  • Confirm continued functionality with OLED

• Connect USB-PD source

  • Confirm each voltage change occures

  • Measure output with volt meter

• Finalize and publish

Components

Quantity	Name	Purpose	Link
1	Adafruit USB Type C Power Delivery (HUSB238)	Does USB-PD heavy lifting and supports I2C control for "on the fly" voltage changes.	https://www.adafruit.com/product/5807
1	Adafruit Monochrome 0.91 inch Display (OLED)	Provides a feedback mechanism to the user to confirm if the chosen voltage was changed successfully or if the USB-PD power source does not support that voltage.	https://www.adafruit.com/product/4440
4	Adafruit 16mm Illuminated Push Button Momentary	Used to choose which voltage you want.	https://www.adafruit.com/product/1440
1	ATmega328P based Arduino	The control brains. Contains the code to control the USB-PD board and OLED screen.	Favorite component source
4	10k Ohm Resistors	Pulldown resistor for each switch.	Favorite component source
1	330 Ohm Resistor	Current limiting resistor for LEDs for indicating currently enabled voltage.	Favorite component source

Wiring Diagram

For those who want a more checklist type wiring list, here is the table of Arduino Pins to component pins/pads, if there is an inline resistor, and a handy extra space to mark off when you’ve completed that connection.

Ardunio Uno Pin	Inline Resistor Value	Component Pin/Pad	Done?
Ground	330 Ohm	Cathode (negative) of each LED. All LEDs can be tied together and linked to one resistor
Ground	10K Ohm	Pin 1 of "5v" Switch
Ground	10K Ohm	Pin 1 of "9v" Switch
Ground	10K Ohm	Pin 1 of "12v" Switch
Ground	10K Ohm	Pin 1 of "20v" Switch
5v (Vcc on some Arduino models)		Pin 2 of each Switch, VIN on OLED, V+ on HUSB238
2		Pin 1 of "5v" Switch
3		Pin 1 of "9v" Switch
4		Pin 1 of "12v" Switch
5		Pin 1 of "20v" Switch
9		Anode (positive) of "20v" indicator LED
10		Anode (positive) of "12v" indicator LED
11		Anode (positive) of "9v" indicator LED
12		Anode (positive) of "5v" indicator LED
A4		SDA pins on OLED and HUSB238
A5		SCL pins on OLED and HUSB238

For those who are more visually oriented, here is a Fritzing wiring diagram: