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Raspberry Pi admits to faulty USB-C design on the Pi 4

arstechnica.com

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Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#21

Post by BoorishBears »

jakeogh wrote: post #14
jhbhjjhvhjkgh wrote: post #7

Earlier quoted context omitted.

The whole USB-C PD spec is overly complicated but in this case these chips are to ensure that someone doesn't push 4a/19v over an improperly built USB-C cable - that can lead to fire and burns. Also, other cables may have chips in them for data negotiation, specifically TB3/PCI encapsulation (the data rate is so high that over 6 inches you start to run into issues).

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

How do you spec a fuse for out of spec usage? What's stopping me from connecting a strand of magnet wire between both sides?

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#22

Post by gambiting »

thijsvandien wrote: post #3

Reminder to self: being an early adopter sucks virtually always. Edit: Sure, the issue is rather easy to circumvent, but anyone would have preferred not to have it. At the very least, it affects the resale value. My point is that whenever the answer to the question 'do I need it absolutely right away?' is no, it's better to wait a bit, no matter how much you intend to buy it at some point.

I simply ordered one with the official power supply(at £8 it's cheaper than literally any branded USB-C charger) and would never even know there was an issue if not for the articles here.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#23

Post by kllrnohj »

jbarberu wrote: post #11

While this isn't great, as a consumer I don't really see too big of a problem. If I get a raspberry pi to use for home automation or as a media center, do I really need it to work with every USB-C cable? I'd think I'd just find one that works and let that be the dedicated raspberry 4 cable. If you're building a product based on Raspberry Pi that you're selling to others, then sure I could understand the outrage.

They chose to use a standard so yes it's a problem that they didn't follow it. It's pretty cut & dry here.

Fortunately in this case it fails to 0V so it's not a dangerous or damaging failure, but still the spec literally hands you a schematic. Is it that hard to just copy it? Why did they even try to be clever and use their own design in the first place just to save a single 5.1k ohm resistor?

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#24

Post by TeMPOraL »

gambiting wrote: post #22
thijsvandien wrote: post #3

Reminder to self: being an early adopter sucks virtually always. Edit: Sure, the issue is rather easy to circumvent, but anyone would have preferred not to have it. At the very least, it affects the resale value. My point is that whenever the answer to the question 'do I need it absolutely right away?' is no, it's better to wait a bit, no matter how much you intend to buy it at some point.

I simply ordered one with the official power supply(at £8 it's cheaper than literally any branded USB-C charger) and would never even know there was an issue if not for the articles here.

Same here. For that price, anything else I could get would probably turn out to be a half-broken counterfeit garbage that might burn my house down. I'm considering buying an additional charger from them just to have a spare for my other USB-C devices.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#25

Post by wlesieutre »

jakeogh wrote: post #14
jhbhjjhvhjkgh wrote: post #7

Earlier quoted context omitted.

The whole USB-C PD spec is overly complicated but in this case these chips are to ensure that someone doesn't push 4a/19v over an improperly built USB-C cable - that can lead to fire and burns. Also, other cables may have chips in them for data negotiation, specifically TB3/PCI encapsulation (the data rate is so high that over 6 inches you start to run into issues).

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

You can plug a 5 amp rated extension cord into a residential plug on a 15A breaker and the breaker won’t protect you from overloading the cable with 15A. So yes, those sorts of light duty cables have their own fuse to prevent this.

But I really would not trust all the no-name vendors flooding the market with shitty USB cables to include correct safety measures in all of their cables, so requiring cables to specifically request higher power levels seems like a better precaution to rely on in this case.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#26

Post by jakeogh »

BoorishBears wrote: post #21
jakeogh wrote: post #14

Earlier quoted context omitted.

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

How do you spec a fuse for out of spec usage? What's stopping me from connecting a strand of magnet wire between both sides?

A consumer does not solder USB connectors together with magnet wire.

Power plug compatibility which relies on software for fire safety is a bad idea.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#28

Post by SSilver2k2 »

solarkraft wrote: post #18

How hard is it to to copy a [expletive] schematic? Edit: I'm serious. What convinced them to implement a design different from the example in the spec that simply does not work (hello, testing?)?

The USB-C spec is 300 pages with multiple errata and revisions. It's not just one schematic.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#29

Post by tjohns »

jakeogh wrote: post #14
jhbhjjhvhjkgh wrote: post #7

Earlier quoted context omitted.

The whole USB-C PD spec is overly complicated but in this case these chips are to ensure that someone doesn't push 4a/19v over an improperly built USB-C cable - that can lead to fire and burns. Also, other cables may have chips in them for data negotiation, specifically TB3/PCI encapsulation (the data rate is so high that over 6 inches you start to run into issues).

So, the spec allows an under-gauged cable to be plugged into a power outlet, and then relies on software (instead of a fuse) to not start a fire. I'm looking for a word... worse than awful...

(a) A fuse only prevents over-current based on the port's rating, not the cable's. It wouldn't help here.

(b) USB-C has several modes of operation. The thinner cables aren't under-speced in the lower-tier modes. They're perfectly fine for powering a mouse or carrying low-speed (USB 2.0 class) data. But not for charging a laptop, or other high current / data-rate uses.

Re: Raspberry Pi admits to faulty USB-C design on the Pi 4

#30

Post by tjohns »

baq wrote: post #10
fit2rule wrote: post #5

Damn, did they just Osborne themselves? I for sure have decided to hold off on a Pi-4 until this issue is fixed, since its really a hassle. Maybe a smarter move would've been to bundle the Pi-4 charge (non E-cable) to avoid dissatisfaction with this mis-design ..

They provide their own charger. It works, I’ve got one.

Yes, but it's an extra expense. If you've got spare USB-C chargers you could use, it's tempting to wait.
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