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I made a simple PCB that I wanted to be powered through a USB C connector with low current requirements (~50mA). I spent some time reading through the USB C Spec as well as reading other relevant questions on this forum and it seemed like the answer was pretty straightforward, I just needed each CC pin to be pulled to ground with a 5.1k resistor.

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This seemed to work with everything I tested at home. A source sees the CC line gets pulled down and activates the VBUS line. Many of my cables are actually USB A -> USB C so I guess in that case the VBUS is just active. BUT, a friend of mine has a cheap USB PD Adapter and it doesn't power my device. It charges my phone just fine, but not my device. Why would this be? From my understanding the PD aspect of it just means if the sink sends some commands over the CC lines the adapter will respond. But if my dumb device doesn't say anything it should just keep things at 5V by default?

Is this a matter of a cheap amazon part not following the spec properly, or am I misunderstanding things and doing something wrong?

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    \$\begingroup\$ You did everything right. It is the faulty adapter. If you a device has Type-C, it should provide the primary VBUS safe 5V if it senses the connect over CC pins. PD is optional. \$\endgroup\$ Jul 22, 2021 at 3:34

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