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You're both correct, but USB Power Delivery, like so many things USB, is a total mess with different revisions, and versions of those revisions, that each exten

You're both correct, but USB Power Delivery, like so many things USB, is a total mess with different revisions, and versions of those revisions, that each extend and deprecate parts of the previous revision. I'm going to ignore the actual protocol used for negotiation here, but there have also been at least three different protocols. The first revision, rev 1.0, had six fixed power profiles: 5V/2A, 12V/1.5A, 12V/3.0A, 12V/5.0A, 20V/3.0A and 20V/5.0A. These were deprecated by rev 2.0, version 1.2, which instead introduced power rules at four fixed voltages, supporting power supplies with different output powers. The maximum supported currents by the specification were 5V/3A, 9V/3A, 15V/3A and 20V/5A. These power rules were retroactively named the Standard Power Range (SPR) in rev 3.1. That revision also added the Extended Power Range (EPR), which raised all the current limits up to 5A, but only when used with electronically marked cables. EPR also added power rules at 28V, 36V and 48V, again requiring (differently) marked cables and up to 5A. So 5V/5A is a valid option, but only when used with a USB PD rev 3.1 compatible power supply and cable. Orthogonally to the fixed power rules, rev 3.0 introduced the Programmable Power Supply, which allows a configurable voltage between 3.3V and 21V in steps of 20 mV. This was extended by rev 3.1 with voltages between 15V and 48V in steps of 100 mV, called the Adjustable Voltage Supply. As far as I'm aware this is not commonly used, and most products advertising Power Delivery support use the predefined power rules.

reactordev 3y ago
The standard of evolving standard. Those looking take note, don’t rush to standardize something when the tech itself is still being tweaked and iterated on. Let it iterate, document it, but don’t put standards in place when you clearly can’t track or regulate it. You just look like that boomer who just now got their Windows 10 Upgrade CD to work. The reality is that with variable and programmable power supplies, it’s now up to the device to draw power at a balanced rate from the supply, instead of the “supply” pushing power in. Modern tech has allowed us to have supplies between 3V-48V, 500ma to 10A. All with a usbc head.
- wkat4242 3y ago
  Not standardising gave us the myriad of charging and headphone plugs on mobile phones in the late 90s/early 2000s.
- fecal_henge 3y ago
  Hate to be that guy but tweaking and iterating power delivery systems with no standards sounds like a way to get houses burned down.
Wowfunhappy 3y ago
I hate USB-C. What a mess. What good is a universal port if it's not actually universal? I would actually prefer different shapes, because then you could be pretty confident that if everything fit it was going to work. Like how USB used to be.
- simondotau 3y ago
  > What a mess. It’s such a mess that the EU took one look at it and said “let’s make that a universal standard and force it upon everyone!” Modern USB truly is the government bureaucracy of standards.
  - Guvante 3y ago
    EU has been trying to work with Apple on this almost since the lighting cable was released. I believe there were discussions about potentially standardizing on Lighting if Apple relinquished it's tight control over the technology but they were not interested in that path. The EU decided that Apple cannot dictate what cables are used to charge their phones to the degree of at one point charging manufacturers $4 per cable (to be fair it seems like Apple was providing the hardware so it wasn't a pure licensing charge).
    - simondotau 3y ago
      Huh? I didn't say anything about Apple. The parent post didn't say say anything about Apple. The grandparent didn't say anything about Apple. The great grandparent didn't say anything about Apple. The world doesn't revolve around Apple. My criticism of the EU policy has nothing to do with the port on an iPhone. If you're curious, my main objection to the EU is that I don't think USB-C is a good standard and I don't like the prospect of the whole industry stuck with USB-C longer than appropriate because there's no incentive to experiment and possibly come up with something dramatically better.
- Guvante 3y ago
  Is it really worse now than it was before? Having a plug on say a laptop that can be a charger, a HID, a drive, a monitor, or all of the above with a docking station is vastly superior to the old day IMHO. Unfortunately the cable to do that isn't cheap and is massively overkill for say a phone charger. Thus cable compatibility becomes a thing but looking at HDMI cable compatibility is always a thing. I think the problem is what used to be complaints about niche connectors are complaints about USB-C and it feels different and more impactful even if it isn't necessarily. After all I know back in the Mini-USB days you had manufacturers skipping the data pins to save some copper leading to frustration when you couldn't transfer files.

reactordev 3y ago

The standard of evolving standard. Those looking take note, don’t rush to standardize something when the tech itself is still being tweaked and iterated on. Let it iterate, document it, but don’t put standards in place when you clearly can’t track or regulate it. You just look like that boomer who just now got their Windows 10 Upgrade CD to work. The reality is that with variable and programmable power supplies, it’s now up to the device to draw power at a balanced rate from the supply, instead of the “supply” pushing power in. Modern tech has allowed us to have supplies between 3V-48V, 500ma to 10A. All with a usbc head.

wkat4242 3y ago
Not standardising gave us the myriad of charging and headphone plugs on mobile phones in the late 90s/early 2000s.
fecal_henge 3y ago
Hate to be that guy but tweaking and iterating power delivery systems with no standards sounds like a way to get houses burned down.

Wowfunhappy 3y ago

I hate USB-C. What a mess. What good is a universal port if it's not actually universal? I would actually prefer different shapes, because then you could be pretty confident that if everything fit it was going to work. Like how USB used to be.

simondotau 3y ago
> What a mess. It’s such a mess that the EU took one look at it and said “let’s make that a universal standard and force it upon everyone!” Modern USB truly is the government bureaucracy of standards.
- Guvante 3y ago
  EU has been trying to work with Apple on this almost since the lighting cable was released. I believe there were discussions about potentially standardizing on Lighting if Apple relinquished it's tight control over the technology but they were not interested in that path. The EU decided that Apple cannot dictate what cables are used to charge their phones to the degree of at one point charging manufacturers $4 per cable (to be fair it seems like Apple was providing the hardware so it wasn't a pure licensing charge).
  - simondotau 3y ago
    Huh? I didn't say anything about Apple. The parent post didn't say say anything about Apple. The grandparent didn't say anything about Apple. The great grandparent didn't say anything about Apple. The world doesn't revolve around Apple. My criticism of the EU policy has nothing to do with the port on an iPhone. If you're curious, my main objection to the EU is that I don't think USB-C is a good standard and I don't like the prospect of the whole industry stuck with USB-C longer than appropriate because there's no incentive to experiment and possibly come up with something dramatically better.
Guvante 3y ago
Is it really worse now than it was before? Having a plug on say a laptop that can be a charger, a HID, a drive, a monitor, or all of the above with a docking station is vastly superior to the old day IMHO. Unfortunately the cable to do that isn't cheap and is massively overkill for say a phone charger. Thus cable compatibility becomes a thing but looking at HDMI cable compatibility is always a thing. I think the problem is what used to be complaints about niche connectors are complaints about USB-C and it feels different and more impactful even if it isn't necessarily. After all I know back in the Mini-USB days you had manufacturers skipping the data pins to save some copper leading to frustration when you couldn't transfer files.