USB PD Protocol Support

USB Power Delivery (USB PD) is a protocol specification that enables flexible power negotiation over USB Type-C connections, supporting power levels up to 240W (48V at 5A) under the Extended Power Range specification. USB PD communication occurs over the CC (Configuration Channel) line of the USB Type-C connector using BMC (Biphase Mark Coding) signaling at 300 kbps. During a PD negotiation, the source advertises its power capabilities through Source_Capabilities messages containing Power Data Objects (PDOs), and the sink requests a specific voltage and current combination through Request messages. The protocol also handles role swaps, alternate mode entry (such as DisplayPort over USB-C), battery status, and firmware updates. USB PD is now essential in laptops, smartphones, monitors, docking stations, automotive chargers, and industrial equipment. Protocol analysis is critical for USB PD development because the negotiation sequence involves precise timing requirements, and failures can result in devices not charging, delivering incorrect voltages, or failing to enter alternate modes. Engineers must verify that PDO advertisements are correct, that power contracts are established within specification timing, and that error recovery mechanisms (hard reset, soft reset) function properly. Analyzing USB PD traffic requires decoding the BMC-encoded CC line signals into readable PD messages.