Ah, yes, you are correct!
Then I don't know how to connect it without a USB-C split PD cable (which I don't have).
My setup is: a Mac Mini (with USB-C and USB3/2 ports) that I need to use as a host, and a PI as a device.
If I connect the upstream port to the host (Mac Mini), then I only have the USB-C PD connector on the hub, which I can connect to the Pi. But then, I can't connect the PSU to power the Pi (the USB-C on the Mac Mini doesn't provide the required power for the Pi), and even if the power were to be ok, the USB-C at the Pi will be in USB-C mode. If I use a Pi USB-C -> USB-2 plug -> USB-2/3 on the hub and USB-C upstream connected to the Mac Mini USB-C, the power via USB-C -> USB-2/3 will not power the Pi (correct?).
Without a full spec for your hub I can't really comment further. The USB C hubs with PD pass through that I have experience of do not have USB data lines on their power input port. They only have the pins required for PD.
PD is not actually required to run the Pi. It is required to run it with full current output to it's downstream USB devices*. USB 2 and USB 3 use separate pins in the connector so there is no such thing as USB 2 or USB 3 mode. In theory you could run a pure USB 3 and a USB 2 device from a single USB 3 host port.
According to the spec typical bare board draw for a Pi5 is 800mA.
IIRC, the spec for USB3 allows devices to draw up to 900mA without PD so a lightly loaded Pi5 with no USB devices downstream of it should be able to run from a USB 3 host port.
So, how to connect PI to the host (macMini with USB-C or USB-A ports) and also power the PI with the external PSU and set PI's USB-C to USB2 mode?
First, try a direct USB C to USB C or USB A to USB C connection. If your Mac Mini can function as a USB PD source it should default to 5V/3A via PD or whatever it defaults to on the normal USB +ve pin. USB A ports don't have PD so you get what you're given (likely 5v/900mA but that's a guess).
If you find you still need to inject external power to the Pi, get a USB A male to C male cable and modify it so that the +ve pins is disconnected or covered then power the Pi via its GPIO header. Or do what I do and use one of these: https://www.8086.net/products#80860016
*: Unless overridden in config.txt or the EEPROM config.
Statistics: Posted by thagrol — Mon Jul 29, 2024 3:10 pm