How does usb device with type-c receptacle detects, that plug (just bare usb type-c plug, without cable, and resistors) is attached?
Does USB specification describe this possibility?

I know, that my phone(sm-520f) somehow detects plug insertion, because I'm able to read MUIC registers, and it changes upon plug insertion.

Note: This question is NOT about CC pin detection sequence.

  • \$\begingroup\$ Why don't you read the specification? \$\endgroup\$ Commented Aug 25, 2019 at 9:53
  • \$\begingroup\$ @LeonHeller, in specification I only found detection sequence involving cc pin, which is not my case, but I'm not 100% sure it's not described. Why minus? \$\endgroup\$ Commented Aug 25, 2019 at 13:10
  • \$\begingroup\$ the minus is for no description of your effort to answer the question ... it is same as people posting a homework question without any effort to solve \$\endgroup\$
    – jsotola
    Commented Aug 25, 2019 at 15:50
  • \$\begingroup\$ What do you mean under "bare plug"? What particular kind? Are you sure there is no e-Marker on CC pin? \$\endgroup\$ Commented Aug 25, 2019 at 21:38

1 Answer 1


USB Type-C connectors have 4 pins for ground, and 4 pins for VBUS. By specifications, all similar pins must be connected together on PCB. Same requirement is for Type-C plug, VBUS pins and GND groups must be tied together "when mounted onto PCB".

However, it is possible to free one of pins (in VBUS or GND group) on mainboard and use it to check whether it is tied to the rest of pins or not. When "mounted plug" (not "raw plug") is plugged in, the host will be able to detect this. Technically this will be a slight violation of the letter of USB Type-c specifications, but who cares?

  • \$\begingroup\$ I used this plug mounted on the extension board , I guess this can be considered as "raw" plug (will double check this, when I'll be at home) \$\endgroup\$ Commented Aug 26, 2019 at 7:06
  • \$\begingroup\$ Hello, just wanted to say that I love you. I have been looking at this, messaging distributors left and right. Thought about using a hub with pd support, disconnecting vbus and gnd and doing measurements (but depending on some devices I wouldn't have any current consumption and lots of special cases), but I didn't think "far" enough to come up with this. Thanks a million. \$\endgroup\$ Commented Jun 30, 2023 at 18:28

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