Abstract:
A USB host/client system includes a USB host device, a USB client device connected via a USB cable to the USB host device, and a power supply unit remote from the USB host device for powering the USB host device through the USB cable connecting the USB client device to the USB host device. The USB host device can have means for communicating with a computer while the USB host device is connected to a USB client device, and/or the power supply unit supplies sufficient power for all normal operations of the USB host device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable  
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0003]     Not applicable  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     The present invention relates to universal serial bus (USB) devices. More particularly, the present invention relates to USB devices having unique power sharing capabilities.  
         [0006]     2. General Background of the Invention  
         [0007]     Normally, USB host devices provide power to USB client devices. The USB specification does not entertain the option of the USB client detecting and providing power to the host device.  
         [0008]     USB interface 2.0 specifies that USB host devices be able to provide power to a USB client device. Self-powered USB client devices typically use the power pin to detect the presence of a host USB device.  
         [0009]     A USB host device has resistive pull-downs (15K ohm) on both the D+ and D− signal lines. Typically a high/full-speed USB client device has a pull-up resistor (1.5K ohm) on the D+ line. A low-speed USB client device uses a pull-up resistor on the D− signal line. A high-speed USB client device uses a pull-up resistor on the D+ signal line. Part of the enumeration process for USB is deciding if the client is a high-speed device, full-speed device, or a low-speed device. When power is applied by the host device through the VBUS signal, the D+ and D− signals are either high/full speed or low-speed depending on the configuration of the pull-up resistor for the USB client device.  
         [0010]     When the D+ signal is high (4.5V) and the D− is low, the speed of the USB client device is high/full speed (printer, scanner, etc.). When the D+ signal is low and the D− signal is high (4.5V), the speed of the USB client device is low (mouse, keyboard, etc.).  
         [0011]     The following U.S. Patents, discussed below, are incorporated herein by reference: U.S. Pat. Nos. 5,767,844; 5,799,196; 5,844,086; 5,938,770; 6,000,042; 6,105,097; 6,128,743; 6,147,682; 6,170,062; 6,175,530; 6,189,040; and 6,205,502.  
         [0012]     U.S. Pat. No. 5,767,844 discloses a modified USB interface for allowing remote power up of a computer while permitting normal remote power down.  
         [0013]     U.S. Pat. No. 5,799,196 discloses a system for powering a computer in sleep mode by a USB device via a USB port (see especially claims  6  and  12 ; see also claims  7 - 10 ).  
         [0014]     U.S. Pat. No. 5,844,086 discloses a system in which non-standard voltages can be supplied through a USB cable to a USB client device.  
         [0015]     U.S. Pat. No. 5,938,770 discloses a computer monitor which has USB ports and can supply power to USB devices connected thereto.  
         [0016]     U.S. Pat. No. 6,000,042 discloses a USB controller with a fault detection circuit.  
         [0017]     U.S. Pat. No. 6,105,097 discloses a system for interconnecting USB devices (such as two computers) and managing the power consumed by each.  
         [0018]     U.S. Pat. No. 6,128,743 discloses a USB hub for interconnecting multiple USB devices with a USB host. The USB hub can be powered by the host or with its own power supply.  
         [0019]     U.S. Pat. No. 6,147,682 is similar to U.S. Pat. No. 5,938,770 and discloses a computer monitor which has USB ports and can supply power to USB devices connected thereto.  
         [0020]     U.S. Pat. No. 6,170,062 is a division of U.S. Pat. No. 6,000,042 and also discloses a USB controller with a fault detection circuit.  
         [0021]     U.S. Pat. No. 6,175,530 discloses a system in which a low power condition on an FPGA interface device interconnecting a target FPGA device and host system is detected via a USB connection, and power is supplied to the FPGA interface device by the target FPGA device. However, the power is not supplied by the target FPGA device through a USB cable.  
         [0022]     U.S. Pat. No. 6,189,040 discloses a data controller which interconnects a host computer with a plurality of client devices and directs transmission of data between the client devices.  
         [0023]     U.S. Pat. No. 6,205,502 discloses a USB controller with a switch to allow multiple USB devices to be plugged into the controller and recognized by the USB host after flipping of the switch.  
       BRIEF SUMMARY OF THE INVENTION  
       [0024]     There is a need to have USB client devices provide power to a USB host device yet still follow the USB specification of allowing a powered USB host to be attached. An example of a USB host device that should be powered by the USB client is a network adapter connected to a printer. This is particularly relevant if the network adapter is wireless (RF or infrared based).  
         [0025]     By using an additional device or module to detect the presence of a connected but un-powered USB host device, power could be applied to the USB VBUS pin to power up the USB host device and provide the USB client device the proper indication that a powered USB host device has been plugged in.  
         [0026]     The present invention allows for a USB client device to detect and provide power to a USB host device.  
         [0027]     The present invention includes a USB host/client system comprising a USB host device, having a USB port for connection to a USB client device; a USB client device connected via a USB cable to the USB host device; and a power supply unit remote from the USB host device for powering the USB host device through the USB cable connecting the USB client device to the USB host device. The USB host device can have means (such as a wireless infrared connection, a wireless radio frequency (RF) connection, a USB cable, or network interface) for communicating with a computer while the USB host device is connected to a USB client device. The USB host device can be a device having a wireless connection to a computer. The USB client device can be a printer. The USB host device can be a network adapter. Preferably, the power supply unit supplies sufficient power for all normal operations of the USB host device. Preferably, the power supply unit is integral with the USB client device.  
         [0028]     The present invention also includes a USB host/client system comprising a USB host device; having a USB port for connection to a USB client device; a USB client device connected via a USB cable to the USB host device; and a power supply unit remote from the USB host device for powering the USB host device through the USB cable connecting the USB client device to the USB host device, wherein the power supply unit supplies sufficient power for all normal operations of the USB host device. The USB host device can be a device having a wireless connection to a computer. The USB client device can be a printer. The USB host device can be a network adapter. Preferably, the USB host device has means (such as wireless infrared connection, a wireless RF connection, a USB cable, or network interface) for communicating with a computer while the USB host device is connected to a USB client device. Preferably, the power supply unit is integral with the USB client device. Preferably, circuitry is included for detecting when the USB host device is connected to the USB client device but is not powered by a power supply in the USB host device, and causing the power supply unit to supply power to the USB host device; and detecting when the USB host device is connected to the USB client device and is powered by a power supply in the USB host device, and causing the power supply unit to not supply power to the USB host device.  
         [0029]     The present invention includes a module for facilitating use of the USB host devices and USB client devices, comprising electronic circuitry to detect an un-powered USB host device connected to a USB client device, the USB host device having a USB VBUS pin; and a power supply unit remote from the USB host device for connection to the USB VBUS pin to power the USB host device and provide the USB client device a proper indication that a powered USB host device has been plugged in. Preferably, this module is integral with the USB client device.  
         [0030]     The present invention includes a method of facilitating use of USB host devices and USB client devices, comprising in or in conjunction with a USB client device, using an additional device or module to detect the presence of a connected but un-powered USB host device having a USB VBUS pin; and applying power to the USB VBUS pin to power up the USB host device and provide the USB client device a proper indication that a powered USB host device has been plugged in.  
         [0031]     In many embodiments of the present invention, the USB client device can be a printer and the USB host device can be a wireless network adapter.  
         [0032]     Preferably the module of the present invention is integral with the USB client device, which is preferably a printer.  
         [0033]     The USB client device of the present invention could be a low-speed device, but preferably is a high/full speed device.  
         [0034]     Most likely, the host device must be modified to accept power from the adapter module of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0035]     For a further understanding of the nature, objects, and advantages of the present invention, reference should be made to the following detailed description, read in conjunction with the following drawings, wherein like numerals denote like elements and wherein:  
         [0036]      FIG. 1  shows a prior art arrangement of a high/full-speed USB client device connected to a USB host device through a USB cable and a low-speed USB client device connected to the USB host device through a USB cable;  
         [0037]      FIG. 2  is a schematic diagram of the prior art showing a high/full-speed USB client device connected to a USB host device through a USB cable and a low-speed USB client device connected to the USB host device through a USB cable;  
         [0038]      FIG. 3  shows an adapter module embodiment of the present invention, connected with USB cables between a printer and a wireless network adapter for the printer;  
         [0039]      FIG. 4  is a schematic diagram showing an adapter module of the preferred embodiment of the present invention, connected with USB cables between a printer and a network adapter (which could be wireless) for the printer;  
         [0040]      FIG. 5  is a schematic diagram showing circuitry which could be used in the detection and power circuit of the adapter module of the present invention; and  
         [0041]      FIG. 6  is a flow chart illustrating the detection circuit logic and power logic of the adapter module of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]     By using an additional device or module  10  (see  FIGS. 3 and 4 ) to detect the presence of a connected but un-powered USB host device, power could be applied to the USB VBUS pin to power the USB host device and provide the USB client device the proper indication that a powered USB host device has been plugged in. As used herein, the term “transceiver” means either a physical layer under USB Specification 2.0 or a transceiver device under USB Specification 1.1.  
         [0043]      FIG. 1  shows a high/full-speed USB client device  22  (a scanner) connected to a USB host device  21  (a personal computer e.g., and, for example, one available for home or office use from Dell Computer Corporation) through a USB cable  24 A and a low-speed USB client device  23  (a mouse) connected to the USB host device through a USB cable  24 B.  
         [0044]      FIG. 2  is a schematic diagram of the prior art showing scanner  22  having a high/full speed USB transceiver  25  with signal line D+  25 A and signal line D−  25 B connected to host PC  21  through USB cable  24 A with a pull-up resistor Rpu connected to the D+ signal line of transceiver  25 . Also connected to host PC  21  is a mouse  23  having a low speed USB transceiver  26  having D+ and D− signal lines  26 A,  26 B connected to PC  21  through USB cable  24 B with pull-up resistor Rpu connected to the D− signal line of transceiver  26 . At host PC  21  is a high/full speed or low speed transceiver  27  with pull-down resistors Rpd connected to each of the D+ and D− signal lines to which transceiver  27  is connected, as well as power supply  29 .  
         [0045]      FIG. 3  shows an adapter module  10  of the preferred embodiment of the present invention, connected with USB cables  24 C and  24 D between a printer  32  (such as Lexmark® Model Z53, Model Z33, or Model Z13) and a wireless network adapter  31  for the printer  32 . In  FIG. 3  host PC  21  includes an infrared transponder IR.  
         [0046]      FIG. 4  is a schematic diagram showing an adapter module  10  illustrative of the present invention.  FIG. 4  shows both a host and a client USB adapter with pull-down and pull-up resistors for a high/full-speed USB client configuration. Adapter module  10  is connected with USB cable  24 C to printer  32  and with USB cable  24 D to external network adapter  31  for the printer  32 . External network adapter  31  includes a high/full speed or low speed USB transceiver  34  having pull-down resistors Rpd connected to signal lines D+ and D−. Printer  32  includes a high/full speed USB transceiver  35  having signal lines D+ and D− with a pull-up resistor Rpu connected to signal line D+. Adapter module  10  includes a 5V power supply  15  and a power and detection circuit  16  communicatively connected to the USB cables  24 C and D.  
         [0047]      FIG. 5  is a schematic diagram illustrating circuitry which could be used in the detection and power circuit of the adapter module  10  of the present invention. Detect logic circuit  40  is communicatively coupled to signal lines D+ and D− and is used to sense the presence of a signal on these lines. Detect logic circuit  40  is also communicatively coupled to a power control circuit  42  which is used to provide power to an unpowered USB host device when connected to adapter module  10 . Power control circuit  42  also controls the operation of switches S 1  and S 2  in signal lines D+ and D− respectively as described with regard to  FIG. 6 . A power supply  15  can also be provided in adapter module  10  and be used to power the unpowered USB host device and the adapter module  10 . Also, provided that the power supply (not shown) in the client device has sufficient capacity, power can be supplied from the USB client device to power the adapter module  10  and the unpowered USB host device  31 .  
         [0048]     The addition of adapter module  10  would detect and isolate the D+/− lines from the client adapter in printer  32  and detect the presence of a plugged in but un-powered host adapter in external network adapter  31 . Once detected, power would be applied to the VBUS pin and the D+/− lines would be connected. This would provide the effect of plugging in a powered host adapter to the client while providing power to the host.  
         [0049]     In order to maintain power to the host device, the detection logic would also look to make sure the host device was still connected. One way to do this would be to detect the Start of Frame (SOF) information that an active USB host sends every one millisecond.  
         [0050]      FIG. 6  illustrates a flow chart of the detect logic and power logic of adapter module  10 . At block  601  the client device is powered on or initialized. At block  603  adapter module  10  then detects a connection signal on either of the signal lines D+ and D−. At block  605  the presence of VBUS power is determined. If a current path from D+ or D − signal to ground exists for some period of time (250 ms, e.g.) and VBUS Power is not present, then, at block  607 , VBUS (5 volts) power is applied to the unpowered host adapter  31 , and, at block  609 , inactivity of the D+ or D− signal lines is monitored by either monitoring the SOF signal from the USB host device or if removal of current path on signal lines D+ or D− is detected. If the signal lines D+ or D− are inactive, VBUS power is removed at block  611 , the adapter module then waits for a disconnect on signal lines D+ and D− at block  613  and then returns to detecting a D+ or D− signal line connection at block  603 . If, at block  605 , VBUS power is present, then the adapter module waits for a disconnect on signal lines D+ and D− at block  613 . The process returns to block  603  monitoring the D+ and D− signal line connections.  
         [0051]     This logic would still allow a powered host to be connected. The detection logic would hold off because of the presence of 5 volts on the VBUS line yet the power logic would still connect the D+/− signal lines using switches S 1  and S 2 , respectively. The detection of VBUS power supplied by either the adapter module  10  or the USB host device  31 , would allow the power logic to close switches S 1  and S 2 .  
         [0052]     The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.