How to understand or differentiate between a USB upstream-facing port and a downstream-facing port?
Just want to understand it to place the resistors on the CCx pins in case of using a Type-C connector.
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1One way to learn the difference is to read the USB specification. It's freely availble, explains difference of UFP and DFP, including the resistors for Type-C connector CC pins. – Justme Mar 28 '23 at 19:24
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How to understand or differentiate between a USB upstream-facing port and a downstream-facing port?
At the very basic level, an upstream-facing port is a port on a device. Therefore the device port must have 5.1k resistors down to ground on both CC pins.
The "downstream-facing port" is a port on USB host, and a provider of power by default. It must have two pull-up resistors (or corresponding current sources) on each CC pin. The value of the resistors (56k,22k,10k) indicates the port power capability.
More details can be found here,
https://electronics.stackexchange.com/a/327946/117785 https://electronics.stackexchange.com/a/442152/117785 https://electronics.stackexchange.com/a/390723/117785
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