Description

TinyPPS is a pocket-sized programmable power supply built on the USB Power Delivery (PD) standard and the USB Programmable Power Supply (PPS) feature. It transforms a standard USB-C PD charger into a flexible bench-style power source by negotiating selectable output voltages and current limits directly with the charger.

Key features:

• Support for fixed PDO and PPS profiles
• Operating VCC voltage range: 3 V to 31 V
• Fine-grained voltage adjustment via PPS negotiation (100mV steps)
• Output current up to 5 A (charger and cable dependent)
• Programmable current limiting (250mA steps)
• User-switchable output

Huge thank you to PCBWay for sponsoring this project!

Firmware

The firmware is written in C++ using the Raspberry Pi Pico SDK.

Flashing

There are two options to flash RP2040:

1. Via USB by pressing the BOOT button during power on. On a PC a new virtual drive called RPI-RP2 should appear. Then, drag and drop a .uf2 file onto the drive.
2. Via SWD interface by attaching a debugger like Raspberry Pi Debug Probe to the "DBG" connector and then using OpenOCD.

Hardware

Schematic and PCB are designed in KiCAD.

Key components:

• The schematic is based on the RP2040 and AP33772S reference designs.
• A 0.96 in 128×64 SSD1306 OLED is added to display the UI.
• A EC11 rotary encoder is added for user input.
• INA226 is used for measuring current and voltage. While AP33772s provides these features, INA226 gives more precise measurements.

Resources

1. Hardware design with RP2040
2. AP33772S I2C USB PD Sink Controller EVB User Guide
3. SSD1306
4. INA226
5. RobTillaart/INA226