For old some micro usb devices, you can wire the ID pin so it is connected to the ground pin with a resistance of something like 36.5 kΩ. When the device is in host mode and connected to a device, this would allow the android host device to receive power from an external source when it was connected to the Vbus pin.

Basically, this allowed a device to be charged, while in host mode and still be in control of the peripheral device. I believe this kind of connection was known as accessory charging adaptors (ACA).

My question is, is there an alternative wiring to this for USB-C, can I buy some sort of adaptor, or even design some sort of board myself to go between a USB-C phone and a peripheral device?

  • \$\begingroup\$ Update, there is a board available from lavacomputers but generelly are only compatible with samsung tablets. They claim to be the only people on the market who do this. I don't really feel like pay 130 dollars for that adaptor plus shipping though, so a followup question I have is why aren't there more on the market? \$\endgroup\$ – Adam Higgins Sep 18 '19 at 9:32
  • \$\begingroup\$ lavasimulcharge.com/products/lavasync-usb-c-mobile-adapters/… \$\endgroup\$ – Adam Higgins Sep 18 '19 at 9:32

In modern USB environment a USB port carries two roles: data role, and power role. In USB Type-C framework the two roles are coupled/associated by default: host data role is associated with power supply role, and USB device is a power consumer.

Now, to make a host to act as consumer (to charge itself), the recent USB Type-C specification defines only one way to swap the power role while keeping the role as USB host. This way is to use a subset of power delivery specifications of so-called "Structured VDM" - Vendor Defined Messages. Typically the process is implemented by so-called "PD management IC" which provides PHY-level PD protocol communication over Type-C CC wire, all under control (typically over I2C) from an embedded controller. The overall protocol is quite complicated and is described in "USB Power Delivery Specifications" Rev3.0, which can be found in USB-IF document library.


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