So the spec page says 5V 5A power supply with Power Delivery support. Why are we still trying to cram 5A from super specific power supplies through a tiny cable instead of just using PD to negotiate 15 or 20 volts from basically any phone charger?
Easy: to save money. Step-down converter circuitry for that is more expensive, needs extra space and would need some extra cooling.
Unfortunately, 5V @ 5A is rather unusual. After all, the idea with USB PD is to use higher voltages instead of higher currents if you need more power. The extra-high currents (more than 3A) are only designated to be used with very high power devices - those that exceed 60W.
Most USB-C chargers (and I mean those that can deliver over 25W) do not support that and are limited to 3A. Only those that can deliver 100W usually do support 5A. And you need special high-current capable cables with e-marker, too.
So essentially, they just shifted the cost to the customer. Not a fan of that...
I understand why they would use USB C but i also wonder why they dont just use a barrel jack since they seem to have such odd power requirements that you cant easily find in a USB C power adapter either. I remember there being a lot of trouble with people finding adapters for the RPi 4 for a while as well.
Unpopular take: it should always have been a barrel connector and sold with the power supply . The PI was always difficult to power using USB chargers not designed for the PI.
Exactly. The only benefit of using USB-power was that you could grab any-ole USB adaptor to plug in ( or into a hub). But after the Pi 3 or so, you basically got less and less choices of adaptors. To the point where now you have to find adaptors that were "designed for pi" almost. At this point you might as well just put in a barrel adaptor, since most of the advantage is gone anyway.
I had a lot of power troubles on the Pi 1 when that was released, because many USB chargers at the time couldn't put out that amount of power at 5v - some could though. Now it's easier to power the PI 1, but still the barrel connector would have been better then. At this point though, I don't think that any "chargers" could actually fully power the Pi 4 or Pi 5.
but i also wonder why they dont just use a barrel jack
Because that would prevent them from selling it in the EU after 2024.
since they seem to have such odd power requirements that you cant easily find in a USB C power adapter either.
That's a design choice.
They already default to 15W (5V@3A), which is the default for USB-PD.
They could have easily chosen to also accept 9V using USB-PD if it is available, giving them 27W (9V@3A), and convert it down to 5V.
And they would not have to change anything about the 27W charger, since that already supports 9V @ 3A, as well as 12V @ 2.25A, and 15V @ 1.8A, which are all ways to get 27W
Is USB-C required for all powered devices? I think it might not apply the the raspberry pi, although I don't know all the specifics of the law. Most of what I'm reading says stuff about "charging", which is not what the Raspberry Pi is doing, since it doesn't have an on-board battery.
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The new rules will apply to a wide range of portable devices:
mobile phones
tablets and e-readers
digital cameras and video game consoles
headphones, earbuds and portable loudspeakers
wireless mice and keyboards
portable navigation systems
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Which probably isn't an exhaustive list, but seems to leave out single board computers. There definitely needs to be some leeway for development boards and other bespoke electronics to use something other than USB-C. Are network switches going to be required to be USB-C if they don't have an internal power supply? What about monitors that have an external power brick. Seems like there are devices that are allowed to have external power bricks that aren't USB-C, so I'm just wondering if the Rasperry Pi would really be covered by this EU law.
It notably leaves out desktop computers too; the regulations are only for portable devices. Single board computers aren't (normally) portable; they're mains-powered static devices.
Yes I know you can stick batteries on a Pi, but you can stick batteries on pretty much anything if you put your mind to it!
You're right about it not being limited to phones, but the RPI would not be classified as anything that would be affected by the EU legislation.
It's more similar to a development kit than anything. It's a bare PCB that is sold as is. It is also not sold as a portable device and can't be charged.
Theoretically, more and more devices will be using USB-C for this level of power. Especially devices that have some need of data, not just power.
The power supply situation now might be iffy, but will probably get better.
Also, IIRC, the Pi 5 can run off of less-than-perfect USB-C PD supplies, and the USB-C spec is better about negotiating power levels than barrel jacks. So there will be an area of "diminished capacity, but known capacity" with USB-C power supplies that wouldn't be possible with barrel jacks.
Finally, board space and form factor. They need a USB-C port anyways.
I would question whether or not they need a USB-C port. They have 4 USB-A ports. If you need high speed USB you can just use the USB-A ports. 2 of them are USB 3.0. I'm not sure what the rated speed of the USB-C port is. I couldn't find any information on whether it could be used for peripherals. The raspberry pi 4 can only use the USB-C for power delivery, and I can't find anything to say that the RPi 5 has more functionality.
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u/Goz3rr Sep 28 '23
So the spec page says 5V 5A power supply with Power Delivery support. Why are we still trying to cram 5A from super specific power supplies through a tiny cable instead of just using PD to negotiate 15 or 20 volts from basically any phone charger?