Abstract:
A radio frequency identification (RFID) tag reader. The tag reader includes a power detection circuit operable to detect power from a plurality of different power sources, and a controller for operating the radio frequency identification tag reader at a power consumption level commensurate with a detected power source.

Description:
BACKGROUND OF THE INVENTION 
     It would be desirable to provide a radio frequency identification (RFID) tag reader capable of receiving power from a plurality of different power sources. 
     SUMMARY OF THE INVENTION 
     A radio frequency identification (RFID) tag reader is disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a system including an RFID tag reader; and 
         FIG. 2 . is a flow chart illustrating an example mode of operation of the RFID tag reader. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , an example embodiment of a radio frequency identification (RFID) tag reading system  10  includes RFID reader  12 . 
     RFID reader  12  obtains power from a plurality of different power sources. One such power source includes Power over Ethernet (PoE). The current PoE standard (IEEE 802.3af) allows up to thirteen watts of power to be delivered to an end device. Use of PoE as a data communication and power source simplifies wiring, facilitates easier remote hard resets during servicing, and facilitates the use of a centralized uninterruptible power supply (UPS)  52 . 
     Other power sources may includes local power sources, such as battery  54 , or standard line voltage via external power adapter  56 . 
     Example RFID reader  12  includes PoE Ethernet interface  20 , power detect circuit  24 , adjustable RF transceiver  28 , antenna  30 , and controller  32 . 
     PoE Ethernet interface  20  couples RFID reader  12  to a network. For example, PoE Ethernet interface  20  may be coupled to a PoE capable network switch  42  via a network cable  44 . Network switch  42  may be coupled to a network adapter  46  in computer  50  via network cable  48 . While coupled to the network, RFID reader  12  not only receives power, but also transfers RFID tag data to computer  50  and receives instructions from computer  50 . Power to the PoE capable network switch  42  may be supplied by standard line voltage, from an uninterruptible power supply  52 , or both. 
     Power detect circuit  24  detects whether the RFID reader  12  is receiving power from the network via PoE Ethernet interface  20 , from a local power such as battery  54 , or from a standard line voltage via external power adapter  56 . 
     Adjustable RF transceiver  28  transmits a signal for interrogating an RFID tag through antenna  30  and receives a response signal from the RFID tag through antenna  30 . The power of the transmitted signal is dictated to adjustable RF transceiver  28  by controller  32 , depending on how RFID tag reader  12  is receiving power. 
     Controller  32  controls operation of RFID tag reader  12 . In an example mode of operation, controller  32  determines whether RFID tag reader  12  operates in a Full Power State or a Reduced Power State, as defined below. 
     RFID reader  12  may further include USB interface  34 , serial port  36 , diagnostic lights  38 , and audible indicator  40 . 
     USB interface  34  provides the option of coupling RFID tag reader  12  to a USB port of a computer, such as computer  50 . Serial port  36  provides another option for coupling RFID tag reader  12  to a computer, and may include an RS-232 serial port. 
     Diagnostic lights  38  and audible indicator  40  provide visual and aural indications to a user of RFID tag reader  12  during operation. 
     Example RFID reader  12  operates in either of two power states: 
     1. Full Power State—RFID tag reader  12  operates with a normal transmission range, tag detection capability, and data transfer rate. When on, diagnostic lights  38  are full bright, and audible indicator  40  is full volume. 
     2. Reduced Power State—RFID tag reader  12  operates with a diminished transmission range, tag detection capability, and data transfer rate. When on, diagnostic lights  38  are dim and audible indicator  40  is reduced in volume. 
     Controller  32  may boot up in the second Reduced Power State, assuming the only available source of power is PoE from PoE Ethernet interface  20  or from battery  54 . In this second Reduced Power State, controller  32  decreases RF power from adjustable RF transceiver  28 . Controller  32  may implement further power saving measures while operating in this state, including reducing processor speed, reducing the duty cycle of adjustable RF transceiver  28 , disabling or dimming operation of diagnostic lights  38 , disabling or reducing operation of audible indicators  40 , and disabling unused interfaces, such as USB interface  34  and serial port  36 . 
     After booting up, controller  32  determines from power detect circuit  24  the available sources of power. If power is available from external power adapter  56 , the controller  32  transitions RFID reader  12  to the first Full Power State. In this first Full Power State, controller  32  increases RF power from adjustable RF transceiver  28 . Controller  32  may further increase processor speed, increase the duty cycle of adjustable RF transceiver  28 , enable full brightness operation of diagnostic lights  38 , enable full operation of audible indicators  40 , and enable all interfaces, such as USB interface  34  and serial port  36 . 
     If controller  32  transitions RFID tag reader  12  to the first Full Power State and then later detects from power detect circuit  24  that external power adapter  56  is no longer providing power, controller  32  responds in a reverse fashion by transitioning RFID tag reader  12  back to the second Reduced Power State. 
     Turning now to  FIG. 2 , an example mode of operation is illustrated beginning with START  60 . 
     In step  62 , controller  32  boots up in the default second Reduced power State. 
     In step  66 , controller  32  waits for a signal from power detect circuit  24 . If controller  32  determines that power is available from external power adapter  56 , operation proceeds to step  68 . Otherwise, operation returns to step  66 . 
     In step  68 , controller  32  transitions RFID reader  12  to the first Full Power State. 
     In step  72 , controller  32  monitors for loss of power from external power adapter  56 . If power is no longer available from external power adapter  56 , operation proceeds to step  74 . Otherwise, operation returns to step  72 . 
     In step  74 , controller  32  transitions RFID tag reader  12  to the second Reduced Power State and then returns to step  66 . 
     Although particular reference has been made to certain embodiments, variations and modifications are also envisioned within the spirit and scope of the following claims.