To answer all your questions:
Long form:
I want to use any of my externally powered USB Hubs, following the USB BC Standard, which is limited to 1.5 A. In theory you have to follow some resistor pull-down, -up, etc., but in the real-world the implementers don't follow that and deliver as much current as you pull. The USB standard promises a protective limiting, but in reality they behave more like a wall-socket, and may only shut down at much higher currents, seemingly more for self-protection, not for protection of the device. So, I would never trust any USB hub. LinusTechTips did a whole episode around USB (https://youtu.be/hiwaxlttWow), where they discussed that and other USB stuff.
I found also a professional measurement of different standard USB hubs, where they measured when the USB hubs actually started to limit their currents. It was multiple times beyond the official specification. Sadly, the document is now gone.
It seems these hubs are designed to output the max. power on all ports at once, but you can draw much more power on one port alone (without overheating, instability or whatever), if you don't have any other high-current devices in use at the same time.
Whatever: I don't want to challenge my luck, limit my current to be around 1.5 A, and have some power left over for the RP2040-Zero. Therefore the "high" 2 Ohm resistor R1, and not the ideal 1.2 Ohm. But, yes, rounding up to 2 Ohm is too much, I think using around 1.3 Ohm is better.
R1: See the first answer.
The diode: If I experiment a little bit, and use a regular LED, the resulting voltage and current could be much higher, and damage my RP2040, but w/ the diode I would be on the safe side.
Or do I miss something here?
TL;DR: I want to use any of my powered USB BC Hubs.How do you want to power the whole thing?
Long form:
I want to use any of my externally powered USB Hubs, following the USB BC Standard, which is limited to 1.5 A. In theory you have to follow some resistor pull-down, -up, etc., but in the real-world the implementers don't follow that and deliver as much current as you pull. The USB standard promises a protective limiting, but in reality they behave more like a wall-socket, and may only shut down at much higher currents, seemingly more for self-protection, not for protection of the device. So, I would never trust any USB hub. LinusTechTips did a whole episode around USB (https://youtu.be/hiwaxlttWow), where they discussed that and other USB stuff.
I found also a professional measurement of different standard USB hubs, where they measured when the USB hubs actually started to limit their currents. It was multiple times beyond the official specification. Sadly, the document is now gone.
It seems these hubs are designed to output the max. power on all ports at once, but you can draw much more power on one port alone (without overheating, instability or whatever), if you don't have any other high-current devices in use at the same time.
Whatever: I don't want to challenge my luck, limit my current to be around 1.5 A, and have some power left over for the RP2040-Zero. Therefore the "high" 2 Ohm resistor R1, and not the ideal 1.2 Ohm. But, yes, rounding up to 2 Ohm is too much, I think using around 1.3 Ohm is better.
To R2: I couldn't find any "real" datasheet on this, only the different pictures w/ instructions on AliExpress and eBay, so I want to play it safe, if you can give me a link to a real data sheet, this would be highly appreciated. But yes, I think I could lose R2.Er, what is the diode for?
And you still don't really need R1 or R2.
R1: See the first answer.
The diode: If I experiment a little bit, and use a regular LED, the resulting voltage and current could be much higher, and damage my RP2040, but w/ the diode I would be on the safe side.
Or do I miss something here?
Statistics: Posted by BlinkingStuff — Sun May 25, 2025 1:10 am