4 ms·

And the criticism is completely invalid here. The power spec is very clear and unambiguous, and there is only one way to get it right. It is not the fault of th

by teilo 7y ago

And the criticism is completely invalid here. The power spec is very clear and unambiguous, and there is only one way to get it right. It is not the fault of the spec when manufacturers cannot be bothered to produce a circuit that has already been designed for them in the spec itself.

TazeTSchnitzel 7y ago
The USB Power Delivery specification is very complicated and covers, despite the name, a lot more than power delivery.
- cesarb 7y ago
  But in this particular case, USB Power Delivery was not involved, only basic USB-C. The USB-C plug was designed so that simple uses, like the 15W charging RPi has, do not need USB Power Delivery at all, just a couple of identification resistors and a way to read the resulting voltage (which will tell whether you can use the full 3A or must use less).
silversconfused 7y ago
Too complex and overreaching is certainly a valid fault.
- oceanswave 7y ago
  If a spec defines a fully working part, and you go off and tackle the complexity by designing your own part that turns out to be non-compliant, then the blame is on the spec?
  - deleted 7y ago
    [deleted]
  - deleted 7y ago
    [deleted]
  - CriticalCathed 7y ago
    maybe the spec is onerous
    - CamperBob2 7y ago
      Or vague, or just plain incorrect. I could see making a mistake like this. The earlier USB specs called for goofy things like grounding the shield to the enclosure entrance via parallel RC networks instead of bonding it properly, as well as adding various bypass capacitors to the data lines(!). These guidelines were poorly thought out, widely misinterpreted and even more widely ignored. They have conditioned engineers to make their own judgment calls in areas where they really should have been both more descriptive and more prescriptive, so maybe this is one of those cases. I haven't looked at the post-USB 2 specs at all but wouldn't be surprised if they are nowhere near as clear, unambiguous, and well-thought-out as people here are saying.
  - silversconfused 7y ago
    Hey, it worked(?) for the web!
squeaky-clean 7y ago
The spec is not the product. The USB C spec is not a USB C charger. It may not be a valid criticism of the spec but it's a 100% valid criticism of USB-C
michaelt 7y ago
Blame for this problem is 80% on RPi, no doubt, but I'd say 20% of the problem is someone deciding to allow multiple cables, some with active components in them. If they'd instead specified that every detachable USB C cable must be 40 Gbps / 100 watt capable, and any lower-spec cable must be captive to the device (like mouse and keyboard cables are) then this problem wouldn't have happened.
- mmastrac 7y ago
  > If they'd instead specified that every detachable USB C cable must be 40 Gbps / 100 watt capable, and any lower-spec cable must be captive to the device (like mouse and keyboard cables are) then this problem wouldn't have happened. If you are specifying that every cable is going to be $30 minimum, then your spec is dead from day 0. The USB-C committee has to balance a spec that will be used by a significant chunk of the planet, not all of whom can afford expensive cables.
  - beatgammit 7y ago
    I like RJ-45 for this. I can choose between several different cables that are all compatible and pay only for the features/speed I need.
  - dingaling 7y ago
    Full-spec cables are only $30+ because that includes a premium margin for being full-spec, as a differentiator. If all USB-C detached cables had to meet full-spec then there would be price competition.
- monocasa 7y ago
  What happens with A to C converters and legacy cables? Or do we just not support A devices anymore?
adrianmonk 7y ago
It seems like the spec must be at least reasonably clear because after these mistakes are made, someone like Benson Leung can always point to it and the community has little trouble adjudicating that yes, the spec said this one thing, but someone did that other thing instead. Given this has happened time and time again, it seems like a process flaw more than a document flaw. Maybe well-meaning people just make mistakes. Or maybe people knowingly cut corners to save money (because saving on parts is a pressure that will never go away). Or something else. So some sort of process fix seems to be needed, one that will (1) reward those who succeed and/or (2) punish those who try to get away with violating the spec and/or (3) create tools (like test equipment or certification services or processes) to make compliance easier to achieve for those who are trying to. So, for example, could the Pi people have used some kind of device that would plug in and run through all the combinations? Or could there have been a canned list of test cases (representatives of different types of chargers, how they should behave) they should have run? Or could they have sent a prototype device off to USB Shouldn't Suck Labs to have them test it? Or email a schematic to them to have it reviewed by an engineer?
- smittywerben 7y ago
  > Given this has happened time and time again I wasn’t aware there were different specs until a few weeks ago. I’m sure the rpi4 was in development since last year. They should have tested more cables, maybe they can fix it somehow.
  - majewsky 7y ago
    > maybe they can fix it somehow Given the problem description (wrong number of resistors), I doubt that they'll be able to fix it in the existing boards. I don't know how feasible it is for them to retool, but maybe we'll see a model 4.1 with an additional resistor show up at some point.
Causality1 7y ago
I wish there was some kind of patent or trademark law that could be used to punish companies who advertise with the word "USB" or "Type-C" without adhering to the spec.
- CamperBob2 7y ago
  It is interesting that the USB Forum, for all their VID/PID douchebaggery, didn't register the trademark and enforce it on non-compliant implementations. That would have been right in line with demanding that everyone buy 65,536 IDs at a time for thousands of dollars while attempting to prohibit resale.
DuskStar 7y ago
> The power spec is very clear and unambiguous, and there is only one way to get it right. Obviously not, since there is a way to get it almost right, which is what the Pi 4 demonstrates here. Experience from cryptography suggests that for a spec to be truly unambiguous, any deviation should make the implementation fail obviously in as many situations as possible.

by teilo 7y ago

TazeTSchnitzel 7y ago

The USB Power Delivery specification is very complicated and covers, despite the name, a lot more than power delivery.

cesarb 7y ago
But in this particular case, USB Power Delivery was not involved, only basic USB-C. The USB-C plug was designed so that simple uses, like the 15W charging RPi has, do not need USB Power Delivery at all, just a couple of identification resistors and a way to read the resulting voltage (which will tell whether you can use the full 3A or must use less).

silversconfused 7y ago

Too complex and overreaching is certainly a valid fault.

oceanswave 7y ago
If a spec defines a fully working part, and you go off and tackle the complexity by designing your own part that turns out to be non-compliant, then the blame is on the spec?
- deleted 7y ago
  [deleted]
- deleted 7y ago
  [deleted]
- CriticalCathed 7y ago
  maybe the spec is onerous
  - CamperBob2 7y ago
    Or vague, or just plain incorrect. I could see making a mistake like this. The earlier USB specs called for goofy things like grounding the shield to the enclosure entrance via parallel RC networks instead of bonding it properly, as well as adding various bypass capacitors to the data lines(!). These guidelines were poorly thought out, widely misinterpreted and even more widely ignored. They have conditioned engineers to make their own judgment calls in areas where they really should have been both more descriptive and more prescriptive, so maybe this is one of those cases. I haven't looked at the post-USB 2 specs at all but wouldn't be surprised if they are nowhere near as clear, unambiguous, and well-thought-out as people here are saying.
- silversconfused 7y ago
  Hey, it worked(?) for the web!

squeaky-clean 7y ago

The spec is not the product. The USB C spec is not a USB C charger. It may not be a valid criticism of the spec but it's a 100% valid criticism of USB-C

michaelt 7y ago

Blame for this problem is 80% on RPi, no doubt, but I'd say 20% of the problem is someone deciding to allow multiple cables, some with active components in them. If they'd instead specified that every detachable USB C cable must be 40 Gbps / 100 watt capable, and any lower-spec cable must be captive to the device (like mouse and keyboard cables are) then this problem wouldn't have happened.

mmastrac 7y ago
> If they'd instead specified that every detachable USB C cable must be 40 Gbps / 100 watt capable, and any lower-spec cable must be captive to the device (like mouse and keyboard cables are) then this problem wouldn't have happened. If you are specifying that every cable is going to be $30 minimum, then your spec is dead from day 0. The USB-C committee has to balance a spec that will be used by a significant chunk of the planet, not all of whom can afford expensive cables.
- beatgammit 7y ago
  I like RJ-45 for this. I can choose between several different cables that are all compatible and pay only for the features/speed I need.
- dingaling 7y ago
  Full-spec cables are only $30+ because that includes a premium margin for being full-spec, as a differentiator. If all USB-C detached cables had to meet full-spec then there would be price competition.
monocasa 7y ago
What happens with A to C converters and legacy cables? Or do we just not support A devices anymore?

adrianmonk 7y ago

It seems like the spec must be at least reasonably clear because after these mistakes are made, someone like Benson Leung can always point to it and the community has little trouble adjudicating that yes, the spec said this one thing, but someone did that other thing instead. Given this has happened time and time again, it seems like a process flaw more than a document flaw. Maybe well-meaning people just make mistakes. Or maybe people knowingly cut corners to save money (because saving on parts is a pressure that will never go away). Or something else. So some sort of process fix seems to be needed, one that will (1) reward those who succeed and/or (2) punish those who try to get away with violating the spec and/or (3) create tools (like test equipment or certification services or processes) to make compliance easier to achieve for those who are trying to. So, for example, could the Pi people have used some kind of device that would plug in and run through all the combinations? Or could there have been a canned list of test cases (representatives of different types of chargers, how they should behave) they should have run? Or could they have sent a prototype device off to USB Shouldn't Suck Labs to have them test it? Or email a schematic to them to have it reviewed by an engineer?

smittywerben 7y ago
> Given this has happened time and time again I wasn’t aware there were different specs until a few weeks ago. I’m sure the rpi4 was in development since last year. They should have tested more cables, maybe they can fix it somehow.
- majewsky 7y ago
  > maybe they can fix it somehow Given the problem description (wrong number of resistors), I doubt that they'll be able to fix it in the existing boards. I don't know how feasible it is for them to retool, but maybe we'll see a model 4.1 with an additional resistor show up at some point.

Causality1 7y ago

I wish there was some kind of patent or trademark law that could be used to punish companies who advertise with the word "USB" or "Type-C" without adhering to the spec.

CamperBob2 7y ago
It is interesting that the USB Forum, for all their VID/PID douchebaggery, didn't register the trademark and enforce it on non-compliant implementations. That would have been right in line with demanding that everyone buy 65,536 IDs at a time for thousands of dollars while attempting to prohibit resale.

DuskStar 7y ago

> The power spec is very clear and unambiguous, and there is only one way to get it right. Obviously not, since there is a way to get it almost right, which is what the Pi 4 demonstrates here. Experience from cryptography suggests that for a spec to be truly unambiguous, any deviation should make the implementation fail obviously in as many situations as possible.