Hey guys i cant find any usefull guide on how USB c charging works in depth. In particular i have bought a pair of Sony headphones which i would like to make wireless change so I also bought a crappy wireless coil meant to convert a phone into wireless charging. i opened the headphones, located the ground and 5v pin coming from the USB connected the circuit and surprise the charging led doesn't light ... The charging board is separated from the main board so I checked the flat cable that connects them, found the 5v and gnd ,spliced into it, and the led light lit as if it was charging. the next morning the led was of signaling the headphones are full, unfortunately after powering them on the battery status indicated was still 20% as the evening before ... Have I done anything wrong ? What about that phase when they negotiate the power output with a magic resistor ? What should I try next? Thanks in advance ๐๐ป
I will note that I'm not an expert in the plethora of USB charging standards. Quite frankly, USB C is almost like black magic to me. With that said, finding the D+ and D- lines might be tough unless you've got a USB C charging cable you're willing to cannibalize.
That is, what you can do is carefully splice into such a cable, then connect it to the board and a USB charging block. By probing the wires, you can rule out the power wires, which should leave you with the D+ and D- wires. You would want to do this with a cable that's meant only for changing, such as USB C to USB A. That way, there would only be four wires inside. If you cut open a USB C to C cable, you'll have a lot more wires that you have to check.
Once you identify the D+ and D- this way, you can then do continuity checks from those wires to various pads on the board. In this way, you'll eventually find your D+ and D- pads, and can then add your temporary resistors, to see if that works.
As for identifying the USB charging spec in use, that's going to be tougher. I think there are test devices that take the place of a USB charger and can display or change the spec, but I've never used such a thing.
Thanks so much for your help I will make some tests and hope for the best I now at least know that's a lot more complicated that what it seems yeah definitely black magic to me too ๐ kinda ironic the universal name if u then have thousands of different standards