emUSB-C PD

SEGGER emUSB-C PD is a compact USB-C Power Delivery protocol stack for embedded systems that need to negotiate power delivery over USB Type-C connections. The library implements the full PD protocol as defined by USB-IF, covering Source, Sink, and Dual Role Player (DRP) configurations. With dynamic power supply negotiation up to 20 V / 3 A, emUSB-C PD enables devices to request or provide optimal voltage and current levels, essential for battery-powered products, USB-C chargers, docking stations, and any embedded system that uses USB-C as a power interface.

Minimal Footprint, Flexible Configuration

The stack is architected in two layers: a device-independent protocol layer and a hardware-specific driver layer. Each layer is further divided into a base module (handling CC pin sensing and the application API) and a PD module (managing power delivery packet communication). This separation lets developers tailor the build to their use case, a sink-only configuration requires just 3.8 KB of ROM and 450 bytes of RAM, while the full Source + Sink + DRP stack fits in 5.1 KB of ROM.

Integration with the SEGGER USB Stack

emUSB-C PD can be used in combination with emUSB-Host and emUSB-Device for designs that carry both power and data over the same USB-C connector. It can also operate standalone, without any USB data stack, for devices that use USB-C purely as a power source or battery charging interface. Features include dead battery signalling, power role swapping, device detection and identification, and variable supply voltage negotiation. Written in ISO/ANSI C and delivered as source code, emUSB-C PD is portable across compilers and targets with royalty-free, one-time-payment licensing.

Core Capabilities

• Full role coverage: Source, Sink, and Dual Role Player (DRP) in a single codebase, so the same library serves a charger, a chargeable device, or a port that must negotiate either way
• Layered architecture: a device-independent protocol layer separated from the hardware-specific driver layer, and each layer split into a base module (CC pin sensing, application API) and a PD module (power delivery packet handling)
• Configurable build size: sink-only, source-only, and full Source+Sink+DRP builds let a project link in only the roles it needs
• Dead battery support: correctly handles the case where a device has no usable charge at power-on and must still negotiate an initial power contract
• Power role swapping: supports renegotiating which side of a connection sources power mid-session, relevant for docking stations and USB-C hubs

Typical Applications

emUSB-C PD is deployed in USB-C wall chargers and power banks that must advertise and negotiate multiple voltage/current profiles, in battery-powered instruments and industrial handhelds that need to both charge from and, in some cases, power accessories through a single USB-C port, and in docking stations and hubs that pass through power delivery negotiated between a laptop and an external charger. Because the stack is agnostic to whether emUSB-Device or emUSB-Host is present, the same emUSB-C PD codebase can be reused across a product line that ranges from power-only accessories to full USB data-and-power designs, reducing the engineering effort of maintaining separate PD implementations for each variant.