There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
This sounds solvable, doesn’t it? Have the extension cable have a chip saying it can do X at maximum, then compare with whatever is to be extended and communicate the minimum of both upstream. Might not become a sleek cable-like design, but would extend the 240W cable with the extender safely staying at 120W
That’s an active extension cable, which is essentially a single port USB hub.
Shouldn’t it be possible to only do the negotiation part and otherwise bridge everything? Not having to do anything high-bandwidth actively should keep the silicon costs down.
Yes, and such cables already exist, like this splitter cable:
https://www.amazon.de/dp/B0CRZ6JJ6D (not an affiliate link)
It’s not an extension cable, but it does exactly what you are suggesting. It gets the available PD profiles from the charger and then intelligently negotiates a profile that will work best to split the power to the 2 devices connected to it. The charger thinks it’s just connected to 1 device, and the connected devices think they are directly connected to a charger.
Doing the same for with a USB C extension would be trivial, but it’s probably hard to market such a cable when passive USB c extension cables are available at a fraction of the cost, even if those aren’t compliant to the USB standard
I wish there was a clearer explanation or nomenclature for this. With things like cables and converters everything always seems to have a black box layer.
I don’t understand why there are so many PD profiles either. Maybe Cat-1 USB-C, Cat-2 USB-C, etc? Maybe just having a smaller set of voltage-defined profiles that have a safe maximum current rating? Maybe that’s already how it is? I don’t know
There are technical reasons for why so many PD profiles exist.
In fact they were not enough, which is why the USB Standard was extended with the “PPS” extension recently, which let’s the attached device freely choose a voltage between 3V and 21V in steps of 20mv, and more importantly it let’s the device freely change this voltage without interrupting the charge process. This change makes it possible for devices to bypass their own but in charging electronics and just directly forward the voltage coming from the charger to the device, improving efficiency and significantly decreasing how much the device hears up during charging
Sadly PPS is not found on many devices or chargers yet, and makes the already complicated USB C charging situation even more complicated for consumers
I am highly sceptical of anything that would connect USB voltage, no matter how finely negotiated, directly to the battery terminals. Finely tunable voltage over USB is useful for keeping the buck/boost converter on the device side small, though, or just efficient because it doesn’t have to do as much work. If you can charge over standard PD extending to charging over PPS should only be a software change as your hardware is already more than capable.
Heh heh heh. Wait till you dive into the world of “That $15 cable costs 12c to make.”
Getting $30 cables for $3 with my employee discount was almost the only good thing about working for Best Buy in the early 2000s.
I’m right now in China and those cables cost $0.50 shipped to your address, so not surprised
Well, the source checks the cable using the CC line which doesn’t go through the cable (VCONN). So source only knows the cable directly plugged in. To make the extension cable visible, the sink would be required to check the cable plugged in using VCONN and then the tell max ampere to the source over the other CC that goes through the cable.
2 Problems:
Sink devices normally don’t read or can’t read VCONN as far as I know
No way of detecting if a third cable (extension in the middle) is present and what specs it has