I feel like the USB committee might be somewhat to blame. When most people think USB-C they're just thinking the cable. Why can't it just do regular slow charging with C to C cable?

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snops 5 days ago | parent | next [-]

It can, it just needs the two resistors, which is the cheapest possible thing the standards committee could have asked manufacturers to do.

USB-C gets complicated at the high end, but for basic functionality I think the standards committee did a very good job at making the cheapest way to do it the correct way, e.g. a USB-C to 3.5mm audio adaptor can be entirely passive, it just needs the right resistor in it.

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RobotToaster 5 days ago | parent | next [-]

Then a lot of phones don't support it, so it took me three attempts to find a usb-c to 3.5mm adapter that didn't have it's own DAC that would work with my phone's FM radio lol

	▲	kevin_thibedeau 4 days ago \| parent \| next [-]
		Audio Adapter Accessory Mode was deprecated last year so devices using it will be disappearing.
	▲	silisili 4 days ago \| parent \| prev [-]
		Do you mind sharing? I was looking for something like this a couple years ago.

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DoctorOetker 5 days ago | parent | prev [-]

>e.g. a USB-C to 3.5mm audio adaptor can be entirely passive, it just needs the right resistor in it.

How does that work? is each USB-C host port, or downstream USB-C hub port required to contain a stereo DAC? Does the standard impose performance requirements like dynamic range, noise, minimum sample rate,...? Does it also mandate the jack can be used for mic / line-in? Does it similarily stipulate inclusion of an ADC in each port?

	▲	jadamson 5 days ago \| parent [-]
		It doesn't mandate any of that, it's an optional feature. The data pins are repurposed for analog audio, so it won't work with hubs. You'd of course need a DAC for output and an ADC for mic input, but the point is to replace a headset jack, so you'd have those already. https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%... (PDF, page 309)

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alright2565 5 days ago | parent | prev | next [-]

The PCB designer could simply type "Type-C电路图" into Baidu and follow the instructions in the top result. But they couldn't be bothered.

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Zak 4 days ago | parent | prev | next [-]

Maybe, but there's no good excuse for this making it past the prototyping phase. If nobody plugged it into a USB-C power supply and noticed it doesn't work, that's negligent.

By 2019 or so, when USB-C was five years old, somebody on any product design team should have been aware this is a common problem and checked for it when selecting components.

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Iulioh 5 days ago | parent | prev [-]

It's not the usb c committee problem, the devices you are buying are out of spec

This is because the cable is 2 sided so it can't assume polarity

So it's a tradeoff for not having to guess how to insert the cable

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rcxdude 5 days ago | parent | next [-]

>This is because the cable is 2 sided so it can't assume polarity

Not really. The USB-C connection pinout is symmetric about a 180 degree rotation, at least as far as power connections go. It's entirely possible (and common, e.g. when using passive converters) to just put power out of it constantly. The main reason for the signaling resistors is to avoid having power presented on the pins when it's not connected, which is more about avoiding corrosion or wear due to small sparks on connection.

	▲	danhor 5 days ago \| parent \| next [-]
		And to avoid having two sources (perhaps with slightly different voltages) connected together and leading to hijinks. E.g. a usb A-C cable plugged into a USB-C power supply.
	▲	degamad 4 days ago \| parent \| prev [-]
		By 2-sided, OP probably means that the problem is that the cable has two USB-C ends, not that the USC-c connector is symmetric. If you have an A end and a B or C end, you can assume that the device on the A end is supplying power and the device on the B or C end is consuming power without breaking anything. The A end cannot supply power to it's device by design, so an A to C cable cannot be used to power the A device from the C device, regardless of whether the device on the C end can supply power. But if you have two C ends, you need some way to establish which device is the supply device and which is the consuming device, because the cable can be used to connect two devices which both can supply power (e.g. a laptop and a phone).

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Findecanor 5 days ago | parent | prev [-]

> This is because the cable is 2 sided so it can't assume polarity

To clarify (and to tell my own tale on the topic):

The power pins on both sides should be connected in both a plug and in a socket. However, when it comes to the USB 2.0 data pins only the socket end must be double-sided (short A6 to B6 and A7 to B7).

Back when "Type C" was new, I wanted to build a project with it, so I got one of the first socket breakout boards available. I built a mechanical keyboard out of aluminium with a slot milled to fit that breakout board. After everything was painted and soldered did I plug it in and it did not work ... It took me a while of troubleshooting before I retried it with the cable plugged in the other orientation. The breakout board had connected only A6/A7. B6/B7 were not available.