3 ms·
Is it really that simple? Just changing a resistor value? I got an XPS 13 for work, it’s all USB-C, and the versatility of the port is fantastic (doesn’t matter
by ljm 9y ago
Is it really that simple? Just changing a resistor value? I got an XPS 13 for work, it’s all USB-C, and the versatility of the port is fantastic (doesn’t matter which port I plug into, it still charges, so I don’t have to wrap the power cable around the back of the machine or sit in a weird position to keep some slack in the wire). However, I took it to the office and naturally I plugged my power adapter into one port. I then plugged in the monitor (also USB-C, delivering power), and the two ports cancelled themselves out and confused the OS. Windows thought I was charging the laptop yet it also said the battery was depleting. They were negating each other and the battery loss continued as it would with no power connected.
It makes sense for a monitor to power the laptop because it’s mains connected. But then you have one of those classic programming problems: if there are multiple inputs providing the same thing which do you consider the source of truth?
- criddell 9y agoThey could always ask the user if they are that confused then remember the answer so they don't have to ask again.
- ljm 9y agoCan you imagine a typical laptop user who assumes everything 'just works' (like me, by virtue of thinking I need to power my laptop while attaching a powered monitor) seeing a prompt in the OS about which thing should provide power and which should either reject it or use it to charge a battery?
- acct1771 9y agoCan you imagine someone not understanding a clearly worded UI that they use to do the things they have to do to function in society?
- dmoy 9y agoThere are some USB c complaince issues which are yes literally just the wrong resistor. What you're describing might go beyond that though, in particular if there's multiple ports and hubs involved, that could be not just a usb problem.
- nol13 9y agoHmm, this have anything to do with why trying to hook up my macbook to external monitor with usb-c to display port cable blew my motherboard today?
- samhain 9y agoUSB PD requires communication over the CC pins via setting different resistor values and checking them at specific times in the hand shaking process. The communication in the latest spec is supposed to happen at about 300kbs using a specific protocol on a specific CC line. There have been multiple specs since about 2011, some of which used communication over the VBUS line using BFSK, which has since been deprecated. This adds to the confusion.
- kalleboo 9y agoOn Macs, it will choose the power supply that advertises the highest available wattage. This has been working flawlessly on my MacBook Pro.