Checking USB Power Delivery with a Low-Cost Protocol Analyzer
1. Cypress Semiconductorâs CY4500 EZ-PD Protocol Analyzer has a pair of Type-C connectors that allow the analyzer to sit between a device and host.
I was going to do a round-up of USB Power Delivery equipment and test tools, but as this one’s just too fun, it gets its own article. Cypress Semiconductor’s CY4500 EZ-PD Protocol Analyzer (Fig. 1) handles USB Power Delivery control and power protocols. It acts as a Type-C pass-through, allowing it to monitor VBUS, VCONN, and USB-PD traffic. A third, MicroUSB connector connects to a host PC that runs a Windows application to control the analyzer.
Inside the small box is a Cypress Semiconductor PSoC (Fig. 2). It also has hooks into the power system and the handshake system that control how power is routed and controlled, as well as how alternate connections are managed as well.
The analyzer exposes the control signals (Fig. 3) just in case they are needed. Jumpers are included with the kit. Normally these are not needed.
Using the analyzer is extremely easy. Just plug it in and install the Windows-based EZ-PD Analyzer Utility application (Fig. 4). It is essentially a trace utility that captures every message, providing the details on the right side when a message is selected. Traces can be saved to a file.
The Configuration Channel (CC) line is the signal that handles the handshake for power management and data connection configuration. The utility operation is simple: Just start and stop recording. Basic filtering is provided, making it possible to easily locate error events or other actions.
The analyzer and software are not on par with the typical USB test equipment available, but these cost a lot more. They are also more useful in tracking down errors—especially timing- and power-related issues that this analyzer will not address. On the other hand, for less than $200 developers can track the protocols being employed over the cable and identify issues related to the protocols. This can be handy given the potential complexity of issues like USB Power Delivery power distribution.
For more information check out the CY 4500-EZ-PD site.
