USB Type-C and Power Delivery Messaging

Figure 1: Power Delivery messaging comprises two types:
Control and Data

Continuing our review of USB Type-C and the associated Power Delivery 2.0 (PD) specification, let's now turn to PD message types. Whereas USB was originally conceived as primarily a serial-data interface with limited power-delivery capabilities, the proliferation of power-hungry mobile devices has forced a rethinking of that conception. With PD 2.0 came a much more flexible, and capable, power-delivery functionality for USB. PD messaging is a critical component in this regard.

USB Type-C Cable Detection

Figure 1: The four possible states of
connection for a USB Type-C cable

Having examined some of the basics regarding the USB Type-C connector and the Power Delivery 2.0 specification that complements the Type-C spec itself, we'll turn our attention to the topic of cable detection. The Type-C connector is reversible, which is to say there are four ways a cable can be connected between upstream- and downstream-facing ports (Figure 1). Not only that, but there are different types of Type-C cables. So how do the devices discern what's between them?