There are various information application products (IA) in daily life. Most of these products are designed to connect with traditional PCs and various IA devices, and their connection interfaces must be easy to use and freely plugged in so that everyone can use them without learning. This is the challenge that these cable-relative transmission protocols need to face.
USB OTG does not specify an additional communication protocol for connecting two OTG devices. What OTG regulates is that when two OTG devices are connected, one device can be used as the host and the other device as the device; this is the same as the original computer connection to the surroundings, but before the concept of OTG was proposed All devices can only be regarded as device ends.
When two OTG devices are connected, the original USB architecture does not provide a way for these two devices to determine who is the host. Therefore, OTG has added Mini-AB sockets, Mini-A and Mini-B connectors. It is used to make the OTG device decide to be regarded as the host side or the device side when it is initially connected. The newly added Mini-AB socket can be inserted using Mini-A and Mini-B connectors.
A new signal called “ID” is added to the Mini-A and Mini-B connectors. The pin ID in the Mini-A connector must be connected to the USB ground (GND), and in the Mini-B connector, it must be It is unconnected. Therefore, if the Mini-A connector is inserted into the OTG device, the ID will be a low potential. At this time, the OTG device is called A-device, and will initially become the host side. If a Mini-B connector is plugged into an OTG device, the OTG device is called a B-device and will initially become the device end. Therefore, the connection of the two OTG devices must be through a Mini-A connector to a Mini-B connector, so as to determine which side is the host end when connected. After the connection is established, the two OTG devices can switch the role of the host and the device through the HNP protocol.
