When working with USB-C Power Delivery, the CC (Configuration Channel) and VCONN pins are critical. They are used during negotiation to select the voltage and current profile that the charger provides. Without them, PD simply won’t work.

There’s a catch, though:

• A standard USB-C cable only forwards one of the two CC lines, depending on how the plug is inserted.
• The USB-C specification doesn’t require both CC pins to be passed through. That means if you just connect a charger through an ordinary cable, you can’t expose both CC/VCONN signals to your circuit.

For devices like my Power Meter and PD Logger, this is a problem. Both gadgets need to make the CC/VCONN lines available at their output port, so the downstream device can negotiate properly with the charger.

The solution: instead of relying on a regular cable, I mount a male USB-C plug directly on a small daughter PCB that connects straight into my circuit. This way, both CC/VCONN lines from the charger side are routed to the output connector. The result is full compliance with USB-C PD negotiation, regardless of plug orientation.

This small design choice turned out to be essential for making the tools reliable and universally compatible with different chargers.