Accessory communication over power pins

Abstract

Simplified interfaces for charging and communication between accessories and docking stations. One example may provide an interface for charging and communication between an accessory and docking station where data and a charging voltage are provided over the same pins. An accessory may determine that it is in a powered docking station by receiving a charging voltage. The accessory may determine that it is in an unpowered docking station by providing a voltage to the unpowered docking station, where the unpowered docking station uses the voltage to power an oscillator. The oscillator signal may be received by the accessory, which may use the presence of the signal to determine that it is in an unpowered docking station.

What is claimed is: 
     
         1 . Communications circuitry for transmitting data between a docking station and a plurality of accessories, the communications circuitry comprising:
 an oscillator to generate a waveform;   an output driver having an input coupled to an output of the oscillator and having an enable input; and   a first microcontroller coupled to the enable input of the output driver to enable or disable the output driver;   wherein the first microcontroller enables the output driver for a first bit-time to provide a bit having a first polarity, and wherein the first microcontroller disables the output driver for a second bit-time to provide a bit having a second polarity.   
     
     
         2 . The communications circuitry of  claim 1  wherein the first bit time is equal to the second bit time. 
     
     
         3 . The communications circuitry of  claim 1  wherein the oscillator generates an intermediate-frequency waveform. 
     
     
         4 . The communications circuitry of  claim 3  wherein the intermediate frequency is spread-spectrum modulated. 
     
     
         5 . The communications circuitry of  claim 1  further comprising:
 an envelope detector to receive the waveform; and 
 a second microcontroller coupled to the envelope detector to determine whether envelope detector receives a bit having a first polarity or a bit having a second polarity. 
 
     
     
         6 . The communications circuitry of  claim 5  wherein the oscillator, output driver, and first microcontroller are located on the docking station and the envelope detector and second microcontroller is located on one the plurality of accessories. 
     
     
         7 . The communications circuitry of  claim 5  wherein the oscillator, output driver, and first microcontroller are located on one of the plurality of accessories and the envelope detector and second microcontroller is located on the docking station. 
     
     
         8 . The communications circuitry of  claim 5  wherein each of the plurality of accessories and the docking station comprises an oscillator, an output driver, a microcontroller, and an envelope detector. 
     
     
         9 . A method of transmitting data between an accessory and a docking station, the method comprising:
 generating an intermediate-frequency signal;   providing a bit having a first polarity by modulating a first voltage with the intermediate frequency signal for a first bit-time; and   providing a bit having a second polarity by not modulating the first voltage with the intermediate frequency signal for a second bit-time.   
     
     
         10 . The method of  claim 9  wherein the first voltage is a charging voltage provided by the docking station to the accessory. 
     
     
         11 . The method of  claim 9  wherein the intermediate frequency is spread-spectrum modulated. 
     
     
         12 . The method of  claim 9  wherein the docking station transmits data using a first intermediate frequency signal at a first frequency, and the accessory transmits data using a second intermediate frequency signal at a second frequency. 
     
     
         13 . The method of  claim 9  wherein the accessory and docking station communicate using full-duplex communication. 
     
     
         14 . The method of  claim 9  wherein the docking station may communicate with a second accessory. 
     
     
         15 . The method of  claim 14  wherein the accessory and the second accessory may communicate via the docking station. 
     
     
         16 . The method of  claim 9  wherein the first bit time is equal to the second bit time.