Abstract:
This invention is a single wire interface communication system whereby a phone having internal charging circuitry communicates the charging status of the battery attached to the phone by varying the duty cycle of a pulse with a predetermined period across the single wire interface. In a preferred embodiment, the predetermined pulse of time T, where T is 1 second, is divided into N divisions, where N equals 10. A duty cycle high for time T/N and low for time 9T/N represents a first charging state; a duty cycle high for time 2T/N and low for time 8T/N corresponds to a second charging state; and so on. The system allows for information to be transmitted across a single wire, thereby freeing data connections for other accessories.

Description:
TECHNICAL FIELD 
     This invention relates generally to chargers for communications devices. More specifically, this invention relates to a single wire communication method for transmission of charging status from a phone to a charger. 
     BACKGROUND 
     In the past, cellular phones have been used as communication devices that transmit analog acoustic signals, i.e. voice and sound, from a handset to a cellular network. When a person speaks into the phone, the sound waves generated by the mouth are received by a microphone and converted into analog electrical signals, or waves. These electrical waves are then transmitted from the phone to a cellular tower, where they pass through the cellular network and are then routed to the recipient&#39;s phone. The electrical waves are then converted back into sound through a loud speaker. In this fashion, analog phones provide effective, reliable transmission of sound. 
     The advent of digital phones brought about a change in the transmission process. In a digital phone, the sound waves received by the microphone are encoded into a specific series of zeroes and ones called a “digital word”. This encoding takes place in an “analog to digital” converter. The zeroes and ones are then sent to the cellular network in the form of radio waves, where they again pass through the tower and are sent to the recipient&#39;s phone. There they are decoded by a “digital to analog” converter. They then are converted to sound through the loud speaker. 
     Digital phones offer several advantages over their analog counterparts. First, digital signals are virtually immune to static noise. Static takes the form of analog waves that look to the phone like normal phone calls. In a digital phone, however, the phone call looks very different from the static. The phone is thus able to filter out the noise. 
     Second, cellular networks can fit many more digital signals into a wire than analog signals. Again, due to the sophisticated filtering in digital systems, a phone can easily distinguish it&#39;s digital call from that intended for another phone. 
     Finally, as computers also communicate with ones and zeroes, digital phones are able to receive more than just sound. For example, digital phones can receive pages, caller identification data, internet information, text, pictures and other information. The i1000 phone manufactured by Motorola, for instance, can receive text pages, voice mail, and caller identification data in addition to phone calls! 
     While these additional features of digital phones are great for the end user, they present some major obstacles for the battery charger designer. For example, chargers for some phones include charging algorithms which ramp and taper the voltage and current to charge a battery. Chargers for other phones, however, supply basic voltage to the phone, while charging circuitry inside the phone ramps and tapers the voltage and current. For these phones, where the charging circuitry located inside the phone, the phone must communicate it&#39;s charging state, i.e. one quarter charged, half charged, etc., to the charger. This information is needed by the charger because the charger lights an indicator depending -upon the charge state. For example, a green light on the charger might indicate a fully charged battery while a red light might indicate a charging battery. 
     Traditionally, this communication occurred through a data connector located on the bottom of the phone. When the phone was in the charger, the charger data connector mated with the phone data connector. The state of charge was communicated digitally across this interface. With the advent of digital communication features, many phones now come with accessories like global positioning systems that connect to the phone&#39;s data connector. If such an accessory is connected to the phone when the phone is inserted in the charger, the charger can no longer use this port for communicating charging information. 
     There is thus a need for an improved, simplified charging status indication means in telephone/charger systems. 
     SUMMARY OF THE INVENTION 
     This invention is a method by which the charging status of a battery can be transmitted from a microprocessor in a phone or radio to a charger across a single wire interface. The communication is accomplished by modulating the duty cycle of logic “high” signals across a predetermined pulse period. The pulse period is subdivided into N increments. By way of an example, if N=10 and the pulse width is 1 millisecond, each {fraction (1/10)} of a millisecond is one division. A word then corresponds to a specific relationship of the number of divisions that the line is high, versus the number of divisions the lines is low. In other words, when the logic signal on the one wire interface is high for one-tenth of a pulse, this may correspond to a battery state of 0% to 30% charged, which should cause a red LED on a charger to illuminate. In another case, if the line is high for two-tenths of a pulse, this may tell the charger that the battery is between 31% and 60% charged, causing the charger to light a yellow LED. This invention is for use in systems where the charger acts as a slave to a phone or radio that has its own charging circuitry. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a preferred embodiment of the hardware used to implement the invention. 
     FIGS. 2A,  2 B,  2 C,  2 D,  2 E,  2 F,  2 G are illustrates a preferred embodiment of the duty cycle waveforms used for communication. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Many modern phones include internal battery charging circuitry. The phone includes charging circuitry in order to accept a wider variety of charging devices. For example, when a phone includes charging circuitry, either a power supply—which supplies a constant voltage and current—or a charger—which supplies a specific battery charging tapered, ramped, or modulated current—can be used to charge the battery. When a power supply is connected, the internal charging circuitry works to ramp, taper, or modulate the current to charger the battery. When a charger is connected, either the charging circuitry of the charger or the charging circuitry of the phone remains passive. The other circuit then ramps, tapers and modulates the current to charge the battery. 
     When a phone does not include charging circuitry, the only device that may be connected to the phone to charge the battery is a charger. As batteries are most efficiently charged with specific charging algorithms, if a power supply—with constant voltage and current—were connected, the phone would not charge the battery. This is true because if the voltage or current coming from the power supply were too great, reliability and performance of the battery could be compromised. 
     When engineers build a charger specifically for a phone with internal charging circuitry, they often eliminate the chargers charging circuitry to eliminate redundancy and reduce cost. In other words, as the engineer knows that the phone will be equipped with charging circuitry, he knows not to add such circuitry to the phone pocket of the charger. Thus, the engineer generally designs in a direct connection from the power supply to the phone pocket of the charger. This allows the phone to sit in a desk top charging stand while being connected directly to a power supply. 
     Referring now to FIG. 1, a charging system  1  with a passive desk-top stand  100  is illustrated therein. In this system  1 , a charger  100  with a microprocessor  101  is provided which includes two pockets  110 , 111  for charging batteries. The first pocket  110  is for charging a phone  200  with a battery  300  attached. The second pocket  111  is for charging a battery  400  by itself. The front pocket  110  provides a first set of contacts  114 , 106 , 107  for providing an electrical connection between the phone  200  and the charger  100 . Similarly, a second set of contacts  108 , 109  are provided for connecting the an additional battery  400  to the charger  100 . 
     The charger  100  is equipped with a microprocessor  101  which ramps, tapers, and modulates the voltage and current supplied by the power supply  10  for the second pocket  111 . This is accomplished by driving a pass element  115  with a control line  114 . Additionally, the microprocessor  101  drives a first indicator light emitting diode  112 , “LED”, through a first LED control line  113 . This first LED  112  indicates the status of charge of the battery  301  in the front pocket  110 . The microprocessor also drives a second LED  116 , through a second LED control line  117 . The second LED  116  indicates the state of charge for the spare battery  400  in the rear pocket  111 . 
     In a preferred embodiment, the LEDs  112 , 116  emit different colors and patterns to indicate states of charge. For simplicity, we will use the first LED  112  and the battery  301  in the front pocket  110  to illustrate this function. The same function can be applied to the second LED  116  to indicate the state of charge of the spare battery  400  in the rear pocket. 
     When the battery  301  is between 0% and 30% charged, the LED  112  is driven to a solid red state. When the battery  301  is 31% to 60% charged, the LED  112  is driven yellow. When the battery  301  is 61% to 90% charged, the LED  112  is driven to a flashing green state. When the battery  301  is 91% to 100% charged, the LED  112  is driven to a solid green state. If the battery  301  is too hot or to cold, and thus the charger  100  is in stand-by mode while waiting for the battery  301  to cool, the LED  112  is driven to a flashing yellow state. If there is an error in charging, the LED  112  is driven to a flashing red state. If no battery is in the front pocket  110 , the LED  112  is turned off. 
     In the front pocket  110 , charging is controlled by the charging circuitry  201  in the phone  200 , as a direct connection  105  from the power supply  10  is provided to the first set of contacts  107 , 114 . The charging circuitry  201  in the phone  200  ramps, tapers and modulates the voltage and current being delivered to the battery  300  attached to the phone  200 . While the charger  100  is passive, the LED  112  still needs to indicate the state of charge for the battery  300  attached to the phone  200 . 
     The invention is a single wire interface  102  by which the charging circuitry  201  in the phone  200  communicates the battery  300  state of charge to the microprocessor  101  in the charger  100 . Once the microprocessor  101  in the charger  100  receives this information, it  101  can then illuminate the LED  116  correspondingly. The means by which the invention is implemented include a single wire bus  102  which connects the charging circuitry  201  in the phone  200  to the charger microprocessor  101 . In the charger  100 , this line  102  is pulled up to +5V  104  by a pull-up resistor  103 . The single wire connection  102  between the phone  200  and charger  100  is made through a single wire contact  106  located in the front pocket  110 . 
     In accordance with the invention, the microprocessor  101  in the charger  100  looks for data across the single wire interface  102  in N divisions across a period T. By way of an example, we will assume that N=10 and T=1 second. Note that a corresponding period of N is T/N, or 100 milliseconds. When no phone is in the front pocket  110 , the pull-up resistor  103  keeps the single wire interface  102  constantly high (pulled up to +5V  104 ). The microprocessor  101  in the charger  100  thus sees the interface  102  at +5V  104  for the entire 1 second pulse and thereby knows that no phone is in the front pocket  110 . The LED  112  is correspondingly driven to an off state. 
     Once a phone  200  is placed in the front pocket  110 , however, the charging circuitry  201  in the phone  200  has the ability to drive the single wire interface  102  to a low state. When the single wire  102  transitions from a high to a low state, the microprocessor  101  in the charger  100  knows that a phone  200  has been placed in the pocket  110 . The microprocessor  101  in the charger  100  then polls the single wire interface  102  once every 100 milliseconds, in wait for data to be transmitted. 
     The charging circuitry  201  in the phone  200  can then communicate the charging status of the battery  300  to the charger  100  by varying the duty cycle in multiples of N divisions across each 100 millisecond pulse. For example, if the pulse was high for a period of 1N, or 100 milliseconds, and low for 9N, or 900 milliseconds, this may correspond to a first charging state. Similarly a high state of 2N with a low state of 8N would correspond to a second charging state and so on. 
     Referring now to FIG. 2, illustrated therein are several varying duty cycles based upon a pulse with period ION. The pulse that is constantly in a low state is not shown, as this pulse transmits no charging information. As both the charger microprocessor and battery charging circuitry in the phone include real time clocks, they are able to discern the varying duty cycles transmitted across the single wire interface without needing additional clocking data. 
     The communication algorithm may best be explained by an example. In the lab, a charger and phone were built so as to recognize the following pulse duty cycles: First, a pulse where the single wire interface is high for a period 10N, illustrated in FIG.  2 (G) indicates that there is no phone in the pocket and that the LED should be in the off state. A pulse that is high for a time N and then low for a time 9N, illustrated in FIG.  2 (A), indicates a battery that is between 0% and 30% charged, which should cause the LED to be in a constant red state. A pulse that is high for a time 2N and then low for a time 8N, illustrated in FIG.  2 (B), indicates a battery that is between 31% and 60% charged, which should cause the LED to be in a constant yellow state. A pulse that is high for a time 3N and then low for a time 7N, illustrated in FIG.  2 (C), indicates a battery that is between 61% and 90% charged, which should cause the LED to be in a flashing green state. A pulse that is high for a time 4N and then low for a time 6N, illustrated in FIG.  2 (D), indicates a battery that is between 91% and 100% charged, which should cause the LED to be in a constant green state. A pulse that is high for a time 5N and then low for a time 5N, illustrated in FIG.  2 (E), indicates a battery that is too hot or too cold, which should cause the LED to be in a flashing yellow state. A pulse that is high for a time 6N and then low for a time 4N, illustrated by FIG.  2 (F), indicates an error, which should cause the LED to be in a constant red state. A pulse that is high for more than 7N divisions indicates that no battery is present. In this fashion, the battery may communicate seven different states of charge across a single wire by varying the duty cycle of a pulse with period T and N divisions. 
     While the preferred embodiments of the invention have been illustrated and described, it is clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims. For example, while the invention has been described as a pulse with period T with 10 divisions, more information could be added by dividing the pulse into a larger number of divisions. A pulse with period T and 200 divisions, for instance, could communicate 16 different charging states if so desired.