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USB Power Delivery: Plugging into the Benefits

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Re: USB Power Delivery: Plugging into the Benefits

#111

Post by mtabini »

userbinator wrote: post #92

IMHO this is a classic example of extreme overcomplexity leading to fragility and regulatory capture along with increased opportunities for antiuser hostility. Practically all devices needed nothing more than +/- on a robust barrel jack, but now we have negotiable voltage (with disasterous consequences if there is a bug in the inherently software-driven process --- which will certainly happen) pushing insane amounts…

Can I offer a counterpoint? Much like OG USB put a 5V supply within everyone's reach, USB-PD has made programmable, higher power supplies available to everyone. That's a big deal, because PSUs are an expensive portion of a product, especially for small manufacturers and hobbyists. Having a dedicated standard that supports multiple voltages and currents allows small players to take advantage of the same economies of scale as the largest electronics manufacturers.

Case in point, IKEA will happily sell you a very well built 20W power supply that provides 5, 9, 12, or 15V for less than $5 here in Canada, and you can get a similar price from legitimate Asian distributors, even when buying in limited quantities. If you're working on a small-batch electronic product, that's a boon to your BOM; if you had to go out and source a dedicated barrel-jack PSU with the same capabilities, it'd cost much more, and you don't know what kind of quality you'd be getting.

Where the standard really falls on its face, IMO, is in its opacity. You can get a chip that does the PD negotiation for pennies, but there is no way to inspect the protocol without shelling out thousands for a dedicated analyzer, so when things don't work, it's really hard to troubleshoot the reason.

(Disclaimer: I'm working on an open-source protocol analyzer, so this probably colours my view on the matter a little.)

Re: USB Power Delivery: Plugging into the Benefits

#112

Post by Havoc »

smallmancontrov wrote: post #12

Speaking of which, does anyone know a line of PD Decoy modules to convert barrel jacks to USB-C without the atrocious behavior of "oh, the charger doesn't have 12V, here's 9V have fun!" that the early ones all did? Ideally I'd like a little red light to come on or something, but I'd settle for not silently browning out the device.

Don’t think you’ll find it cause it’s not an issue with the decoy - that’s the expected behaviour. 12v isn’t mandatory. Which is insane but here we are.

On the plus side some of the bottom tier anker chargers will do 12v.

Plus I think the very new PPS ones should too

Re: USB Power Delivery: Plugging into the Benefits

#113

Post by ranger207 »

chocolatkey wrote: post #75
ranger207 wrote: post #55

Earlier quoted context omitted.

I have a couple like that in my mini rack. The problem is the power supply: these take 65W, so I figured I could get a quality 140W charger and power them both, but it turns out that things like "unplugging something else" would kill their power. I had to spend a lot more on a StarTech charger to get the performance I needed

Which startech product did you end up getting? One of the hubs or chargers? I have a similar issue with various USB-C rack devices

This charger: https://www.startech.com/en-us/computer-parts/424dna-usb-c-c...

Re: USB Power Delivery: Plugging into the Benefits

#114

Post by megous »

mschuster91 wrote: post #42
exmadscientist wrote: post #26

Earlier quoted context omitted.

That's how it's supposed to work, yeah. But there is some trash out there in the world. A lot of it, actually. Some naughty cables work with some naughty chargers work with some naughty devices. Postel's Law in action, I guess? Usually the best place to fix it is by getting rid of the bad cables. Usually.

> Usually the best place to fix it is by getting rid of the bad cables. Usually. No. There is no USB-C to C cable that will charge a badly implemented device with a standards compliant charger. That is the entire point. An USB A to C cable is completely standards-compliant and safe, even if it always supplies 5V on the C end - any standards compliant USB-C device should not activate the MOSFET on its Vbus line unless…

You may wish to re-read the type-c specification, especially 4.5.2.2.3.2:

"A USB 2.0 only Sink that doesn’t support accessories and is self-powered or requires only default power and does not support USB PD may transition directly to Attached.SNK when V BUS is detected."

or 4.5.2.2.5:

"A port that entered this state directly from Unattached.SNK due to detecting V BUS shall not determine orientation or availability of higher than Default USB Power and shall not use USB PD."

or 4.5.2.2.11.2:

"The port shall transition to Attached.SNK after tCCDebounce if or when V BUS is detected."

CC detection, let alone PD negotiation is not needed. You can draw up to 2.5W right away from Vbus and be standard compliant without wiring anything to CC signals.

Of course if you try this with a DRP device like a smartphone, you'll get no power. But that's not really an issue for type-c chargers or USB A-C cable assemblies.

Re: USB Power Delivery: Plugging into the Benefits

#115

Post by megous »

seba_dos1 wrote: post #79
megous wrote: post #78

Earlier quoted context omitted.

It's certainly not easier. Type-c power sink can advertise USB default, 1.5A or 3A easily. USB default is not necessarily underpowered. You still have to use BC1.2 to see if the source is actually underpowered. If you're just a microUSB device, you'll also check based on BC1.2. And you can ignore CC/Rp check. It's actually simpler. I guess you can assume anything advertising itself as USB default is underpowered, but…

It sure is. You can just spec it to require a USB-C 7.5W/15W source and then you can gate the operation behind a simple analog circuit and Bob's your uncle. No such way with microUSB until you implement BC1.2, which you don't have to support with USB-C (though it's certainly nice when you do). > but then you'd be wrong Not at all, it would just miss signaling it's not compatible with, just like with all sorts of prop…

Yes, that way your type-c device will also be refusing to work with many sources that can provide enough power, that is with anything advertising USB default power.

For proper detection of actually underpowered source without awful lot of false negative results, you always need BC1.2. You're just adding type-c CC pins circuitry on top maybe to detect what power is availabe in non-default-usb-power scenarios. If you just use CC pins for detection, a lot of your users will not like you, and will not understand why they can't charge your type-c port featuring smartphone or whatever with a perfectly capable 2.1A/5V charger connected via USB A-C cable.

Been there done that.

Re: USB Power Delivery: Plugging into the Benefits

#116

Post by mschuster91 »

exmadscientist wrote: post #13
hazkoulia wrote: post #4

I'm looking forward to USB-C PD small format factor PC's. A decent amount of room in the PC cases is taken up by the power supply. And if USB-C could somehow provide a range of voltages to the motherboard, SFFPC's could be downsized even more

> And if USB-C could somehow provide a range of voltages to the motherboard, SFFPC's could be downsized even more You reeeeeeally don't want to do that. Cable inductance is a big deal, among other issues. You want the main DC-DC regulators on the board, usually right at the load, for the main loads. Most of the PSU bulk is for dealing with mains itself: handling 50/60Hz or mains isolation is just physically large. Ge…

> I can't even begin to comprehend the horrors of a USB-PD negotiation involving multiple voltages. It's already the worst standard I've ever had to deal with.

Yeah but usually you don't have to deal with that yourself but have some sort of chipset that handles all the USB-C PD and, optionally, even data-lane muxing stuff.

Re: USB Power Delivery: Plugging into the Benefits

#117

Post by seba_dos1 »

megous wrote: post #115
seba_dos1 wrote: post #79

Earlier quoted context omitted.

It sure is. You can just spec it to require a USB-C 7.5W/15W source and then you can gate the operation behind a simple analog circuit and Bob's your uncle. No such way with microUSB until you implement BC1.2, which you don't have to support with USB-C (though it's certainly nice when you do). > but then you'd be wrong Not at all, it would just miss signaling it's not compatible with, just like with all sorts of prop…

Yes, that way your type-c device will also be refusing to work with many sources that can provide enough power, that is with anything advertising USB default power. For proper detection of actually underpowered source without awful lot of false negative results, you always need BC1.2. You're just adding type-c CC pins circuitry on top maybe to detect what power is availabe in non-default-usb-power scenarios. If you j…

Yes, that's all true. It's also irrelevant, as USB-C devices aren't required to support BC1.2, and the same concern applies to any proprietary signaling method you won't handle. "This thing requires 15W USB-C power source" is easily understood, regardless of existence of >=15W USB-A power bricks using QC3.0 or whatever else.

Supporting BC1.2 in a smartphone won't make it any more complex than it already is (been there done that). We're talking about simple equipment here, where handling USB-C power correctly can be easily done without any ICs.

Re: USB Power Delivery: Plugging into the Benefits

#118

Post by anon7000 »

userbinator wrote: post #98
mmastrac wrote: post #93

Earlier quoted context omitted.

The consequences of plugging the wrong voltage or polarity into a barrel jack, most of which are compatible enough, is pretty bad. Ask me how I know.

That's still far simpler and more obvious than the insanity of USB-C. Looking at all the complaints about "noncompliance" makes it much clearer.

Is it? DC barrel plugs look identical to most users. Just like USB C. Only one of them negotiates the correct voltage by default in most cases.

This is a non issue, IMO. Does it depend on the electronics being designed correctly? Sure, but that’s the case for all electronics, and most devices probably build on some widely-available standardized control boards from 3rd parties.

As a user, I’m sooo happy that I can bring a portable battery and a wall charger, and both can recharge every single one of my portable devices. From gaming handhelds to large, powerful laptops, to wireless earbuds, to cameras, to smart watches, to flashlights. All with very different power requirements.

Re: USB Power Delivery: Plugging into the Benefits

#119

Post by rpaddock »

I have found this ST Discovery kit extremely useful in figuring out what my USB-C power sources could actually supply.

"The STM32G071B-DISCO Discovery board is a demonstration and development platform for the STMicroelectronics Arm® Cortex®-M0+ core-based STM32G071RB microcontroller and particularly the USB Type-C™ and Power Delivery controllers.

...

The STM32G071B-DISCO Discovery board discovers and displays USB Type-C™ port capabilities such as data role, power role, VBUS and IBUS monitoring. ..."

https://www.st.com/resource/en/user_manual/dm00496511-stm32g...

Around ~$70 US now. Was around $50 when I bought mine a couple of years ago.

STM32G071B-DISCO at Mouser or Digikey.

Re: USB Power Delivery: Plugging into the Benefits

#120

Post by throwaway81523 »

Madness. USB C doesn't even let you control which way the power goes. Try to charge your phone by plugging in a USBC power bank? Oops, the phone is charging the power bank instead of the other way around. Sometimes you can't even make that stop without a USB-A cable. I can't imagine what kind of fools invented that.
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