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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

#91

Post by Florin_Andrei »

groovybits wrote: post #33

From a Pi consumer perspective, this is not that big of a deal. However, it damages the purpose (in name) of USB C. Isn't C supposed to be the 'all purpose' spec? If we have popular manufacturers failing to follow the spec, we end up with cables marked as 'compatible with Raspberry Pi' or 'compatible with Nintendo Switch'. To the average consumer (and even most techies), USB C was supposed to be the 'one size fits al…

> From a Pi consumer perspective, this is not that big of a deal.

Well, didn't seem that way to me when I bought an RPi4, tried it with two different power supplies and cables, and it didn't work at all. I thought the device was DoA so I did an RME with the distributor.

Today I learned a different story, and now I'll have to scrounge up yet another cable to see what the true story is. The one cable I have not tried may or may not be "dumb" enough for the RPi4 to work.

It's annoying at best.

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

#92

Post by KineticLensman »

johnhenry wrote: post #64
ChuckMcM wrote: post #57

Earlier quoted context omitted.

There is an old joke about the American West which goes, "Q: How do you know which people were pioneers? A: They are the ones with arrows in their back." USB-C is a phenomenally complex system from an engineering perspective, serving at least three masters (compatibility, power delivery, and enhanced performance). As these systems go through the standards process you have vendors designing silicon in anticipation and…

Wouldn't true pioneers have arrows in their front?

In the UK House of Parliament the two main parties sit in rows and face each other across the house. It's said that the politicians on the front bench (the party leaders) have their opponents in front of them and their enemies behind.

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

#93

Post by marcosdumay »

derefr wrote: post #77
yrro wrote: post #76

Earlier quoted context omitted.

What do they all do!?

I would guess that they're basically directly exposing the modem's ACPI device subtree over USB, the same way they would over PCIe. So you've got one endpoint corresponding to the data TX DMA region; one corresponding to the data RX DMA region; one corresponding to the command IO stream input; one corresponding to a command error channel; one corresponding to each different axis of mode-setting; etc.

Well, this design is better than the alternative.

Composing simple devices in a hierarchical address is much better than the old complex devices that had everything explained on the same datasheet, but it had 300 pages and no two devices were alike.

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

#94

Post by OrgNet »

groovybits wrote: post #33

From a Pi consumer perspective, this is not that big of a deal. However, it damages the purpose (in name) of USB C. Isn't C supposed to be the 'all purpose' spec? If we have popular manufacturers failing to follow the spec, we end up with cables marked as 'compatible with Raspberry Pi' or 'compatible with Nintendo Switch'. To the average consumer (and even most techies), USB C was supposed to be the 'one size fits al…

All purpose spec will be a round connector

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

#95

Post by cesarb »

TazeTSchnitzel wrote: post #82
teilo wrote: post #72

Earlier quoted context omitted.

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.

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

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).

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

#96

Post by oceanswave »

silversconfused wrote: post #83
teilo wrote: post #72

Earlier quoted context omitted.

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.

Too complex and overreaching is certainly a valid fault.

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?

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

#97

Post by cesarb »

mrguyorama wrote: post #56
gambiting wrote: post #22

Earlier quoted context omitted.

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.

Doesn't this mean that you can't use the Branded power supply with anything else? I'm so used to all my micro-usb (and hell, even mini and normal USB) based power delivery systems being 100% compatible, save using a 0.5amp supply simply won't charge my old phone as quickly as a 1.8 or whatever amp supply. Is this untrue in the world of USB C? I haven't experienced any oddities yet with my Pixel 2

The design mistake is on the RPi side, not the power supply side; their branded power supply should work with anything that needs at most 15W (3A @ 5V).

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

#98

Post by rrss »

dsfyu404ed wrote: post #67
hanniabu wrote: post #50

Earlier quoted context omitted.

Would be nice if they at least had a code on them to know what the compatibility is, such AV means the port is audio and video compatible, AVP would mean the former plus you can use it to charge or power a device. The same codes could be used on the cables as well.

And then you'd get and arms race that leads to "USB C AVPDEFWXYZLGBTQ" cables and ports that are compatible with every possible use and eventually everyone would just use those thus fulfilling the goal that USB C had in the first place.

> AVPDEFWXYZLGBTQ

RISC-V, is that you?

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

#99

Post by makomk »

seiferteric wrote: post #12

Is it possible to fix? Sounds like it's just missing a resistor? Break out the soldering iron and maybe could it could be salvaged.

The problem isn't just the missing resistor, it's that two pins are tied together when they shouldn't be. I don't think it's feasible to fix that on such a dense multilayer board.

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

#100

Post by jlarocco »

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.

As a consumer I think it's a big problem. Having identical ports that work differently is even more confusing than having a half dozen different ports. I can look at a micro-USB cable and a mini-USB cable and tell in 2 seconds which one works with the device I have - I can't do that if the ports look the same but behave differently.

It's enough of a usability fail that I won't buy one until it's fixed.

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