pdsink

Sink-only USB PD 3.2 stack for embedded systems: SPR + EPR, with a core free of platform and vendor dependencies.

<img src="./docs/images/intro1.jpg" width="40%">

This library focuses on the most common needs of PD‑powered projects and on ease of use.

Features:

• USB PD Rev 3.2 with SPR and EPR modes (sink side).
• Platform-agnostic C++ core.
• Reference implementation: FUSB302B + FreeRTOS.
• MIT license.

Not supported:

• Source role (SRC) and related modes (DRP/DFP/FRS/Alt).

Why

A lot of embedded designs only need one thing: to be a sink and behave correctly. In practice, available PD stacks usually come with at least one hard constraint:

• vendor lock-in / NDA / no public sources,
• tied to a specific OS or framework,
• incomplete sink-side feature coverage (e.g., no EPR support or poor spec compliance),
• difficult to extend to new TCPC/MCU combinations.

This library addresses these constraints through a sink-focused implementation and aims to improve adoption in modern embedded projects.

Project status

• Status: early stage; sink path validated on FUSB302B + FreeRTOS.
• Coverage: SPR/PPS/EPR sink negotiation validated on the current reference path.
• Seeking: validation on additional TCPC/MCU combinations.
• Real-world use: integrated into the Reflow Micro Table firmware (heater control path).

Usage

See the docs and examples.

• Current reference path: examples/fusb302_rtos_esp32c3_arduino (FreeRTOS, ESP32-C3, FUSB302).
• For a complex real-world scenario, see the heater-related classes in the Reflow Micro Table project.

When pdsink makes sense

This project can help when:

• you need dynamic power control at runtime (heaters, for example).
• you want to use an MCU with an embedded UCPD and simplify external components.
• you need “non-standard” voltages or current limits (via PPS/AVS profiles).

If you only need a single fixed profile, a simple PD trigger (e.g., CH224 or a similar external trigger) can be a more rational choice.

Project scope: sink role only. The non-goals in Not supported are intentional.

References

Other projects with USB PD support:

• Google Embedded Controller
• Zephyr Project
• USB Power Delivery for Arduino
• usb-pd

Documentation:

• USB Power Delivery