I need clarifications about which USB receptacle and plug I have to use for an embedded product.
- If I want to realize an embedded product with device role, I have to use mini or micro USB B receptacle. So I can connect my device to an host using a cable with a mini or micro USB B plug and a USB A plug.
- If I want to realize an embedded product with host role or OTG, I have to use mini USB A or micro USB AB receptacle. So I can connect a device like a PenDrive at my embedded product with a cable with mini or micro USB A plug and a USB A receptacle; if my embedded is an OTG I can also connect its to an host with a cable like previous case (and checking the ID pin).
If yes I have 3 questions:
- If with mini or micro USB B receptacle my embedded product must to have a device role, why in the receptacle connector there is also the ID pin that can be tested by microcontroller (and so switch from device to host role)?
- Only the cable with mini or micro USB A plug and a USB A receptacle are USB compliant?
- If I'm not mistaken, many smartphones a few years ago had a receptacle mini or micro USB B but, with a particular OTG cable, they could take the role of host and read for example a PenDrive. In this case all these smartphones are not USB compliant?
Thank you in advance.