Abstract:
Systems, methods, and media for providing power to an HDMI source are provided. In accordance with some implementations, methods for providing power to an HDMI source are provided, the methods comprising: providing an AC signal to an HPD line of an HDMI port; determining that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connecting a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generated using a clock output. In some implementations, the methods further comprise integrating the clock output to provide the AC signal. In some implementations, the methods further comprise switching the frequency of the AC signal.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/014,633, filed Jun. 19, 2014, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    With recent advances in video and graphics rendering and communications has come source media devices (hereinafter, each an “HDMI source”) that are capable of plugging into an HDMI port of a sink media device (hereinafter, an “HDMI sink”) such as a television or monitor. 
         [0003]    Currently, simple HDMI sources use external power supplies to provide power to those sources because the HDMI specification does not provide for an HDMI sink (such as a television) to provide power to the HDMI source through its HDMI connector. Avoiding using an external power supply may be desirable for a variety of reasons, such as cost and ease of use. 
       SUMMARY 
       [0004]    Systems, methods, and media for providing power to an HDMI source are provided. In accordance with some implementations, methods for providing power to an HDMI source are provided, the methods comprising: providing an AC signal to an HPD line of an HDMI port; determining that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connecting a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generated using a clock output. In some implementations, the methods further comprise integrating the clock output to provide the AC signal. In some implementations, the methods further comprise switching the frequency of the AC signal. In implementations, determining that an L-C circuit is present on the HPD line comprises determining whether the AC signal is resonating in the L-C circuit. In some implementations, the methods further comprise: detecting a value of an HPD line of an HDMI sink; and providing the value to an HPD line of an HDMI source. In some implementation, the methods further comprise: determining that an L-C circuit is not present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is not present on the HPD line, disconnecting a power source from an HDMI 5V line of the HDMI port. 
         [0005]    In accordance with some implementations, circuits for providing power to an HDMI source are provided, the circuits comprising: a microcontroller configured to: provide an AC signal to an HPD line of an HDMI port; determine that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connect a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generating using a clock output of the microcontroller. In some implementations, the circuits further comprise an integrator coupled to the clock output which integrates to the clock output to provide the AC signal. In some implementations, the microcontroller also switches the frequency of the AC signal. In some implementations, determining that an L-C circuit is present on the HPD line comprises determining whether the AC signal is resonating in the L-C circuit. In some implementations, the microcontroller also: detects a value of an HPD line of an HDMI sink; and provides the value to an HPD line of an HDMI source. In some implementations, the microcontroller also: determines that an L-C circuit is not present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is not present on the HPD line, disconnects a power source from an HDMI 5V line of the HDMI port. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an example of a block diagram of hardware for detecting an HDMI source and providing power to the HDMI source in accordance with some implementations. 
           [0007]      FIG. 2  is an example of a schematic diagram of a circuit for detecting an HDMI source and providing power to the HDMI source in accordance with some implementations. 
           [0008]      FIG. 3  is an example of a more detailed schematic diagram of a circuit for detecting an HDMI source and providing power to the HDMI source in accordance with some implementations. 
           [0009]      FIGS. 4A-4C  together show an example of instructions that can be executed in a microcontroller (or other suitable device) for detecting an HDMI source and providing power to the HDMI source in accordance with some implementations. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In accordance with some implementations, mechanisms are provided for detecting if an HDMI source is connected to an HDMI port and, if yes, providing power through the HDMI port (e.g., using pin  18  of the port&#39;s HDMI connector, which is normally used by a TV to detect the presence of an HDMI source). 
         [0011]    An example 100 of a mechanism in accordance with some implementations is shown in  FIG. 1 . As illustrated, mechanism  100  can be implemented as a detection module  102  that is present between an HDMI sink  104  and an HDMI source  106 . In some implementations, the detection module uses a presence line  110  (e.g., an “HPD” line) of a port  108  to detect the presence of the HDMI source by applying a low voltage stimulus (e.g., which may be harmless to an unpowered source) to determine if a resonant L-C circuit  112  of the HDMI source can be detected. When the resonant L-C circuit of the HDMI source has been detected, the detection module may then apply a supply voltage (e.g., a 5V supply voltage via a “permanent 5V” line  114 ) to a supply voltage line  116  (e.g., an “HDMI 5V” line). The sink in turn may set presence line  110  (e.g., the “HPD” line) active high and the detection module may then propagate the active high signal to the source. 
         [0012]    Although detection module  102  of  FIG. 1  is illustrated as being located between a port of HDMI source  106  and HDMI sink  104 , the detection module can be integrated with or can be part of HDMI sink  104  in some implementations so that the port of the HDMI sink is port  108  in some implementations. 
         [0013]    The detection module may then continuously or periodically probe presence line  110  (e.g., the “HPD” line) to detect the removal of the HDMI source, in which case the detection module may disconnect the supply voltage (e.g., from the “permanent 5V” line) from supply voltage line  116  (e.g., the “HDMI 5V” line). 
         [0014]      FIG. 2  shows an example of an analog front end of a detection circuit that is part of an HDMI sink in area  202  and an example of a resonant L-C circuit to be detected in area  204 , in accordance with some implementations. 
         [0015]    The voltage sources V 1  and V 2  in  FIG. 2  represent general purpose outputs (GPOs) of a microcontroller (or other suitable device(s)) and the active low signal OEMDET# can be used to inform the microcontroller (or other suitable device(s)) when the L-C circuit has been detected. 
         [0016]    The voltage source VCC represents a 3.3V power supply (or any other suitable power supply) of the analog front end (which can also be used to power a microcontroller (or other suitable device(s)) (not shown) if desired). 
         [0017]    The HDMI sink detects the HDMI source by detecting the presence of a resonant L 1 -C 3  circuit in the HDMI source. The resonant frequency can be determined by L 1  and the equivalent capacitance (Ceq) of C 1 , C 2 , and C 3  in series (e.g., as shown in the example of  FIG. 2 , L 1  can be 100 μH, Ceq can be 4.76 nF, and the resonant frequency can be 231 kHz, in some implementations). In this example, when the HDMI source is not connected, the waveform on the HPD line can be triangular at 231 kHz with a peak-peak value of 340 mV centered around 0V. This signal can be generated by driving the integrator circuit R 1 -C 1  with a 0V-3.3V 231 kHz square wave from the GPO V 1 . 
         [0018]    When the HDMI source is connected, the circuit in the example of  FIG. 2  resonates at 231 kHz and the amplitude of the waveform on HPD line is a sine wave with a peak-peak amplitude of: 
         [0000]    
       
         
           
             
               
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         [0000]    which is the 1st harmonic of a unity square wave. 
         [0019]    It is assumed in the above calculations that (i) the serial resistance R S  of the inductor is 2052, which takes into account the DC resistance, the core loss at 231 kHz and skin effect, and (ii) C 3 &gt;&gt;(C 1 ·C 2 )/(C 1 +C 2 ). 
         [0020]    As shown, this signal is AC coupled by C 4  to the 350 mV DC bias of Q 1  and turns on Q 1  during the positive phase of the waveform (350 mV+898 mV/2=799 mV). The R 7 -C 5  circuit on the collector of Q 1  filters the active low signal OEMDET# which instructs the microcontroller (or other suitable device) to apply HDMI 5V to the HDMI source (e.g., as shown in  FIG. 1 ). 
         [0021]    Because the detection signal is AC coupled to Q 1 , detection can be performed when the HPD line is high or low (as driven by V 2  at 0 or 3.3V, for example); thus, the detection can be performed periodically to detect the removal of the HDMI source as well. 
         [0022]    Although not shown in  FIG. 2 , any suitable circuit for connecting and disconnecting a supply voltage (e.g., a 5V voltage) from the HDMI sink to the HDMI source under the control of the microcontroller (or other suitable device) can be provided in some implementations. For example, a switch controlled by the microcontroller can be used to connect and disconnect the supply voltage from the HDMI sink to the HDMI source. 
         [0023]    Another example 300 of a circuit for implementing some implementations of mechanisms disclosed herein is illustrated in  FIG. 3 . As shown, circuit  300  includes many of the same components as shown in  FIG. 2 . For example, the transistor, resistors, and capacitors shown in area  202  of  FIG. 2  are also shown in  FIG. 3 . The voltage sources V 1  and V 2  of  FIG. 2  are shown in  FIG. 3  by two GPOs of microcontroller  308  (which can be any suitable device (e.g., a hardware processor for controlling the operation of the mechanisms described herein) such as an MSP430G2001IPW14 microcontroller available from Texas Instruments of Dallas, Tex.). The voltage source VCC of  FIG. 2  is shown in  FIG. 3  by a 3.3V regulator  310  (which can be any suitable device for providing power, such as a TLV70033 regulator available from Texas Instruments of Dallas, Tex.). Regulator  310  can receive power at its input from a permanent 5V source  302  (e.g., a USB port of a TV) or the HDMI 5V line between the source HDMI receptacle  304  and the sink HDMI receptacle  306 , via diodes D 1  (which can be any suitable diodes). A switch which provides power between the permanent 5V line and the HDMI 5V line (described above in connection with  FIG. 1 ) can be provided by controllable switch  510  (which can be any suitable device for controlling a connection between a source of power and the HDMI 5V line, such as a TPS2051 switch available from Texas Instruments of Dallas, Tex.). 
         [0024]    In accordance with some implementations, instructions that can be executed in a microcontroller (or other suitable device) in conjunction with the circuits of  FIGS. 2 and 3  are illustrated in  FIGS. 4A, 4B, and 4C . 
         [0025]    As shown, the instructions at lines  01 - 06  define a state variable as having one of three possible states (“idle,” “normal source,” and “power-over-HDMI source”) and set the state&#39;s initial value. 
         [0026]    The instructions at lines  08 - 16  turn ON or OFF a GPO that controls a switch that connects the permanent 5V line to the HDMI 5V line. 
         [0027]    The instructions at lines  18 - 24  set the value on the HPD line at the source connector as either a 0 or a 1. 
         [0028]    The instructions at lines  26 - 28  determine a state of the HPD line at the sink connector. 
         [0029]    The instructions at lines  30 - 33  return whether 5V is at the output of the switch (i.e., at the HDMI 5V line between the sink and the source). 
         [0030]    The instructions at lines  34 - 36  check the signal of the collector of transistor Q 1  to determine whether an L-C circuit is detected. 
         [0031]    The instructions at lines  38 - 51  apply a clock signal at different frequencies (e.g., 231 kHz, 231 kHz+3%, 231 kHz−3%, 231 kHz+6%, 231 kHz−6%, . . . , 231 kHz+15%, 231 kHz−15%, and/or any other suitable frequencies) to the HPD line to determine whether the L-C circuit can be detected. As shown in these instructions, the clock signal can be provided at different frequencies to account for tolerances in the characteristics of the inductor and the capacitor making up the L-C circuit. 
         [0032]    The instructions at lines  52 - 80  form the main procedure of the instructions and execute an infinite loop that perform three different groups of steps based on whether the process is in one of the three difference states. 
         [0033]    As shown, if the state is the idle state, the process:
       a. turns off the 5V switch;   b. sets the HPD line at the source to match the HPD line at the sink;   c. if 5V is on the HDMI 5V line, sets the state to the normal source state;   d. if 5V is not on the HDMI 5V line and the HPD line is connected to an L-C circuit, sets the state to a power-over-HDMI source state; and   e. if 5V is not on the HDMI 5V line and the HPD line is not connected to an L-C circuit, delays the process by one second and leaves the state in the idle state.       
 
         [0039]    If the state is in the normal source state, the process:
       a. turns off the 5V switch;   b. sets the HPD line at the source to match the HPD line at the sink; and   c. if the HDMI 5V line is not at 5V, sets the state to the idle state.       
 
         [0043]    If the state is in the power-over-HDMI source state, the process:
       a. turns on the 5V switch;   b. sets the HPD line at the source to match the HPD line at the sink;   c. if the HPD line is not connected to an L-C circuit, sets the state to an idle state; and   d. if the HPD line is connected to an L-C circuit, delays the process by one second and leaves the state in the power-over-HDMI source state.       
 
         [0048]    In some implementations, any suitable computer readable media can be used for storing instructions for performing the processes described herein. For example, in some implementations, computer readable media can be transitory or non-transitory. For example, non-transitory computer readable media can include media such as magnetic media (such as hard disks, floppy disks, etc.), optical media (such as compact discs, digital video discs, Blu-ray discs, etc.), semiconductor media (such as flash memory, electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), etc.), any suitable media that is not fleeting or devoid of any semblance of permanence during transmission, and/or any suitable tangible media. As another example, transitory computer readable media can include signals on networks, in wires, conductors, optical fibers, circuits, any suitable media that is fleeting and devoid of any semblance of permanence during transmission, and/or any suitable intangible media. 
         [0049]    The provision of the examples described herein (as well as clauses phrased as “such as,” “e.g.,” “including,” and the like) should not be interpreted as limiting the claimed subject matter to the specific examples; rather, the examples are intended to illustrate only some of many possible aspects. 
         [0050]    Although the disclosed subject matter has been described and illustrated in the foregoing illustrative implementations, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the disclosed subject matter can be made without departing from the spirit and scope of the disclosed subject matter, which is limited only by the claims that follow. Features of the disclosed implementations can be combined and rearranged in various ways.