Dr. PD is a USB Power Delivery (USB-PD) power analyzer and programmable sink for engineers, hardware hackers, repair technicians, and anyone who wants to understand what happens between a USB Type-C power source and the device attached to it. Place it inline between a charger and a device, and Dr. PD captures the negotiation, measures voltage and current, and shows you exactly how power is being offered, requested, and delivered.

But Dr. PD is not just a passive observer—it can also act as a programmable USB Type-C sink, allowing you to request supported power profiles directly from compatible sources. That makes it useful both as a diagnostic instrument and as a practical lab tool for testing and characterizing chargers, cables, battery banks, docks, and USB-powered devices.

The Doctor Is In

USB power problems are often frustrating to diagnose. Flaky chargers, devices that charge slowly for no obvious reason, cables that work fine in one setup but not in another… there are so many failure points! Dr. PD gives you visibility into the conversation between a power source and a power sink, then correlates it with what is actually happening electrically. You can inspect how a source advertises its capabilities, how a device responds, when a power contract changes, and what happened right before a fault or fallback condition.

We designed Dr. PD to be useful even if you aren’t an expert in USB power negotiation. It logs and visualizes each message, providing a complete, human-readable breakdown of its contents and context. So, instead of relying on an oscilloscope or logic analyzer, you can watch a full USB-PD negotiation and correlate the messages exchanged by sink, source, and cables with changes in voltage and current. That is useful whether you are characterizing a power bank, investigating a charging problem, validating a third-party adapter, or just trying to understand why one configuration works and another one does not.

In addition to being a protocol analyzer, Dr. PD can also act as a USB-PD sink that supports modern high-power standards, including Extended Power Range, or EPR. When connected to a compatible source, this means that you’ll be able to draw up to 240 W (48 V at 5 A) directly from the banana jacks at the front of the device. You can request both fixed-voltage and adjustable-voltage charging modes (PPS and AVS) with resolution as low as 20 mV and 50 mA. That makes it perfect for characterizing the behavior of a charger or power bank, or for using USB Type-C power supplies as adjustable bench power sources.

Features & Specifications

Host connection: USB micro-B for power and data (~100mA when idle, up to 500 mA when active)
USB Type-C ports: 2 (one device under test, one for passthrough)
Banana jacks: 2 (for direct voltage and current measurement and sink operation)
Voltage and current ranges: Up to 60 V / 6A. Supports USB-PD 3.2, including Extended Power Range (EPR) up to 48 V / 5 A / 240 W
Signal outputs: Dedicated CC-line and Sync BNC connections for external monitoring and correlation with other instruments
Processor: Raspberry Pi RP2354A
Dimensions: 135 mm x 135mm x 50 mm (5.3 in x 5.3 in x 2 in)
Weight: 300 g (10.6 oz)

Analysis and Measurement

• Real-time capture and decoding of USB Type-C power negotiation traffic
• Virtually unlimited memory depth for message and VBUS capture, limited only by host storage capacity
• Search and filter message logs by content, type, sender, receiver, and other criteria
• Export captured data in standard formats for offline analysis and visualization, including CSV and JSON
• Realtime measurement of bus voltage and current
• Bidirectional VBUS monitoring to support dual-role power devices and port-independent connections
• Time-correlated views of communication and electrical behavior
• Stored charge and energy measurements over time to characterize battery capacity and charger performance
• Dedicated CC-line and VBUS outputs for external monitoring and correlation with other instruments
• Hardware sync output for external measurement correlation, such as with an oscilloscope, with complex trigger criteria based on message type, sender, receiver, transmission phase, and more

Programmable Sink Functions

• Operates as a programmable USB-PD 3.2 sink
• Supports both fixed-voltage and adjustable-voltage charging modes on compatible sources, up to 48 V, 5 A, and 240 W
• Supports both standard and extended power range (EPR) USB-C power sources
• Customizable voltage and current limits, including over-voltage and over-current protection thresholds

Software & Firmware

• Browser-based host software for control, visualization, and analysis runs on Chrome and is compatible with Windows, macOS, Linux, and Android
• The host software requires no special drivers or software installation, and runs entirely client-side, with no cloud dependencies, to keep your data private
• No accounts or subscriptions required; just open the software in a compatible browser and connect to your Dr. PD device
• A separate Python-based terminal application is available for users who prefer a command-line interface
• Fully programmable and controllable via SCPI over USBTMC, making it compatible with a wide range of existing test software and automation frameworks
• Python and JavaScript libraries included for direct control and integration into custom test scripts and environments
• Firmware upgradeable directly from the host software, with no special tools or programming hardware required
• The USB-PD stack is implemented entirely in firmware rather than relying on a dedicated USB-PD controller chip, making future upgrades easier

Open Source

Dr. PD is fully open source; our goal is to make the hardware, firmware, host software, and technical documentation available for everyone to inspect, learn from, improve, and build on. We will publish board schematics, firmware source code, host software, documentation, protocol notes, and a bill of materials under the GPLv3 license.

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