I just went to charge my kitchen scale and it wouldn’t work until I dug out a USB-A -> C cable and plugged it into my desktop…
It just reminded me of how many devices like that I have. This scale, my wife’s sound torc, some car jumperstarters, and I think a one or two more…
I assume it’s because they just slap a usbc port on a dumb 5v circuit that doesn’t have a power negotiation controller. So the cable and the charger cant figure out the power needs of the device are and just never send any.
All of that because they couldn’t be bothered to put two resistors for the detect pin.
Remember, line must go up at any cost.
Bro have you SEEN the price of resistors lately?
……cuz I haven’t and I assume it’s fractions of a penny per.
But wait. Doesn’t this make them both dumb? I’d expect a modern USB-C charger to still support basic 5v low current lazy devices too. If there’s a USB-A to C cable that works, it must also still be possible to send the basic 5v down a C-C cable.
I also think there’s always going to be a balance between how much a device needs to make and/or how much it needs fast charging to make sense to add the charging circuit for PD/PPS. Even $1-2 on top of the cost can ruin margins in the current electronic market.
PD includes a 5v option, so you’d think that chargers would default to a dumb 5v/4.5w with no other input, but apparently not… It’s probably something to do with the overcharge protection, or to not (further) harm a device with a damaged charge controller.
Or it could be that my PD chargers are pre pandemic and PD 3.1 fixed this.
Well, I’d expect that if they allowed 5v through but with a low current limit (I think the default 5v standard states quite a low current allowance). They could catch anything drawing too much and shut the port off until it detects disconnection/other reset.
I mean, if they’re thinking about protecting a downstream device, adding this logic would make more sense than just not supplying any power unless a negotiation is made.
In any case, since standard USB ports on a computer will output 5v without anything being negotiated, then it’s really no less safe than any other USB port in that regard.
USB c has active negotiation for power and communication via a cc pin
The usb a to c cable has a pull up resistor that mimics this and says “give 5v”
Some usb c chargers have a fallback 5v mode for this scenario but not all do
This bothers me more than literally anyone, however as an ee I do feel obligated to explain their crime against humanity.
The usb pd charge negotiation chip costs between $.50 and $3, cheaper for low current, like 12-18w, more expensive for 100w, also those tend to have more logic including battery management and even integrated buck converters.
Still unacceptable by any standards, but there are software aspects like debugging how the different charge and power modes work together, etc.
Largely it’s inertia, buying a power brick and just putting a 19v is tried And tested, even though 20v is basically the exact same except for the pd negotiation.
The cheap ones assume you use the same cable that came with it, which are generally 2 wire only and have the resistor in the plug.
Way to complex and expensive. This just needs 2x 5.1 kOhm resistors between the CC pins and GND.
Yeah, the cheap cables they provide are often only vcc and gnd with the data pair shorted in the plug.
Trying to use a normal plug confuses the controller.
