The Raspberry Pi 4 offers OTG functionality using the USB-C port which is normally used for power only. Therefore, for the PIKVM a special Y-cable is required and can be soldered as can be seen in this tutorial:

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Is this way safe and correct? Since VBUS is disconnected, no reverse current can flow either from the host back to the Raspberry or from the power supply to the host. Only the Raspberry is powered, so I would assume this is safe.

I wonder that because I have also seen this splitter which makes use of Pu/Pd resistors, but I don't understand why.

  • \$\begingroup\$ This is fine but you need to add those resistors, because that tells the power source port how much power is required. It may work without those depending on the power source \$\endgroup\$
    – BeB00
    Feb 10 at 2:10
  • \$\begingroup\$ Isn't the power required by the power supply already told by the Raspberry PI 4's USB-C port? I will be using the original 5.1 V/3 A power supply. \$\endgroup\$ Feb 10 at 2:16
  • \$\begingroup\$ it is, but you have disconnected the raspi usb C port from the power source, so how would it know? \$\endgroup\$
    – BeB00
    Feb 10 at 2:18
  • \$\begingroup\$ The Raspberry Pi's USB-C port acts both as OTG and power, so it always receives power but it additionally uses D+ and D- to interact with the host. The normal USB-C power supply would only have two wires, one for VBUS and one for GND. \$\endgroup\$ Feb 10 at 2:28
  • \$\begingroup\$ in that case, whichever charger you're using doesn't care about power negotiation, so this would be fine. If the charger was following the USB specification, it would require those resistors. The board you linked would work with standard usb ports - in theory your solution would not (although many host devices will provide current without negotiation (however usb-c has become a bit more strict about this) \$\endgroup\$
    – BeB00
    Feb 10 at 23:40


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