Oh god I just read about the RPi 5 power supply situation. It's so dumb.
From https://www.raspberrypi.com/news/the-inside-story-on-the-new-raspberry-pi-5-hackspace-72/ : RPi 5 needs > 15W in some situations, but they didn't want to put DC-DC converters on the board to use 9V/12V USB-PD modes.
So instead it looks like they have a hacky non-standard 5V/5A mode which only works with their own power supply?!
What the fuck.
@delroth And seems to be not just non-standard as uncommon, but actually not following the USB-C and Power Delivery standards (assuming my quick skim is correct)... and considering you need better cables for normal 5A USB-PD this is going to be "fun"...
@simonlbn @delroth The USB-PD spec supports a maximum of 5A at all voltages, but most implementations top out at 3A at 5V because apparently nobody is going to want 5V at 5A, right?
Pretty sure they’re not violating the spec - it’s more that a lot of chargers violate the spec by making assumptions. Given the ferocious heat budgeting that must go on in RPi design and the fact that buck/boost converters will always generate heat (and the higher the current, the more heat) I can understand not wanting to do that on the board.
@m @simonlbn @delroth You're wrong. The spec explicitly states that the maximum current at 5V is 3A. Anything above is clearly non-standard. You can get up to 5A with PD, but only at or above 20V and with a properly advertised e-marked cable.
A device that requires 5A at 5V is non-compliant and can't be said to be USB-PD compatible, period. Most cables aren't rated for such current either.
@dos @m @simonlbn @delroth You can do 5A at lower voltages using PPS. I don't know if that's what RPi is doing though.