[marcosdumay]

At this point I'm even surprised that compliant cables and chargers exist so the GP can have that problem.

But I believe the specs are that way to avoid problems with OTG devices. If both devices decide to just push a voltage into the cable at the same time, you risk spending a great deal of energy or even start a fire. That said, there are better ways to deal with this issue; those are just slightly more expensive.

[sidewndr46]

I think the Apple USB-C charger I have is compliant and so is the cable. I actually use it to charge my Samsung phone primarily, but inadvertently discovered that it won't run a Raspberry Pi 4 at all. The $12 adapter that is sold for that purpose runs the Raspberry Pi 4 just fine. Apparently because it just supplies 5 volts all the time, no matter what the device says.

[lxgr]

The Raspberry Pi 4 has a design error in its USB-C circuitry.

It does include a pull-down resistor, but wired incorrectly (compliant devices need two), which results in compliant chargers only correctly detecting it when using a “dumb” (i.e. containing no e-marker chip) USB-C-to-C cable. Your Apple cable probably has a marker (all their Macbook charging cables have one, for example).

[sidewndr46]

Thanks for the explanation. I actually found out the USB-C plug can act as a USB device. At USB 2.0 speeds oddly enough. So I have all my Pi 4s configured now in that mode and I just power them through the 5 volt header, which seems simpler. Albeit less convenient.

I had to get this USB "power blocker" that only passes the data pins through, otherwise the Pi runs off the computer it is plugged into all the time

[lxgr]

> At USB 2.0 speeds oddly enough.

That's because USB 3 is not natively provided by the SoC on the RPi 4, but rather by a dedicated IC, connected to the main SoC via PCIe :)

Hence there's two USB 3 ports and two USB 2 ports, but wired completely differently internally! Presumably the USB-C port is connected to the SoC more directly.

[somat]

If it is all 5 volts, it will not do much. But perhaps that screwball PD stuff would get you in trouble. The OTG stuff, just concerns who is the usb host. Where the otg cable instructs a normally client device to act as a usb host, Where the holy grail was to find that magical OTG cable that would let me charge the phone while it was acting as host. Hmmm... on reflection, this would be any dock right?

And a rant, for free: Holy smokes, I think OTG may be the second most braindead marketing dribble sort of acronym to come out of tech, right behind wifi(wireless... fidelity? what does that even mean?)

[lxgr]

Maybe the USB-IF agrees, because OTG is no longer a thing with USB-C.