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USB-C head-to-head comparison

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Re: USB-C head-to-head comparison

#161

Post by crote »

c-linkage wrote: post #94
lxgr wrote: post #78

Speaking of USB-C 10 Gbit/s cables, I've noticed something odd about the iPhone 15 Pro: I have a USB-C cable that has been yielding 10 Gbit/s speeds (i.e. USB 3 Gen 2x1 or possibly but very unlikely 1x2) when used at my Mac with various devices (mostly SSDs). However, that same cable only gets USB 2 speeds when connecting the iPhone to my Mac. The iPhone itself also seems to only get USB 2 speeds using the SSD and th…

I figure the reason the Apple USB-C cable has a complex PCB embedded in the head-end of the cable is to detect Apple-certified devices and ensure top speed only when paired with an Apple-certified cable. Both the device and the cable have to recognize each other as properly licensed devices, otherwise you get sub-standard performance.

No.

Doing 40Gbps data is really hard because physics. Once you get beyond about 100cm, the signal loss basically requires you to add a repeater or retimer. This has been part of the USB-C specification since the very beginning, and any cable of this length doing 40Gbps will feature a similar PCB.

Re: USB-C head-to-head comparison

#163

Post by fireflash38 »

moonfern wrote: post #142
bloopernova wrote: post #3

I wish these were more widely available: https://caberqu.com/home/20-42-c2c-caberqu-746052578813.html... I have one from the kickstarter, and every new USB-C cable gets tested and labeled. Most are USB 2.0. A few will have the power delivery pins. It's such a crapshoot on any shopping site. It should be mandatory that these cables are correctly spec'd and labeled.

"USB-IF strongly discourages its members and the industry at-large from using specification names/terminology in consumer-facing branding, packaging, advertisements, and other marketing materials." They recommend the following naming: XYZ's USB 40Gbps 60W USB Type-C® Cable or USB 40Gbps 60W USB Type-C® Cable USB 40Gbps... correspond to the USB4 Gen 3×2 mode Hi-Speed USB is USB 2.0 (High-Speed). A tip usb cable and a…

What a clusterfuck of branding. The inability to easily differentiate between capabilities makes everything the same as the lowest common denominator - the shittiest USB-C cable from wish.

Re: USB-C head-to-head comparison

#164

Post by ivanjermakov »

mensetmanusman wrote: post #48

“ Another curiosity hidden in the circuit board is this wiggle on one of the traces. It contains a tiny detour to make sure it’s the same length as its paired trace, which is especially important when dealing with extra-high-speed data transmission.” A wiggle that small is adding picosecond delays. I’m surprised that’s necessary. Cool!

Today I learned! I'm curious to see approaches to solving optimal pathing of traces to keep them equal length.

Re: USB-C head-to-head comparison

#165

Post by crote »

avianlyric wrote: post #44
Tempest1981 wrote: post #32

I'm curious about the 9-layer PCBA -- is it an amplifier or signal conditioner, to achieve 40 Gb/s? Or does it implement some protocol? Or for power delivery? I see what might be resistors or capacitors. Not sure what else.

It’s most likely 9-layers because that what you need to correctly route the traces from one set of 12 pins, to the other set of 12 pins (to make up the 24 total in USB-C), which is needed to make the connector fully reversible. There will also be a e-mark chip in there that tells any connected device what the cable is capable of doing, so you don’t accidentally send 240w down a cable only capable of carrying 100w. 9…

That's not how USB-C works.

Unlike Apple's late Lightning connector, USB-C isn't two sets of mirrored pins. The power pins are simply shorted together on both sides, four pins each for VBUS and GND. USB2 and CC (connection detection) are connected only on one side. The remaining pins are four high-speed lanes, two per side.

With rare exceptions, a USB-C cable does not do anything about reversibility. It simply connects the pins straight-trough to its partner on the other plug. The lane swapping needed for the high-speed lanes is done by the devices, not the cable.

The Apple cable is so complicated because it is a 40Gbps cable over 100cm long. This means it requires a redriver to guarantee signal integrity. That's what the big chip is for. Doing that in the small space available in a plug means your routing gets complicated.

Re: USB-C head-to-head comparison

#166

Post by crote »

oaiey wrote: post #133
gkfasdfasdf wrote: post #80

This really highlights one of the disadvantages of everything going to the same physical port - it's not easy to tell what the capabilities of the port and cable are.

It is a weakness of the USB consortia paper process to not enforce labeling on their hardware, cables and ports. Same physical port does not really matter. Also operating systems could help with clarifying the ports without special tools. Would be so easy.

The USB-IF already has labeling guidelines[0], pretty much all manufacturers just chose to completely ignore them.

[0]: https://www.usb.org/sites/default/files/usb-if_usb_type-c_ca...

Re: USB-C head-to-head comparison

#167

Post by namtab00 »

pipeline_peak wrote: post #85

I love the fact they call the lightening cable an “11 year reign”. There’s a part of Apple that capitalized on hidden reservoirs of tech and talent. Then there’s a part of Apple capitalizes on its own reputation and history. Lightening cable feels newton era.

"lightening" as in pocket-lightening?

Re: USB-C head-to-head comparison

#168

Post by crote »

kibwen wrote: post #151

> This is the only cable we scanned that contains no PCBA; the pins just connect directly to the wires. What is the PCB for if it's technically possible to omit it?

Signal integrity and ease of assembly. There's a lot of very high-speed connections really close together, which means they are going to interfere with each other. The "paddle card" allows you to maintain signal quality while you are spacing them out a bit for the wire connection.

This isn't nearly as important with USB-2-only cables, which makes the direct soldering possible. It's going to require making a custom connector, so it's not really surprising a lot of manufacturers just reuse the high-speed ones and stick with a paddle card.

Re: USB-C head-to-head comparison

#169

Post by simondotau »

mensetmanusman wrote: post #48

“ Another curiosity hidden in the circuit board is this wiggle on one of the traces. It contains a tiny detour to make sure it’s the same length as its paired trace, which is especially important when dealing with extra-high-speed data transmission.” A wiggle that small is adding picosecond delays. I’m surprised that’s necessary. Cool!

My (deeply uninformed) guess is that it probably wasn't absolutely necessary, but would be one among a hundred tiny details which improves resilience. There was space for it. And it has a $0.00 unit cost. It'd be more surprising if they didn't do it.

For Apple, perhaps the most economically exposed to customer problems of any major tech company, and has enough scar tissue from past failures, it's not surprising that their products tend to feature first class electrical engineering. Their DC chargers are widely regarded as among the best in the industry.

Re: USB-C head-to-head comparison

#170

Post by scarface_74 »

lxgr wrote: post #78

Speaking of USB-C 10 Gbit/s cables, I've noticed something odd about the iPhone 15 Pro: I have a USB-C cable that has been yielding 10 Gbit/s speeds (i.e. USB 3 Gen 2x1 or possibly but very unlikely 1x2) when used at my Mac with various devices (mostly SSDs). However, that same cable only gets USB 2 speeds when connecting the iPhone to my Mac. The iPhone itself also seems to only get USB 2 speeds using the SSD and th…

There is no such thing as a compliant USB A to USB C adapter and some combination may fry your device.

https://hackaday.com/2022/12/27/all-about-usb-c-illegal-adap...

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