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USB Power Delivery: Plugging into the Benefits

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Re: USB Power Delivery: Plugging into the Benefits

#81

Post by vel0city »

JMiao wrote: post #51
edent wrote: post #2

I've basically stopped buying any portable electronics unless they take USB-C. Currently travelling with a laptop, watch, toothbrush, eReader, camera, bug-bite treater, and phone - all charging from the same power brick. I'm guaranteed of getting a replacement cable / charger wherever I am in the world if I need it. The only slight snag is some cheaper itema refuse to use PD and insist on plain 5V/2A - buy most decen…

we are talking about a lightweight charging cable. you can carry more than one. boom, redundancy. being ideological about a cable connector is the nerdy equivalent of jony ive obsessing over macbook thinness.

The number of times I went on a week-long vacation as a kid only to find out I didn't have just the right cable to charge my whatever-portable-entertainment thing was way too high. Oops, not the right cable for the portable DVD player. Oops, not the proprietary Gameboy SP adapter. Oops, not the right cable for the camera. Oops, not the right cable for the Genesis Nomad.

Forget that noise. Now its all one cable. Laptop, game console, phone, wireless headphones, reading device, even things like flashlights and lanterns. All one cable, can all work with the same extra battery packs and the same power cords.

Re: USB Power Delivery: Plugging into the Benefits

#82

Post by edent »

mcsniff wrote: post #9
edent wrote: post #2

I've basically stopped buying any portable electronics unless they take USB-C. Currently travelling with a laptop, watch, toothbrush, eReader, camera, bug-bite treater, and phone - all charging from the same power brick. I'm guaranteed of getting a replacement cable / charger wherever I am in the world if I need it. The only slight snag is some cheaper itema refuse to use PD and insist on plain 5V/2A - buy most decen…

I'll bite. What type of watch do you have that has a direct USB-C port on it?

This one - https://shkspr.mobi/blog/2025/08/i-bought-a-16-smartwatch-ju...

No need for a magnetic dongle. I literally shove a USB-C cable in there, charge for a couple of hours, then get a week+ of use. Does step count, notifactions, calls, etc.

There's more to the world than Apple and Android watches.

Re: USB Power Delivery: Plugging into the Benefits

#83

Post by edent »

codethief wrote: post #41
edent wrote: post #2

I've basically stopped buying any portable electronics unless they take USB-C. Currently travelling with a laptop, watch, toothbrush, eReader, camera, bug-bite treater, and phone - all charging from the same power brick. I'm guaranteed of getting a replacement cable / charger wherever I am in the world if I need it. The only slight snag is some cheaper itema refuse to use PD and insist on plain 5V/2A - buy most decen…

What toothbrush do you have? I've been looking for a USB-C charger for mine (standard Oral-B toothbrush) but the only ones I've found were from no-name Chinese brands and didn't work at all.

This one. No separate charger, just plug the USB-C cable in to the toothbrush.

https://www.amazon.co.uk/gp/aw/d/B0F8BD3922

Re: USB Power Delivery: Plugging into the Benefits

#84

Post by ssl-3 »

exmadscientist wrote: post #18
duskwuff wrote: post #17

Earlier quoted context omitted.

> By "that mode", do you mean "1.5A @ 5V" permitted by BC Neither - OP means devices with missing CC resistors which will fail to charge with a compliant PD source. (The A-to-C cable works because it provides 5V Vbus unconditionally.)

The A-to-C cable often does not work because the resistors are supposed to be in there . So if you are having complete charge failures, try a different cable.

That's close, but it's not quite complete. There seems to be lots of confusion here, and that's natural: It is confusing.

For just-getting-power from a USB A port into a USB C peripheral: There are supposed to be 2 resistors in the peripheral device [always], and also 1 resistor within the cable for USB-to-legacy cables[1]. That's 3 resistors, total, to get a relatively dumb USB-C equipped peripheral device to reliably charge from both USB A and USB C hosts/chargers/whatevers:

The cable itself: It gets an internal 56k pullup resistor between Vbus and USB C pin A5 -- which is the CC line [yes singular]). This resistor signifies the capabilities of the host/charger/whatever for devices that care (some do care, some do not care).

The peripheral: This minimally needs two pulldown resistors [commonly 5.1k], between each of CC1 and CC2 [yes a plurality] and ground[2]. This tells a compliant USB C host/charger/whatever "It's OK! Send the juice juice!" regardless of connector orientation.

[1]: https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%... section 3.5

[bleh]: Again, it is a confusing thing. Nobody said that dealing with such flexible, ambidextrous connections would be simple. CC performs a lot of different tasks: It can be a bidirectional serial bus for active PD negotiations, and/or a resistor network for passively dealing with power, and it's the bit that performs detection of cable orientation for applications where that matters, and it probably does other stuff too.

That single little wire is clever AF. It'd be simpler to use multiple wires instead of just one, but that would take more copper. Copper is expensive, and we each save a tiny bit of money (or a large pile of money globally) by using less copper instead of more of it.

Re: USB Power Delivery: Plugging into the Benefits

#85

Post by ThatPlayer »

chocolatkey wrote: post #75
ranger207 wrote: post #55

Earlier quoted context omitted.

I have a couple like that in my mini rack. The problem is the power supply: these take 65W, so I figured I could get a quality 140W charger and power them both, but it turns out that things like "unplugging something else" would kill their power. I had to spend a lot more on a StarTech charger to get the performance I needed

Which startech product did you end up getting? One of the hubs or chargers? I have a similar issue with various USB-C rack devices

Jeff Geerling has done a review and follow-up on one: https://youtu.be/twoAW0eLiXY

I've considered just getting a bunch of 65W USB-C buck converters and DIY one.

Re: USB Power Delivery: Plugging into the Benefits

#86

Post by exmadscientist »

crote wrote: post #70
exmadscientist wrote: post #38

Earlier quoted context omitted.

I was speaking a little more towards the AliExpress end of things, which is a sadly high proportion of the devices out there. For the midsize CMs and up, you're right, they've got piles and piles of stuff and don't charge by the reel loaded. 5.1k is a surprising resistor value, a lot of modern designs don't really have anything else in that area. I'm often not able to combine anything with it when I'm cost reducing.…

Heh, I would've argued the opposite. 5.1k is about the middle of the generic "some kind of pullup" range of 1k-10k, so it's a perfectly fine option for strapping resistors or for a non-critical I2C bus. 4.7k would of course have been better because it's an E6 value (+-20 via the spec) rather than E24, but it's still a value I would expect any PCBA house to have in stock at all times. But I agree, 1k or 10k would be t…

The 4.7k "default pullup" is an old-school 5V TTL thing. It works really well for TTL inputs. But CMOS inputs don't really care very much, especially if they aren't toggling or if there's a bit of hysteresis on the input stage (which there often, but not always, is). There seem to be 10k resistors in every design so CMOS pullups often end up at 10k. If power savings are a concern, especially if you need a tie-off more so than a pull resistor, 10k-100k is a perfectly valid range, and I've even used 1M in extreme circumstances.

Usually 5k is a little too weak for I²C. Rule of thumb is that you want to be around 1mA, so for a 3.3V system you start at 3.3k. Generally 1.8k to 3.3k ends up being a pretty common range. More current is usually better than less current, so even at 5V where 4.7k might be OK (if you're even at 5V Vdd these days), going stronger is often a good idea. If power savings is a concern, or if timing's somehow important (did you find another touchy badly behaved I²C device? say it isn't so!) then it might be time to break out the active pullup structures (mostly current source type things). Once this is done and tested it tends to get fossilized, for good reason, so this one won't usually get swept up in a standard-effort cost reduction pass.

Re: USB Power Delivery: Plugging into the Benefits

#87

Post by dreamcompiler »

edent wrote: post #2

I've basically stopped buying any portable electronics unless they take USB-C. Currently travelling with a laptop, watch, toothbrush, eReader, camera, bug-bite treater, and phone - all charging from the same power brick. I'm guaranteed of getting a replacement cable / charger wherever I am in the world if I need it. The only slight snag is some cheaper itema refuse to use PD and insist on plain 5V/2A - buy most decen…

TIL you can treat bug bites with something electrical.

Re: USB Power Delivery: Plugging into the Benefits

#88

Post by dabluecaboose »

helterskelter wrote: post #46
dabluecaboose wrote: post #35

Earlier quoted context omitted.

Oh man, please tell me it wasn't the CC GP-7. I have the micro version and have been hemhawwing about updating it.

You mean the CountyComm? If so, I'm 99% certain that radio is a rebranded Tecsun PL-360, which is in fact a 5V. I love Tecsun, but why they would cheap out on the USB-C refresh is beyond me. https://www.tecsun-radios.com/product/pl360-radio-receiver/

Looks more like the 368, but yeah. Good call!

Sounds like the juice may not be worth the squeeze on a USB-C refresh if I have to use an A-to-C cable for it anyway

Re: USB Power Delivery: Plugging into the Benefits

#89

Post by exmadscientist »

ssl-3 wrote: post #84
exmadscientist wrote: post #18

Earlier quoted context omitted.

The A-to-C cable often does not work because the resistors are supposed to be in there . So if you are having complete charge failures, try a different cable.

That's close, but it's not quite complete. There seems to be lots of confusion here, and that's natural: It is confusing. For just-getting-power from a USB A port into a USB C peripheral: There are supposed to be 2 resistors in the peripheral device [always], and also 1 resistor within the cable for USB-to-legacy cables[1]. That's 3 resistors, total, to get a relatively dumb USB-C equipped peripheral device to reliab…

My point, which matches what you've written out in more detail, is that there's supposed to be stuff (resistors) in the cable, stuff which is often not there. There are plenty of these abhorrent cables in the wild. And when you come across one, things get weird, because some sources and sinks deviate from the standard in ways that make them work with these bad cables. Others don't do that. (I believe there were a lot more abhorrent cables in the early days, and thus began the chain of accommodation....)

So unless your cable is known-good, if you are having trouble, trying a different cable should be the first thing you do. It really does often get things working.

Contrarily, if you have identified a naughty cable, it should be immediately widlarized.

Re: USB Power Delivery: Plugging into the Benefits

#90

Post by stephen_g »

seba_dos1 wrote: post #54
mschuster91 wrote: post #42

Earlier quoted context omitted.

> Usually the best place to fix it is by getting rid of the bad cables. Usually. No. There is no USB-C to C cable that will charge a badly implemented device with a standards compliant charger. That is the entire point. An USB A to C cable is completely standards-compliant and safe, even if it always supplies 5V on the C end - any standards compliant USB-C device should not activate the MOSFET on its Vbus line unless…

They mean bad USB-A to C cables with no resistor on CC line. Of course this is broken junk which will work with some devices and won't with others. I've also seen cables with resistors on both CC lines, which is also broken but in a slightly subtler way.

But it’s not what anyone was talking about. Such a cable should be really quite rare because it’s unlikely to work at all in most situations, whereas devices with USB-C ports that don’t work with PD chargers (due to a cent’s worth of missing Rd resistors) are irritatingly common, because they do work with USB-C to A cables!
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