USB OTG – it´s better to be a master than a slave

USB OTG (On-The-Go) cable enables for example a simple connection of USB slave devices with a smartphone.
As we know, USB communications operates in such a way, that a Master (Host) device (usually a PC) controls all communication on the bus and Slave devices are only able to require attention. Slave devices are all common peripherials like printers, scanners, mouses, cameras, USB drives, mobile phones etc.

However, naturally there are situations, when we´d like to interconnect also devices, which usually operate in a Slave mode, for example a printer with a USB key, mobile phone with a USB key or with a keyboard etc. In this case we want one of the devices to act as a Master.
USB OTG solves this problem and enables to use a given USB device in a Master and in a Slave mode as well. A mode in which a device will operate is defined by wiring of an interconnecting cable itself (pin ID grounded or left floating). USB OTG is supported by many nowadays mobile devices, which can be switched to a Master mode by using of such a cable. That´s why, when you´ll use the USB-OTG cable, you can connect a USB drive, mouse, keyboard and other USB slave devices directly to your smartphone.
 
For more detail: USB OTG – it´s better to be a master than a slave