Re:240W USB-C PD chargers are nearly here, says Framework CEO
by rektide on Friday June 09, 2023 @01:32PM
(#36261133)
> The reason some cheep chineese electronics with USB-C connectors can only charge with USB-A to USB-C cables, not with USB-C to USB-C cables is that they skipped the CC pins entirely.
If anyone has a usb-c pass through adapter that can negotiate for 5v out, please please please share. Ideally for me it'd be a like 3 inch cable that that a male & female connector.
Extra credit if it uses usb-pd to try to ask for 5v 5a.
(these would be incredibly out of spec & could cause damage to systems, but mercy they'd be useful! I find this problem to happen on a bunch of devices, alas not just cheap/rare ones)
Depending on what's on the other end, it's actually even better than that would imply most of the time.
If both sides of the cable are in spec-compliant USB-C ports, then the power pins will be left at 0v for the initial connection, and only the CC pins will have a minuscule amount of power coming from the source (charger) - just enough to detect specific levels of resistance on the sink (phone/laptop/etc.) for 5v power and/or negotiate a higher voltage for USB PD.
Once they've established that one side is a source and the other side is a sink, then the source will provide power on the power pins of the cable.
If a USB-C cable is used to connect one charger to another, for example, then the negotiation will fail and neither charger will provide power on the main power pins.
USB-A ports, on the other hand, always provide 5v, so USB-A to USB-C cables always provide 5v on the main power pins.
The reason some cheep chineese electronics with USB-C connectors can only charge with USB-A to USB-C cables, not with USB-C to USB-C cables is that they skipped the CC pins entirely. I actually modded one device by adding in two half-cent resistors to make it able to charge from a USB-C port: https://www.nfriedly.com/techblog/2021-10-10-v90-usb-c/