WO2015179968A1

WO2015179968A1 - Apparatus, methods and systems for monitoring physiological parameters with portable electronic devices

Info

Publication number: WO2015179968A1
Application number: PCT/CA2015/050454
Authority: WO
Inventors: Behnam MOLAVI; Tso CHEN
Original assignee: Lionsgate Technologies, Inc.
Priority date: 2014-05-30
Filing date: 2015-05-20
Publication date: 2015-12-03

Abstract

The present disclosure provides apparatus for connecting one or more external sensors to a computing device. The apparatus comprises a digital input/output port configured to connect to a corresponding digital input/output port of the computing device, an analog audio interface comprising a plurality of contacts connectable to the one or more external sensors;, an audio processing unit comprising a digital-to-analog converter (DAC) and an analog-to- digital converter (ADC), a digital communication protocol interface, the audio processing unit operably connected to the digital input/output port, and, signal conditioning circuitry connected between the audio processing unit and the analog audio interface.

Description

APPARATUS. METHODS AND SYSTEMS FOR MONITORING PHYSIOLOGICAL

PARAMETERS WITH PORTABLE ELECTRONIC DEVICES

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from U.S. Provisional Patent Application No.

62/005,418 filed May 30, 2014 and entitled APPARATUS, METHODS AND SYSTEMS FOR MONITORING PHYSIOLOGICAL PARAMETERS WITH PORTABLE ELECTRONIC DEVICES. For purposes of the United States, this application claims the benefit under 35 U.S.C. §1 19 of United States provisional patent application No. 62/005,418, filed May 30, 2014 and entitled APPARATUS, METHODS AND SYSTEMS FOR MONITORING

PHYSIOLOGICAL PARAMETERS WITH PORTABLE ELECTRONIC DEVICES, which is hereby incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

[0002] The present disclosure relates generally to determining physiological parameters of a patient. More particularly, the present disclosure relates to systems, methods and related apparatus for determining physiological parameters with sensors coupled to audio interfaces of electronic devices.

BACKGROUND OF THE INVENTION

[0003] Conventional pulse oximeters, thermometers, blood pressure measurement devices, spirometers, perineometers, ECGs, EEGs, and other devices for measuring physiological parameters are typically standalone units. Standalone electronic devices for measuring physiological parameters usually contain a power source, a microcontroller, local storage, and a custom display mechanism along with the basic circuit needed to perform the sensing. This makes for relatively complex systems, costly to manufacture, and with many points of potential failure. They are therefore limited in their functionality, difficult to upgrade, and/or relatively expensive.

[0004] International Patent Application Publications No. WO 2012/155245 and No. WO

2013/170378, which are hereby incorporated by reference herein in their entireties, disclose systems and methods for operating external sensors connected to the audio port of an electronic device such as a smartphone or the like. For certain sensor and device combination thereof the native audio hardware system of an electronic device may not provide sufficient power, signal conditioning and control, sampling rate, bit resolution and/or channels.

[0005] The inventors have determined a need for improved systems and methods for operating external sensors using portable electronic devices such as smartphones and the like.

SUMMARY [0006] One aspect of the present disclosure provides apparatus for connecting one or more external sensors to a computing device. The apparatus comprises a digital input/output port configured to connect to a corresponding digital input/output port of the computing device, an analog audio interface comprising a plurality of contacts connectable to the one or more external sensors, an audio processing unit comprising a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC), a digital communication protocol interface, the audio processing unit operably connected to the digital input/output port, and, signal conditioning circuitry connected between the audio processing unit and the analog audio interface.

[0007] Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.

[0009] Figure 1 is a diagram of an example portable diagnostic pulse oximetry system according to one embodiment. [0010] Figure 2 schematically illustrates an example system for controlling an electronic device to operate an external sensor connectable to an audio interface of an audio bridge coupled to a digital port of the electronic device according to one embodiment.

[0011] Figure 2A schematically illustrates an example system for controlling an electronic device to operate an external sensor connectable to an audio interface of an audio bridge coupled to a digital port of the electronic device according to another embodiment.

[0012] Figure 2B schematically illustrates an example audio bridge according to another embodiment.

[0013] Figure 3 schematically illustrates an example audio bridge having an audio interface for connecting to an external sensor and a digital port for connecting to a computing device according to one embodiment.

[0014] Figure 3A schematically illustrates an example audio bridge that includes a sensor according to one embodiment.

[0015] Figure 4 schematically illustrates an example audio bridge having an additional audio interface.

[0016] Figure 4A schematically illustrates example audio bridges having an additional digital port to allow multiple audio bridges to be connected together in daisy-chain fashion according to another embodiment.

[0017] Figure 4B schematically illustrates an example audio bridge having an additional audio interface and associated circuitry according to another embodiment.

[0018] Figure 5 schematically illustrates example audio bridges having an additional reference input for receiving a reference signal according to another embodiment.

[0019] Figure 6 is a flowchart illustrating an example method implemented by an audio bridge according to one embodiment.

[0020] Figure 7 is a flowchart illustrating an example method implemented by a computing device connected to an audio bridge according to one embodiment.

DETAILED DESCRIPTION

[0021] Generally, the present disclosure provides apparatus, methods and systems for overcoming the limitations of typical low-cost mobile devices, and enabling them to effectively operate external sensors. The solutions disclosed herein have several different aspects including both hardware and software embodiments. [0022] PROBLEM STATEMENT

[0023] International Patent Application Publications No. WO 2012/155245 and No.

WO 2013/170378 referred to above describe methods and systems for monitoring human physiological measures with various external sensors, including a pulse oximeter. Typical mobile devices such as smartphones and tablets are coupled with sensors through the audio port. The sensors are directly driven by the AC audio signal and the response from the sensors is received at the microphone channel. Software on the mobile devices processes the signals and analyzes the data to extract physiological measures. The methods and systems described in these published applications presume that there is adequate voltage, power, sampling rate, number of channels and other controls available at the audio system of the mobile device to operate the sensors in a dynamic range sufficient to the circumstances. In the example of pulse oximetry, given the use of typical LEDs, the voltage must be high enough to drive them beyond their forward bias threshold. As well, there must be sufficient power within the audio signal to illuminate the LEDs to the luminosity levels required.

Depending on the specification of the sensor components, the native audio system of a given mobile device may be inadequate - in either voltage or power - to drive a particular sensor. And, given the variability of commercially available mobile devices, not all of them may be able to support the methods and systems described in these published applications. Many low-cost smartphones and tablets employ under-powered components to reduce their build cost. Further, given the high degree of variability in models, even where sufficient power is available, it may be commercially infeasible to adapt the system to work across a large number of different devices with different audio characteristics.

[0024] Further, certain capabilities may not be available in some mobile devices that are needed to implement the physiological monitoring effectively and in a commercial environment. Some implementations of the systems described in International Patent

Application Publications No. WO 2012/155245 and No. WO 2013/170378 require software control of the microphone gain and the speaker volume (in some cases, independent controls for the Left and Right speaker). Not all operating systems and/or mobile audio systems provide this degree of control. Some devices may not have input channels in their audio system. Similarly, it may be desirable to implement hardware filters unique to vital signs monitoring and control them selectively via software. [0025] In some applications it may be desirable to implement external sensors with the means for unique identification, such as for example through a Universal Identifier (UID) or serial number to protect it from counterfeit or inappropriate use. Another authentication technique could involve on-the-fly scrambling/descrambling of input and output signals using a real-time firmware based cipher, to prevent unauthorized software from communicating with the sensors.

[0026] In some applications it may be desirable to connect and operate two or more audio-controlled sensors simultaneously on the same mobile device without increasing the complexity of the signal processing. Similarly, it may be desirable to support simultaneous access of an app to an audio system for the usual purpose of producing and recording sounds as well as operating one or more sensors - this is an important feature for uses of pulse oximetry to monitor application of anesthetics in operating theatres where audio feedback is used as a critical indicator of patient condition.

[0027] In some applications, certain parameters such as calibration values need to be associated with a specific sensor. These parameters need to be digitally stored and associated with the sensor.

[0028] INTRODUCTION TO PROPOSED SOLUTIONS

[0029] The present disclosure provides an additional digital interface between the driving software running on a computing device and the analog audio signal applied to the audio interface. This technique may be used to extend the audio capabilities of

smartphones, tablets, or other computing devices, and facilitates the implementation of the methods and systems described in International Patent Application Publications No. WO 2012/155245 and No. WO 2013/170378. Practically, it becomes possible to mitigate the variability in smartphone and tablet design and manufacture by managing the characteristics of the audio system available to software implementing such methods and systems (which may be referred to as an "application" or simply "app"). An external audio system approach ensures that the power, dynamic response and other characteristics of the audio system is known and adequate for the sensor in use, and allows for additional features and capabilities to be exposed for use by the application. It also ensures unified input/output characteristics of such audio systems between computing systems.

[0030] In a typical prior art implementation, when an external audio system is connected to a computing device, the computing device recognizes the external audio system as such and uses it to replace the native audio system, such that applications requiring audio will use the external audio system instead of the native audio system. In contrast, as discussed further below, the present disclosure provides for connection of an external audio system that does not replace a native audio system of a mobile device, but rather provides an additional audio system accessible by applications running on the mobile device for controlling physiological sensors. The native audio system of the device is thus still available for other applications of functions.

[0031] The examples herein are discussed in the context of an external audio system that provides analog audio-type signals to, and receives analog audio-type signals from, external sensors. The techniques disclosed herein may also be applied to other types of digital interfaces for operating other types of external sensors, for example, sensors that operate based on DC signals, pulse-width-modulated signals, or other types of signals.

[0032] Connecting through an External Digital Interface:

[0033] In the cases where mobile devices do not offer sufficient voltage or power at their audio system outputs to drive certain sensors, it is possible to augment a mobile device with an external audio system through a standardized digital interface such as the commonly available USB port. Solutions exist for peripherals to be added to mobile devices through, for example, a USB port or other suitable digital interface.

[0034] USB-connected sound cards are relatively common and based on commodity audio chips. They are most often used for devices missing an audio system, a defective audio system, or when it is desirable to significantly increase the quality over the native system. However, mobile devices are not the usual targets for prior art USB sound cards. Typically prior art USB sound cards use the Standard A type full-sized USB connector intended for use on laptops and desktop computers. Mobile devices with USB ports typically use a micro USB port such as a micro-A or micro-B port, or a micro-A/B port for devices with USB On-The-Go (OTG) capability.

[0035] Connecting a prior art USB sound card to a mobile device typically requires that an adaptor be used on the connector. For it to work properly, the mobile device must support the USB OTG feature that allows it to act as a USB host (instead of client). In host mode, the mobile device powers the USB-connected peripheral and allows apps running on the mobile device to connect to it. As USB is a standard, there are specifications for the amount of power that must be available at the USB interface while in host mode. [0036] Instead of implementing a real-time audio control layer to access the native audio system through the operating system of the mobile device, an application can implement an interface through the USB interface of the operating system to access and control an externally connected audio system. The present disclosure provides custom- designed externally connected audio systems configured for operation of physiological sensors. The USB interface is a well-defined digital standard that is typically supported by most modern mobile operating systems and is widely available.

[0037] Bonding and Identification:

[0038] As the systems described International Patent Application Publications No. WO 2012/155245 and No. WO 2013/170378 involve analog AC-coupled sensors, it is particularly challenging to implement a hardware-based identification capability into such a sensor that does not interfere with its operation as a vital signs monitoring probe or make the sensor hardware design exceedingly complex, unreliable, or costly to make.

[0039] Through a digital interface such as a USB interface, additional features may be cost-effectively included on a custom-designed external digital audio interface.

Communication between the app and the sensor through a digital interface avoids the complexities of purely analog communications. A low-cost commodity universally unique identifier (UUID) mechanism or an identifier code implemented directly on the audio processing chip, may be included with no direct impact on the performance of the audio system and the AC-coupled sensor.

[0040] Multiple Use of Audio Systems:

[0041] In the systems described in International Patent Application Publications No.

WO 2012/155245 and No. WO 2013/170378, the sensors are typically plugged into the audio port of the mobile device. While in operation, the audio system is dedicated to driving the sensors and cannot be used to answer phone calls, listen to music, or other functions.

[0042] By utilizing an external audio system via USB, an app may drive the sensors while that app or another app uses the native audio system for other purposes. The external system would be dedicated to the vital signs monitoring operation and not replace the audio system used by the operating system of the mobile device.

[0043] Multiple Sensors:

[0044] In the systems described in International Patent Application Publications No.

WO 2012/155245 and No. WO 2013/170378, one set of sensors is driven to fulfill a single vital signs monitoring goal. For example, a pair of LEDs are driven for pulse oximetry, or a strain sensor is driven for use in blood pressure monitoring. In order to change the function of the mobile device as a medical device, sensors would ostensibly need to be unplugged and different sensors plugged in.

[0045] A typical native audio system only provides a single microphone channel and a single pair of stereo speaker channels. It is possible to multiplex driving signals for more than one sensor through the speaker channels and subsequently de-multiplex them on the microphone channel. Each sensor type can be conceived of having distinct driving signals that do not interfere with each other - for example a temperature probe and a pair of LEDs for pulse oximetry might be driven by two distinct signals that can be sent at the same time. Using a custom-designed external audio system connected to a USB or other digital interface however, it is possible to provide for operation of multiple sensors using a variety of techniques, such as for example: including a standard audio processing chip that has multiple audio and microphone channels (e.g., existing 5.1 and 7.1 USB-based audio interfaces offer multiple audio channels and stereo microphone channels, and these could be adapted for controlling physiological sensors); multiple audio processing chips/systems on a single external audio system such that each drive a single sensor on each of several distinct audio ports; a custom audio chip that implements a multiplicity of speaker and microphone channels; or providing an external audio system with an additional digital port that allows multiple instances of an apparatus for driving a single sensor each to be daisy-chained together.

[0046] Chip Implementation:

[0047] The initial stage of the sensor operation systems disclosed herein is composed of a means of generating waveforms that drive sensors and receiving the response signals back. The subsequent stages demultiplex and analyze the response signals. The initial stage may be implemented into hardware, either in a chip alongside a commodity audio system chip or within a custom audio processing chip. The commodity or custom audio chip may be implemented on an external digital audio interface as an external audio system, which may be referred to as an "audio bridge." Alternatively, a custom audio chip may be implemented as a replacement for a standard audio system within a mobile device. [0048] In some embodiments, the entire external audio system can be implemented on a custom audio chip. The chip will have a built-in USB interface, audio power output drivers and as many input and output channels as required. In some embodiments, the chip can also include a synthesizer to drive the sensors independent of the device to reduce the load on the mobile system or provide direct signal modulation/demodulation capability. This custom chip can be a dedicated DSP, an ASIC chip or an audio processor with built-in MCU.

[0049] The audio processing chip can be implemented using a general purpose processor/controller with appropriate digital interface capability with the host device and peripheral audio codecs with sufficient number of channels and other capabilities.

[0050] EXAMPLE EMBODIMENTS

[0051] Referring to Figure 1 , a portable diagnostic pulse oximetry system 100 is shown generally comprising a portable consumer electronic device 110, an oximeter sensor 140, a media connector 120, and an electrical cable 130. The portable consumer electronic device 1 10 generally comprises a processor, a memory, various input/output means (such as, for example, a touch screen display, a display and a physical keyboard, etc.), and at least one digital input/output (I/O) port 205 (not shown in Figure 1 , see Figure 2) such as a

Universal Serial Bus (USB) port, Apple's Lightning or 30 pin connector or the like. In the illustrated embodiment, the portable consumer electronic device 1 10 is a mobile phone. Alternatively, device 1 10 may be any electronic device with an audio interface or digital I/O port, and suitable processing capabilities.

[0052] An audio bridge 1000 according to an example embodiment is connected to the digital I/O port of the electronic device. As described further below and shown in Figures 2-3, the audio bridge 1000 includes an analog audio port 11 15 (such as, e.g. a TRRS audio port, or a custom audio connection port) configured to receive the media connector 120 (e.g. a TRRS audio plug) of the oximeter sensor 140. Although the Figure 1 example depicts an oximeter sensor 140, it is to be understood that the audio bridge 1000 could be connected to other types of sensors.

[0053] Further, in some embodiments, instead of being removeably connected to the audio bridge 1000 by a media connector, in some embodiments one or more sensors may be permanently connected to the audio bridge. Such a configuration would permit the authenticity of the sensor(s) to be verified by including a UUID in the audio bridge 1000. [0054] Figure 2 shows an example system 200 according to one embodiment.

System 200 may be implemented in an electronic device 1 10 to control an audio bridge 1000 with an audio interface 1115 to operate an external sensor and process the response signals from the sensor. In the illustrated embodiment, audio interface 1 115 comprises a TRRS (tip, ring, ring, sleeve) audio interface wherein the tip and first ring comprise speaker contacts SPK, the second ring comprises a ground contact GND, and the sleeve comprises a microphone contact MIC, but it is to be understood that different types of audio interfaces may be used. For example, some embodiments may use a TRRS audio interface with a different arrangement of contacts. Some embodiments may use a pair of TRS type interfaces (e.g., a speaker output interface and a microphone input interface). Some embodiments may use differently configured audio interfaces with a plurality of contacts for sending and receiving electrical signals. In the illustrated embodiment, system 200 comprises a software based audio driving signal generator 202 for providing driving signals to a digital port 205, which are passed using the standard USB audio protocol to a corresponding port 1005 on the audio bridge 1000, provided to an audio chip 1010 which processes and converts the digital audio driving signals to analog signals.

[0055] In the illustrated example, the audio chip 1010 comprises a digital (e.g. USB) interface 1012, an analog-to-digital- and digital-to-analog-converter (ADC-DAC) 1014, power amplifiers 1016 for amplifying the analog output signals (OUT1 and OUT2 in the illustrated example), an input preamp 1018 for amplifying incoming signals, and a voltage source 1019 for providing a microphone bias voltage. An internal ground (not specifically enumerated) of the audio bridge 1000 is connected to ground contact GND.

[0056] The audio chip 1010 processes digital packets received from the mobile device 1 10, which could either be control commands for speaker volume, signal gain or audio equalizer settings and filtering, or be audio stream data. The sampling frequency of the audio stream is either explicitly set by USB commands or is implied by the packets' arrival timing. The chip audio 1010 may filter the signals before applying them to its power amplifiers 1016. The power amplifiers 1016 will have sufficient drive power/voltage for the desired sensor. The analog driving signals are further processed by signal conditioning circuitry 1020, as described further below, before being applied to speaker contacts SPK or the audio interface 11 15. [0057] An analog response signal is received at a microphone contact MIC of the audio interface 1115, processed by the signal conditioning circuitry 1020 and provided to the audio chip 1010. The audio chip 1010 processes and converts the analog response signal to a digital signal, which is provided to a software based response signal detector 204 through digital ports 1005 and 205. Prior to the conversion to digital, to prevent aliasing the analog signal is filtered by the signal processing circuitry 1020 and amplified by the input preamp 1018. The audio chip 1010 may additionally provide automatic gain control to keep the input signal within a specific range. The audio chip 1010 may also use the received signal's amplitude to adaptively control the intensity of the driving signals applied to the speaker contact SPK. This could be used, for example, in pulse oximetry to keep amplitudes of the red and IR signals within a predetermined range of each other. The sampled data may also go through another stage of digital filtering at the audio chip 1010 for signal conditioning before being transmitted by the USB interface 1012. The audio chip 1010 may optionally also provide a control signal 1011 to the signal conditioning circuitry 1020, for example to turn various hardware filters on or off to tailor the signal conditioning to a particular type of sensor.

[0058] The response signal detector 204 provides feedback to driving signal generator 202 for adjusting the driving signals to appropriate levels if necessary. Driving signal generator 202 provides a physiological parameter extractor 208 with characteristics of the driving signals (e.g. phase and amplitude) for extraction of physiological information. In some embodiments physiological parameter extractor 208 receives a balance signal indicating a ratio of amplitudes of the driving signals. In some embodiments physiological parameter extractor 208 may also receive one or more signals generated based on the response signal received by response signal detector 204, as indicated by the dotted line connecting response signal detector 204 and physiological parameter extractor 208.

Physiological parameter extractor 208 determines one or more physiological parameters based on characteristics of the driving signals, and optionally based on the response signal, as described further below, and provides the determined physiological parameter(s) for output at output 210.

[0059] Alternatively, the software based response signal detector 204 and/or the driving signal generator can be implemented on the audio chip to reduce the processing burden on the host device and/or the USB bandwidth. [0060] Figure 2A shows an example system 200A according to one embodiment.

System 200B may be implemented in an electronic device such as device 110 to control an audio bridge 1000 with an audio interface 11 15 to operate an external sensor. System 200A is similar to system 200 discussed above, but is specifically adapted for pulse oximetry. In the illustrated embodiment, system 200A comprises a driving signal generator 202A for providing harmonic digital driving signals to the audio bridge 1000, and a response signal demodulator and demultiplexer 204A for receiving a digital response signal from the audio bridge 1000 and obtaining first and second wavelength components and λ₂ therefrom, and provide first and second wavelength components and λ₂ to a response signal analyzer 208A, which determines one or more vital signs and provides the determined vital signs to output 210. In some embodiments response signal demodulator and demultiplexer 204A may also optionally determine an error signal ERR from the response signal, as indicated by the dotted line connecting response signal demodulator and demultiplexer 204A to response signal analyzer 208A. For example, response signal demodulator and demultiplexer 204A may be configured to generate error signal ERR to indicate when the received response signal has unexpected characteristics (e.g., an amplitude, DC offset or frequency outside of an expected range), such that response signal analyzer 208B may disregard potentially spurious readings in first and second wavelength components h and λ₂ . In some embodiments first and second wavelength components h and λ₂ may also optionally be provided to driving signal generator 202A, as indicated by the dotted lines connecting first and second wavelength components h and λ₂ to driving signal generator 202A, for use as feedback in controlling parameters of the harmonic driving signals.

[0061] Systems 200 and 200A may also implement particular signal generation and processing techniques which are described in detail in International Patent Application Publications No. WO 2012/155245 and No. WO 2013/170378.

[0062] Figure 2B shows an example audio bridge 1000A according to another embodiment. Audio bridge 1000A is similar to audio bridge 1000 discussed above except that in audio bridge 1000A the audio chip 1010 is replaced with a customized general purpose controller 1013, a first codec with DAC 1014A, and a second codec with ADC 1014B. The controller 1013 communicates with the electronic device 1 10 through the digital port 1005. Outgoing signals are converted to analog, and amplified if necessary, by the codec with DAC 1014A, and incoming signals are converted to digital, and amplified if necessary, by the codec with ADC 1014B. The codec with ADC 1014B may also provide a microphone bias voltage. The codecs 1014A, 1014B may be connected to the controller 1013 through an appropriate digital interface (e.g. I2S bus). The controller 1013 may optionally also provide a control signal 101 1 to the signal conditioning circuitry 1020.

[0063] Figure 3 is a block diagram schematically illustrating elements of an example audio bridge 1000B according to one embodiment. The audio bridge combines the microphone input and speaker outputs into a single audio interface 11 15 (e.g. a TRRS jack) compatible with most mobile devices. The microphone bias voltage (BIAS) and microphone input signal (IN) are therefore combined into a single line and connected to the

corresponding contact (MIC) on the audio interface 11 15.

[0064] In the Figure 3 example, the signal conditioning circuitry 1020 comprises a low pass filter 1022 on the microphone bias line (BIAS) from the chip 1010 that provides supply voltage for the sensor, such that the MIC contact has a specific source impedance required by the sensor. In certain pulse oximetry implementations, the impedance may be about 2.2 k to ensure proper biasing of the audio oximeter. The signal conditioning circuitry 1020 comprises a high pass filter 1024 on the microphone input line to remove the DC component (including the bias voltage) and condition the incoming signal based on its frequency. In the case of audio pulse oximetry, for example, with the signal modulated at frequencies close to 1 k, the cutoff frequency of the filter can be selected to be 800 Hz. This reduces low frequency noise and can also significantly reduce interferences from ambient lighting (60 Hz & 120 Hz and their harmonics) or mains power. The high pass filter 1024 can be

implemented with passive or active components. Optionally, the filters can be controlled through software and a general purpose output 101 1 (see Figure 2) from the chip 1010 which controls the gain/filter settings. Alternatively, for some applications the microphone input line can be DC coupled to the signal. This will facilitate connection of sensors whose output is inherently at very low frequency or DC.

[0065] The signal conditioning circuitry 1020 optionally comprises high pass filters or band pass filters 1026 on the outputs (OUT1 , OUT2) from the chip 1010. If the audio chip 1010 lacks power amplifiers to provide sufficient drive power/voltage for the intended sensor, the output filters 1026 can be combined with amplifiers 1028 for driving sensor at the required power/voltage level. Alternatively, for some applications the outputs (OUT1 , OUT2) from the chip 1010 may be connected to the speaker contacts (SPK) of the audio interface 11 15 directly. Direct connection allows adjusting the DC level of the output signals, which is required in some applications, such as for example independent control of red and IR LED amplitudes for pulse oximetry. AC coupling of the outputs (OUT1 , OUT2) from the chip 1010 to the speaker contacts (SPK) of the audio interface 1 115 can be accomplished by a single capacitor or by more complex filtering methods.

[0066] Figure 3A is a block diagram schematically illustrating elements of an example audio bridge 1000C according to another embodiment. The audio bridge 1000C is similar to audio bridge 1000B of Figure 3 except that audio bridge 1000C includes an integrated sensor 1500 instead of an audio interface 1 115 for connecting to an external sensor.

[0067] Figure 4 schematically illustrates an example audio bridge 1000D according to another embodiment. The audio bridge 1000D comprises an additional audio interface 11 15A for enabling an additional sensor to be operated through the audio bridge. Although only one additional audio interface 1 115A is shown in Figure 4, the audio bridge 1000D could have as many additional audio interfaces 1 115A as may be supported by the audio chip 1010. For example, an audio bridge 1 115 having a chip 1010 with five audio input/output channels could have five additional audio interfaces 11 15A.

[0068] Figure 4A schematically illustrates example audio bridges 1000E according to another embodiment. Audio bridges 1000E each comprise an additional digital port 1015, and digital (e.g. USB) interface 1007 that enables the bridge 1000E to act as a USB hub or the like. The digital interface 1007 allows connection of multiple audio bridges 1000E to a single port on the mobile device 1 10 without degrading the data signal or overloading the power line on the digital (e.g. USB) connection. The digital interface 1007 could be, for example a simple USB data repeater or a USB hub with more complex functionalities. For example, the digital interface 1007 may be configured to report multiple USB ports back to the OS of the device 1 10 so that the software can treat each sensor as being connected to an independent digital (e.g. USB) port. As shown in Figure 4A, the main digital port 1005 of a first audio bridge 1000E is coupled to a corresponding port (not shown) of an electronic device 1 10, and the main digital port 1005 of a second audio bridge 1000E is coupled to the additional digital port 1015 of the first audio bridge 1000E. Additional audio bridges 1000E may be added in similar fashion. This configuration permits multiple audio bridges 1000E to be "daisy-chained" together to allow the operation of multiple external sensors from a signal electronic device 110. This configuration also allows devices of other USB classes (e.g. USB storage, HID, etc.) to be accessible by the host device. External sensors can include normal audio signal for user feedback or other purposes as well as other audio controlled

transducers.

[0069] Figure 4B schematically illustrates an example audio bridge 1000F according to another embodiment. The audio bridge 1000F is similar to audio bridge 1000D of Figure 4 except that audio bridge 1000F includes additional signal conditioning circuitry 1020A for the additional audio interface 1 115A, and the audio chip 1010 is replaced with a customized general purpose controller 1006 and two codecs with ADC-DAC 1017, 1017A. The controller 1006 communicates with the electronic device 110 through the digital port 1005, and drives the codecs with ADC-DAC 1017, 1017A through an appropriate digital interface (e.g. I2S bus). This allows connection of multiple sensors to the audio bridge without requiring more complicated audio interface chips.

[0070] Figure 5 schematically illustrates an example audio bridge 1000G according to another embodiment. A generic sensor 150 is shown as being removeably coupled to the audio interface 1 115 of the audio bridge 1000G through a TRRS plug 120 in the illustrated example, but it is to be understood that the sensor 150 could alternatively be permanently connected to the audio bridge 1000G. Audio bridge 1000G comprises an auxiliary input 1100 (which may, for example, comprise another microphone input or the like) for receiving an additional input from a reference signal source 1 120 indicative of ambient conditions in the region of the sensor 150. The additional input is provided to the audio chip 1010 for, for example adaptive echo/noise cancellation or other custom adaptive algorithms. The reference signal can be passed to the mobile device 1 10 for processing. Alternatively, the audio chip 1010 may have echo cancellation built-in that may be used for this purpose. The reference signal source 1 120 could, for example, provide an indication of ambient lighting, noise, or motion artifacts. The signal from the reference signal source 1120 may optionally be passed through a filter 1125 to improve the quality thereof.

[0071] Figure 6 is a flowchart illustrating an example method 2000 which may be carried out by an audio bridge in some embodiments. A digital driving signal from a computing device is received at 2002 and converted to analog at 2004 before being applied at 2006 to the speaker outputs of an audio jack. The driving signal may optionally also be filtered and/or amplified before being applied to the speaker contacts of an audio jack, as discussed above. The method also comprises applying a microphone bias voltage at 2008 to the microphone contact. An analog response signal from an external sensor is received at 2010. The analog response signal is filtered (e.g. high pass filtered) at 2012, converted to digital at 2014 and outputted to the computing device at 2016.

[0072] Figure 7 is a flowchart illustrating an example method 3000 implemented by a computing device connected to an external audio system such as, for example, an audio bridge, according to one embodiment. The example method 3000 includes details for a particular software implementation for use with a USB-based audio bridge that may not be present in all embodiments. In one implementation, the software driver uses the open source libusb library and all communications with the usb audio bridge uses standard USB communications specified under the USB specifications. For android implementation, the libusb library is a modified USB library with custom functions that allows mobile applications to directly use USB devices with isochronous endpoints. The standard libusb library itself cannot be used to build the driver for operating the audio bridge as a result of security reasons for Android or linux-based devices.

[0073] The audio bridge is connected via the micro-USB OTG port of the mobile device. Upon connection, the host device may or may not have the native generic drivers for USB audio cards. When the host device has such drivers, the host device may claim the audio bridge completely (3008, 3014 "Yes" outputs) and audio is routed only through the audiobridge rendering the internal audio system of the device inactive. The software driver for the audio bridge automatically detaches (3010, 3016) the audio bridge hardware from the host device's OS kernel and claims the audio bridge (3012, 3018) as a separate USB device. This allows the host device's to route any audio signals to the native sound interface and sensor-based audio signals to the usb audio bridge. When the host device does not have the generic drivers for usb audio sound cards (3008, "No" output), the software driver simply claims the audio bridge device (3012) and enables it (3020) for sensor operations. Once this is completed, the audio driver enters a threaded main loop (3022-3028) that continuously outputs audio signal driven by the physiological monitoring signal processor and feeds the input from the microphone into the signal processor. The audio bridge interfaces itself between the USB audio bridge hardware and the physiological monitoring digital signal processing application(s) that operate the sensor(s), hence there are no interactions with the end user directly. [0074] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details are not required. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the understanding. For example, specific details are not provided as to whether the embodiments described herein are implemented as a software routine, hardware circuit, firmware, or a combination thereof.

[0075] Embodiments of the disclosure can be represented as a computer program product stored in a machine-readable medium (also referred to as a computer-readable medium, a processor-readable medium, or a computer usable medium having a computer- readable program code embodied therein). The machine-readable medium can be any suitable tangible, non-transitory medium, including magnetic, optical, or electrical storage medium including a diskette, compact disk read only memory (CD-ROM), memory device (volatile or non-volatile), or similar storage mechanism. The machine-readable medium can contain various sets of instructions, code sequences, configuration information, or other data, which, when executed, cause a processor to perform steps in a method according to an embodiment of the disclosure. Those of ordinary skill in the art will appreciate that other instructions and operations necessary to implement the described implementations can also be stored on the machine-readable medium. The instructions stored on the machine- readable medium can be executed by a processor or other suitable processing device, and can interface with circuitry to perform the described tasks.

[0076] The above-described embodiments are intended to be examples only.

Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for connecting one or more external sensors to a computing device, the apparatus comprising: a digital input/output port configured to connect to a corresponding digital input/output port of the computing device; an analog audio interface comprising a plurality of contacts connectable to the one or more external sensors; an audio processing unit comprising at least a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC), a digital communication protocol interface, the audio processing unit operably connected to the digital input/output port; and, signal conditioning circuitry connected between the audio processing unit and the analog audio interface.

2. The apparatus of claim 1 wherein the plurality of contacts comprises a microphone contact, and wherein the signal conditioning circuitry comprises a low pass filter on a bias line between the audio processing unit and the microphone contact.

3. The apparatus of claim 2 wherein the signal conditioning circuitry comprises a high pass filter on an input line between the audio processing unit and the microphone contact.

4. The apparatus of claim 1 wherein the plurality of contacts comprises two speaker contacts, and wherein the signal conditioning circuitry comprises high pass or band pass filters on output lines between the audio processing unit and the speaker contacts.

5. The apparatus of claim 4 wherein the signal conditioning circuitry comprises output amplifiers on output lines between the audio processing unit and the speaker contacts.

6. The apparatus of claim 1 wherein the audio processing unit comprises one or more audio power amplifiers connected to one or more output lines.

7. The apparatus of claim 1 wherein the audio processing unit comprises an input preamp connected to an input line.

8. The apparatus of claim 1 comprising an additional digital input/output port and digital interface for enabling the apparatus to act as a hub such that another apparatus according to claim 1 may be connected to the additional digital input/output port.

9. The apparatus of claim 1 comprising one or more additional analog audio interfaces.

10. The apparatus of claim 1 comprising an auxiliary input for receiving a reference signal indicative of ambient conditions.

11. The apparatus of claim 1 comprising an external sensor permanently connected to the analog audio interface, and a universal unique identifier.

12. A method for operating one or more external sensors with a computing device having a native audio system, the method comprising: detecting a connection of an external audio system to a digital interface of the computing device; in response to detecting the connection, claiming the digital interface for one or more sensor applications while preventing claiming of the digital interface for applications for other functions such that the applications for other functions continue to use the native audio system; and operating an external sensor connected to the external audio system by sending one or more sensor driving signals from the one or more sensor applications to the digital interface and receiving one or more sensor response signals from the digital interface at the one or more sensor applications.

13. The method of claim 12 wherein the external audio system comprises an apparatus according to any one of claims 1 to 11.