Method and apparatus for automatically switching between USB host and device
An apparatus and method for automatically switching between USB host and device is provided. In a device with a USB interface, the present invention automatically switches between a USB host and USB device by detecting the handshake protocol of the D+ and D− pins of the USB interface. The apparatus for automatically switching between USB host and device includes ah host mode element, a device mode element, a random auto-switcher, and a detection element. The random auto-switcher switches the connection to the host mode element or the device mode element at random time. The detection element monitors the handshake protocol of the D+ and D− pins of USB interface and the external USB-interface device to determine whether the host mode or the device mode is in use. When the present invention detects the external USB-interfaced device is a host, the present invention switches to become a USB device. Similarly, when the present invention detects the external USB-interfaced device is a USB device, the present invention switches to become a USB host.
1. An apparatus for automatically switching between a USB host and a USB device, applicable to a device with USB interface, said apparatus comprising:
a host mode element;
a device mode element;
a random auto-switcher, for switching between to said host mode element and said device mode element at random time; and
a detection element, connected to said random auto-switcher, a VBUS pin, a D+ pin, and a D− pin of said USB interface.
2. The apparatus as claimed in claim 1 , wherein said USB interface is USB1.0, USB 1.1, USB 2.0, USB OTG or any combination of the above.
3. The apparatus as claimed in claim 1 , wherein said detection element monitors the handshake protocol between said D+ and D− pins of said USB interface and an external USB-interfaced device.
4. The apparatus as claimed in claim 3 , wherein said handshake protocol meets the standard defined by USB-IF.
5. The apparatus as claimed in claim 1 , wherein said detection element informs said random auto-switcher to switch between said host mode element and said device mode element.
6. The apparatus as claimed in claim 1 , wherein said detection element informs said random auto-switcher to stop switching and stay in the current mode.
7. A method for automatically switching between a USB host and a USB device, applicable to a device with a USB interface, said method comprising the steps of:
(a) a random auto-switcher randomly switching to a host mode element or a device mode element;
(b) said random auto-switcher informing a detection element to monitor a handshake protocol between a D+ pin and a D− pin of said USB interface and an external USB-interfaced device;
(c) said detection element determining whether said handshake protocol matches a current mode of said random auto-switcher;
(d) if matched in said step (c), said detection element informing said random auto-switcher to stay in said current mode, and not to switch; and
(e) if not matched in said step (c), said detection element informing said random auto-switcher to switch to the other mode, and then repeating said step (b).
8. The method as claimed in claim 7 , wherein said handshake protocol meets the standard defined by USB-IF.