1. Field of the Invention
This invention generally relates to audio electrical devices and, more particularly, to a system and method for detecting the type of headset connected to an audio electrical device.
2. Description of the Related Art
The following discussion is directed to wireless communications devices. However, it should be understood that the discussion applies to other types of electronic devices as well. Wireless communications devices are being developed to perform functions beyond those associated with traditional voice communication. Among those functions is the ability to provide audio signals to a headset plugged into the device. To perform audio functions properly, to manage energy consumption in the wireless device, and to prevent damage to circuitry caused by the application of incompatible signals, the device must be able to distinguish a stereo headset from a different type of accessory, for example, a mono headset, plugged into a device interface port. For example, supplying a stereo signal to a mono headset wastes energy in the device and supplying a mono signal to a stereo headset fails to utilize the features of the headset. At the same time, wireless device users demand smaller and more inexpensive devices with added capabilities, creating in turn, a need to reduce the number and cost of components in the device. An undesirably large number of components are typically used in a wireless device to identify the type of accessory plugged into the device. Unfortunately, increasing the number and complexity of components in a device can limit the size to which the wireless device can be reduced and can add to the cost of producing the wireless device.
It would be advantageous if a wireless communications device could identify the type of headset plugged into the device using a minimal number of relatively simple components.
The present invention addresses identification of a headset plugged into a device audio interface port. The invention recognizes that the device must identify the headset type to provide proper audio signals to the headset. The invention addresses this problem by using a small number of relatively simple components in the device to identify the voltage level associated with a headset type.
Accordingly, a system is provided for identifying a headset type in an electrical device having an audio interface port. The system includes a microcontroller logic unit with an output connected to a test network, the output to supply a test voltage. The test network also is connected to the audio interface port. The test network can include combinations of resistors, capacitors, and switches. A voltage determination sub-system, in one case, an analog-to-digital converter (ADC), has an input connected to the audio interface port and an output to supply a determination signal proportional to a voltage at the audio interface port. The logic unit has an input connected to the voltage determination sub-system output and compares determination signal values with a predetermined threshold value to identify a headset type connected to the audio interface port. In some cases, a digital-to-analog converter (DAC) supplies stereo signals in response to the logic unit identifying a stereo headset.
Additional details of the above-described system and a method for identifying, in an electrical device having an audio interface port, a headset type are provided below.
The system 100 also includes an identification sub-system 116. The identification sub-system 116 has an input connected to the audio interface 104 port on line 114 and an output on line 112 to supply the switch control signal. In general, the identification sub-system 116 determines the voltage on line 114 and distinguishes among accessories or sets of accessories (not shown) connected to line 114 in response to comparing the voltage level on line 114 with a first predetermined threshold value.
A network 106 resistance, say R2, further explained below, and a resistance, say R1, for an accessory connected to the audio interface 104 form a voltage divider for the test voltage. For two resistances, R1 and R2, in series, a voltage divider is formed by applying a voltage V1 to R1. For the voltage divider, a voltage at the node between R1 and R2 is equal to [V1 R2]/[R1+R2]. In system 100, a voltage on line 114, V114=[test voltage][accessory resistance]/[network resistance+accessory resistance]. Thus, the first predetermined threshold value described above can be selected proportional to the V114 associated with a particular accessory or accessories. For example, if a first accessory results in a V114 of 0.5V, and a second accessory above results in a V114 of 0.1V, the first threshold value in the identification sub-system 116 can be selected proportional to a value between 0.5V and 0.1V, say 0.3V, to distinguish between the first and second accessories.
In
It should be understood that the relationship between the second threshold value and voltages on line 114 can be inverted (not shown). In that case, the identification sub-system 116 identifies a stereo headset 118 on the line 114 in response to determining a voltage level on line 114 below the second predetermined threshold value and a mono headset on the line 114 in response to determining a voltage level on line 114 above the second predetermined threshold value.
In some aspects, the system 100 includes a test voltage source 122 and the identification sub-system 116 includes a voltage determination sub-system 124 and a controller 126. The test voltage source 122 has an output connected to the switch 102 input on line 108. The voltage determination sub-system 124 has an input connected to line 114 and an output on line 128 to supply a determination signal responsive to the voltage at the audio interface port 104. The controller 126 has an input on line 128 to accept the determination signal and an output on line 112 to supply the switch control signal. The controller 126 distinguishes between a stereo headset 118 and a mono headset 118 by comparing the determination signal received on line 128 to a third predetermined threshold value. In one aspect, the controller 126 identifies a stereo headset 118 connected to the audio interface port 104 in response to accepting a determination signal with a value above the third predetermined threshold value and a mono headset 118 in response to accepting a determination signal with a value below the third threshold value.
It should be understood that the relationship between the third threshold value and the determination signals on line 128 can be inverted (not shown). Then, the controller 126 identifies a stereo headset 118 on the line 114 in response to accepting a determination signal with a value below the third predetermined threshold value and a mono headset 118 in response to accepting a determination signal with a value above the third threshold value.
In some aspects, the system 100 includes a microcontroller logic unit 130. The microcontroller logic unit 130 includes the switch 102, the test voltage source 122, and the controller 126 and has an input connected to the voltage determination sub-system 124 output on line 128 and a general purpose input/output pin connected to the test network 106 port on line 110. The controller 126 input on line 128 is connected to the logic unit 130 input and the switch 102 output is connected to the logic unit general purpose input/output pin on line 110.
In some aspects, the voltage determination sub-system 124 is an analog-to-digital converter (ADC) 132 with an input connected to line 114 and an output connected to line 128. Typically, the ADC 132 is a “house keeping” ADC (HKADC). HKADCs generally operate at lower resolutions and speeds, which are adequate for the measurements required for the voltage determination sub-system 124 functions.
In some aspects, the switch 208 is a transistor with a terminal connected to capacitor 202 on line 204, a terminal connected to ground 206 on line 210, and a control terminal connected to the logic unit 130 output on line 212. The transistor is enabled in response to accepting the test control signal, creating a signal path between lines 204 and 210. In some aspects, the transistor is a field effect transistor (FET) or a bi-polar junction transistor (BJT). In
Returning to
In some aspects, the system 100 includes a blocking network 148 with a port connected to the DAC 144 output on line 150 and a port connected to line 114. In some aspects, the blocking network 148 includes a capacitor 152 with an end connected to the DAC 144 output on line 150 and an end on line 154 and a resistor 156 with an end connected to the capacitor 152 on line 154 and an end connected to line 114. The blocking network 148 isolates the DAC 144 output from DC and low frequency signals, protecting the DAC 144 from damage such signals could potentially cause.
In some aspects, a Step 301 plugs the headset into the device audio interface port and detects, in the device, the presence of the headset. In some aspects, a Step 316 supplies a stereo audio signal to the connector port. In some aspects, a Step 318 filters DC and low frequency signals. In some aspects, supplying a stereo audio signal to the connector port in Step 316 includes open circuiting the network.
In some aspects, driving a network with the test voltage and dividing the test voltage between a resistance for the network and a resistance for the headset in Step 306 includes using the network to reduce a rate of change for the voltage at the device audio interface port. In some aspects, measuring a divided test voltage in Step 308 includes accepting an analog voltage, converting the analog voltage to a digital signal, and interpreting the digital signal.
In some aspects, identifying a headset type in Step 314 includes identifying a stereo headset for a measured voltage level greater than the threshold value and identifying a mono headset for a measured voltage level less than the threshold value. In some aspects, identifying a headset type in Step 314 includes identifying a stereo headset for a measured voltage level less than the threshold value and identifying a mono headset for a measured voltage level greater than the threshold value.
A system and a method are provided for identifying a headset type in an electrical device having an audio interface port. Examples of the present invention have been enabled with a wireless communications device, audio signals, and a headset. However, it should be understood that the present invention is not limited to wireless communications devices, audio signals, or headsets. The present invention system and method are applicable to any device receiving electrical signals from an external accessory and can be used to identify external accessories other than headsets. For example, the invention could be used to identify Universal Serial Bus (USB) accessories interfacing with a device. The present invention system and method also are applicable to any device making decisions based on the level of electrical signals from an external accessory. Other variations and embodiments of the present invention will occur to those skilled in the art.
Although the invention has been described with reference to particular embodiments, the description is only an example of the invention's application and should not be taken as a limitation. Consequently, various adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as encompassed by the following claims.
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Number | Date | Country | |
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20050053243 A1 | Mar 2005 | US |