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I am learning some concepts of USB OTG recently. When surfing wikipedia,I came to know that, OTG supporting devices are playing dual role and it will have mini AB type receptacle or micro AB type receptacle.

To act as a host, the OTG supporting device must be connected with mini-A or micro-A cable. To act as a device, it needs to be connected with mini-B type or micro-B type cable.

Wikipedia says -

"The device with a mini-A plug inserted becomes an OTG A-device, and the device with a mini-B plug inserted becomes a B-device (see above). The type of plug inserted is detected by the state of the ID pin (the mini-A plug's ID pin is grounded, while the mini-B plug's is floating)."

But doubt comes when I come across this image I attached. It has mini-B type receptacle for it's audio system. In order to insert a pendrive, the user need to have an adapter which should have mini-B type on one end and standard A type on the other end. So, possibly the audio system in the car can only detects that mini B type cable is connected with it. If this is the case, the audio system is supposed to works as a device instead of host.

But, the audio system detects pendrive and starts to play music from it. This is a chevrolet beat car audio system. Is this contradictory to the theory said in wikipedia?

clear out this doubt please?


1 Answer 1


There's literally thousands of products that abuse USB connectors in ways the USB standard explicitly forbids (very popular: external USB2 hard drives with USB-A as device-end receptable).

So, there's probably nothing wrong with wikipedia here, your car manufacturer just decided that standards are something for other people to adhere to.

  • \$\begingroup\$ From your statement, I can understand that the car manufacturer didn't follow the standard. But, i need more technically. How the audio system detects a pendrive when mini B type cable is connected with it? \$\endgroup\$
    – CNA
    Commented Mar 5, 2020 at 10:41
  • 1
    \$\begingroup\$ If the mfg doesn't follow the standard, you can't get that info from the standard. Either reverse engineer it, or ask the mfg. \$\endgroup\$
    – user16324
    Commented Mar 5, 2020 at 12:18
  • \$\begingroup\$ @CNA Brian is right, there's no telling. It probably just tries, or you simply got lucky. Maybe there's some magical thing that update devices that you might connect to that bus do differently. We can't tell. Nobody can. \$\endgroup\$ Commented Mar 5, 2020 at 12:29

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