Abstract:
A field testing system is provided that uses a personal computer tethered to an interface board. A cellular telephone plugs into the interface board during wireless field testing. The cellular telephone may include configurable multiplexer circuitry and power supply circuitry. During normal operation, the cellular telephone is configured so that its application processor is linked to its application processor and to an external bus. During field testing, the cellular telephone is configured to link the baseband unit to the external bus and the interface board. The baseband unit may support advanced communications busses (e.g., USB). To avoid consuming too many pins in the external bus between the interface board and the cellular telephone, power for the USB bus during field testing may be derived from a power management unit in the cellular telephone.

Description:
BACKGROUND 
     This relates to radio-frequency testing circuitry and, more particularly, to cellular telephones with configurable multiplexer circuitry and local bus power for field testing. 
     Handheld electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. 
     Due in part to their mobile nature, handheld electronic devices are often provided with wireless communications capabilities. Handheld electronic devices may use wireless communications to communicate with wireless base stations. 
     As part of developing wireless devices for consumers, manufacturers routinely field test the real-world radio-frequency performance of these devices. Manufacturers also strive to reduce the size and number of components used in these devices. With conventional field testing systems, the devices need dedicated circuitry and external connectors to connect to external testing equipment during field testing. These extra components may take up an undesirably large amount of space in the devices. 
     It would therefore be desirable to be able to provide improved configurable multiplexer circuitry and local bus power for field testing for electronic devices. 
     SUMMARY 
     A cellular telephone may be provided with configurable multiplexer circuitry and local bus power. The cellular telephone may be tested using a field testing system. The system may also include a personal computer tethered to an interface board. The cellular telephone may plug into the interface board during wireless field testing to monitor the operation of a baseband processor in the cellular telephone. 
     The cellular telephone may include configurable multiplexer circuitry. The configurable multiplexer circuitry may allow external access to a bus that is shared between an applications processor and a baseband processor in the cellular telephone. If desired, the external bus may be a universal serial bus (USB). The configurable multiplexer may couple the baseband processor to the external bus during wireless field testing and may couple the applications processor to the external bus during normal operation. When the configurable multiplexer circuitry couples the cellular telephone&#39;s baseband processor to the external bus during wireless testing, the personal computer and the interface board may communicate with the baseband processor over the external bus as part of testing the wireless performance of the cellular telephone (e.g., by analyzing the signals from the baseband processor). 
     With one suitable arrangement, the cellular telephone may include a power management unit. The power management unit may generate one or more power supply voltages used in the external bus. With this type of arrangement, the number of pins in an external connector of the cellular telephone is reduced because power supply voltages that would otherwise require a pin are provided locally. Reducing the number of pins in the external connector that are used in providing the external bus may be desirable in cellular telephones and other devices in which the number of pins in the external connector is constrained (e.g., when the external connector is pin constrained). If desired, the power management unit may generate control signals that control whether the configurable multiplexer circuitry couples the baseband processor or the applications processor to the external bus. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative handheld electronic device that may have configurable multiplexer circuitry and local bus power for field testing in accordance with accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic diagram of an illustrative handheld electronic device that may have configurable multiplexer circuitry and local bus power for field testing in accordance with an embodiment of the present invention. 
         FIG. 3  is a schematic diagram of illustrative circuitry that may include configurable multiplexer circuitry and local bus power for field testing in a handheld electronic device and a testing device in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of illustrative testing circuitry in a handheld electronic device and a testing device that may connect to the handheld electronic device during field testing in accordance with an embodiment of the present invention. 
         FIG. 5  is a schematic diagram of an illustrative testing interface device, a testing device, and a device under test that shows how the testing device may be coupled to the device under test through the testing interface device during field testing in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of a conventional cellular telephone with multiplexer circuitry to support testing. 
     
    
    
     DETAILED DESCRIPTION 
     This relates to radio-frequency field testing circuitry and, more particularly, to electronic devices such as cellular telephones with configurable multiplexer circuitry and local bus power for field testing. 
     The configurable multiplexer circuitry may allow external pins in a connector in an electronic device to be used for different purposes during normal operation and testing operations. For example, the external pins may be coupled through the configurable multiplexer circuitry to an application processor in the device during normal operation. During testing (e.g., during field testing), the external pins may be coupled through the configurable multiplexer circuitry to baseband circuitry in the device. Using the configurable multiplexer circuitry, the number of pins needed to support normal operation and testing operations may be minimized. 
     An electronic device may include a power management unit that provides local bus power to serve as a power signal for a communications bus (e.g., a communications bus that includes a power signal on a power line). By providing the power signal locally, the number of external pins needed to support the communications path is minimized. 
     The electronic devices may be portable electronic devices such as laptop computers or small portable computers of the type that are sometimes referred to as ultraportables. Portable electronic devices may also be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, which is sometimes described herein as an example, the portable electronic devices are handheld electronic devices. Handheld devices may be, for example, cellular telephones, media players with wireless communications capabilities, handheld computers (also sometimes called personal digital assistants), remote controllers, global positioning system (GPS) devices, and handheld gaming devices. The handheld devices may also be hybrid devices that combine the functionality of multiple conventional devices. Examples of hybrid handheld devices include a cellular telephone that includes media player functionality, a gaming device that includes a wireless communications capability, a cellular telephone that includes game and email functions, and a handheld device that receives email, supports mobile telephone calls, and supports web browsing. These are merely illustrative examples. 
     An illustrative handheld electronic device such as a cellular telephone in accordance with an embodiment of the present invention is shown in  FIG. 1 . Device  10  may be any suitable portable or handheld electronic device. 
     Device  10  may have housing  12 . Device  10  may include one or more antennas for handling wireless communications. Embodiments of device  10  that contain one antenna and embodiments of device  10  that contain two or more antennas are sometimes described herein as examples. 
     Device  10  may handle communications over one or more communications bands. For example, in a device  10  with two antennas, a first of the two antennas may be used to handle cellular telephone communications in one or more frequency bands, whereas a second of the two antennas may be used to handle data communications in a separate communications band. With one suitable arrangement, which is sometimes described herein as an example, the second antenna is configured to handle data communications in a communications band centered at 2.4 GHz (e.g., WiFi and/or Bluetooth® frequencies). If desired, device  10  may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile Communications or GSM cellular telephone bands). Device  10  may also use other types of communications links. For example, device  10  may communicate using the WiFi® (IEEE 802.11) band at 2.4 GHz and 5 GHZ and the Bluetooth® band at 2.4 GHz. Communications are also possible in data service bands such as the 3G data communications band at 2170 MHz band (commonly referred to as UMTS or Universal Mobile Telecommunications System). 
     Housing  12 , which is sometimes referred to as a case, may be formed of any suitable materials including, plastic, glass, ceramics, metal, or other suitable materials, or a combination of these materials. Bezel  14  may be used to attach display  16  to housing  12 . 
     Display  16  may be a liquid crystal diode (LCD) display, an organic light emitting diode (OLED) display, a plasma display, multiple displays that use one or more different display technologies, or any other suitable display. The outermost surface of display  16  may be formed from one or more plastic or glass layers. If desired, touch screen functionality may be integrated into display  16  or may be provided using a separate touch pad device. 
     Handheld electronic device  10  may have user input control devices such as button  19  and input-output components such as port  20  and one or more input-output jacks (e.g., for audio and/or video). Button  19  may be, for example, a menu button. Port  20  may contain a 30-pin data connector (as an example). Openings  24  and  22  may, if desired, form microphone and speaker ports. Opening  23  may form a speaker port. 
     A schematic diagram of an embodiment of an illustrative electronic device is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may include storage  34 . Storage  34  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., battery-based static or dynamic random-access-memory), etc. 
     Processing circuitry  36  may be used to control the operation of device  10 . Processing circuitry  36  may be based on a processor such as a microprocessor and other suitable integrated circuits. Processing circuitry  36  may include a baseband processor and an applications processor, as examples. 
     Input-output devices  38  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Display screen  16 , button  19 , microphone port  24 , speaker port  22 , and dock connector port  20  are examples of input-output devices  38 . 
     Input-output devices  38  can include user input-output devices  40  such as buttons, touch screens, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, etc. Display and audio devices  42  may include liquid-crystal display (LCD) screens or other screens, light-emitting diodes (LEDs), and other components that present visual information and status data. Display and audio devices  42  may also include audio equipment such as speakers and other devices for creating sound. Display and audio devices  42  may contain audio-video interface equipment such as jacks and other connectors for external headphones and monitors. 
     Wireless communications devices  44  may include communications circuitry such as radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, passive RF components, transmission lines, one or more antennas, and other circuitry for handling RF wireless signals. 
     During normal operation, device  10  can communicate with external devices such as accessories  46  and computing equipment  48 , as shown by paths  50 . Paths  50  may include wired and wireless paths. For example, paths  50  may include wired paths formed using connector  20  of  FIG. 1 . Accessories  46  may include headphones (e.g., a wireless cellular headset or audio headphones) and audio-video equipment (e.g., wireless speakers, a game controller, other equipment that receives and plays audio and video content), power supplies that provide power to device  10 , etc. If desired, device  10  can communicate with external devices such as accessories  46  and computing equipment  48  during field testing. 
     Computing equipment  48  may be any suitable computer. With one suitable arrangement, computing equipment  48  is a computer that has an associated wireless access point (router) or an internal or external wireless card that establishes a wireless connection with device  10 . The computer may be a server (e.g., an internet server), a local area network computer with or without internet access, a user&#39;s own personal computer, a peer device (e.g., another electronic device  10 ), or any other suitable computing equipment. Device  10  may use wireless communications circuitry  44  to communicate with wireless network  49  over wireless path  51 . 
     During field testing, device  10  serves as a “device under test” and may be connected to testing equipment such as testing device  70  ( FIG. 3 ). 
     As illustrated by  FIG. 3 , device  10  may include processing circuitry and radio-frequency circuitry. For example, device  10  may include a baseband processor such as baseband processor  52  and an applications processor such as applications processor  54 . Additional processors such as digital signal processing circuitry, application-specific integrated circuits, and other processing components may be included in device  10 . Applications processor  54  and baseband processor  52  may be used in supporting radio-frequency communications for device  10 . Applications processor  54  may be coupled to baseband processor  52  over a communications path such as path  53 . 
     Baseband processor  52  may be connected to transceiver circuitry such as transceiver circuitry  56 . Baseband processor  52  may send and receive digital and/or analog signals to and from transceiver circuitry  56  through data paths  58 . Transceiver circuitry  56  may include an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a digital down converters (DDC), and a digital up converter (DUC). As one example, in a scenario in which device  10  is transmitting radio-frequency signals (e.g., when device  10  is transmitting over path  51  to network  49  of  FIG. 2 ), baseband processor  52  may provide digital data (e.g., baseband signals) to the DUC. The DUC may convert or modulate the baseband digital signals to an intermediate frequency (IF). The IF digital signals may be fed to the DAC to convert the IF digital signals to IF analog signals. The IF analog signals may then be fed to a radio-frequency front end such as front end  60 . 
     In a scenario in which device  10  is receiving wireless signals (e.g., when device  10  is receiving radio-frequency signals over path  51  from network  49  of  FIG. 2 ), radio-frequency front end  60  may provide incoming IF analog signals to the ADC. The ADC may convert the incoming IF analog signals to incoming IF digital signals. The incoming IF digital signals may then be feed to the DDC. The DDC may convert the incoming IF digital signals to incoming baseband signals. The incoming baseband digital signals may then be provided to baseband processor  52  for further processing. Transceiver circuitry  56  may sometimes be referred to as an IF stage. 
     Radio-frequency (RF) front end  60  may include circuitry that couples transceiver circuitry  56  to device antennas such as antenna  62 . RF front end  60  may include circuitry such as matching circuits, band-pass filters, mixers, a low noise amplifier (LNA) for incoming signals, a power amplifier (PA) for outgoing signals, etc. In the scenario in which device  10  is transmitting, RF front end  60  may up-convert the IF analog signals from transceiver circuitry  56  to RF analog signals. The RF analog signals may be fed to antenna  62  and broadcast out by device  10 . In the scenario in which device  10  is receiving, antenna  62  may receive incoming RF analog signals from a broadcasting device (e.g., from wireless network  49  over path  51 ). 
     As shown in  FIG. 3 , device  10  may include a connector such as connector  64 . With one suitable arrangement, connector  64  may be a female 30-pin data connector such as port  20  of  FIG. 1 . An external testing device such as testing device  70  may be coupled to device  10 . For example, during laboratory and field testing, testing device  70  may be connected to device  10 . 
     Testing device  70  may include a connector such as connector  66  that mates with connector  64 . With one suitable arrangement, connector  66  may be a male 30-pin data connector that engages with connector  64  in port  20  of device  10 . When device  10  is coupled to device  70 , testing circuitry  68  in device  70  may be coupled to baseband processor  52  and/or applications processor  54 . 
     If desired, device  10  may include configurable multiplexer circuitry such as multiplexer circuitry  72 . During normal operation (e.g., when accessories or devices other than testing device  70  are connected to device  10 ), multiplexer circuitry  72  may route signals such as universal serial bus (USB) signals between applications processor  54  and connector  64 . During testing operations (e.g., when a testing device such a device  70  is connected to device  10 ), multiplexer circuitry  72  may route signals such as USB signals between baseband processor  52  and connector  64 . If desired, multiplexer circuitry  72  may also route signals between processors  52  and  54 . 
     Device  10  may include circuitry such as power management unit (PMU)  74 . PMU  74  may include a general-purpose input-output port (GPIO)  76 . GPIO  76  may control multiplexer circuitry  72 . For example, GPIO  76  may be used to control whether one or more external pins in connector  64  are coupled to applications processor  54  (e.g., during normal operation) or are coupled to baseband processor  52  (e.g., during RF testing operations). PMU  74  may have an input-output port such as IO port  80  that is coupled to applications processor  54 . If desired, applications processor  54  may control the operation of PMU  74  by sending control signals to PMU  74  through the path connected to IO port  80 . 
     If desired, PMU  78  may generate a power supply signal on a power supply path such as voltage bus (VBUS)  78 . The power supply signal that is supplied from PMU  74  may be routed to baseband processor  52 . The power supply signal output from PMU  74  may optionally also be routed to applications processor  54  and/or to multiplexer circuitry  72 . With one suitable arrangement, the power supply signal output from PMU  74  may be used to provide a locally generated version of a communications bus power line signal. This makes it unnecessary to use an external pin in connector  64  to receive communications bus power from device  70 . This type of arrangement may therefore reduce the number of pins needed to provide a communications bus that includes a power line between processors  52  and  54  and an external device such as testing device  70 . 
     A more detailed circuit diagram of the arrangement shown in  FIG. 3  is shown in  FIG. 4 . As shown in the circuit diagram of  FIG. 4 , a testing interface device such as testing interface device  81  may connect to device  10 . 
     Testing interface device  81  may include a connector  82  that connects to connector  64  of device  10 . Testing interface device  81  may include additional connectors such as connectors  84 ,  86 , and  88 . With one suitable arrangement, connectors  84  and  86  may be USB connectors that connect to an external testing device such as a personal computer or a laptop computer that is running testing software. During field testing, connector  88  may be connected to external equipment such as accessories  46  and computing equipment  48  ( FIG. 2 ). 
     Connector  88  may be a 30-pin pass-through connector. As one example, connector  88  may be configured to replicate the functionality of connector  64  for accessories and devices that normally connect to connector  64  (e.g., devices that normally connect to a 30-pin connector in device  10  such as port  20  of  FIG. 1 ). If desired, testing interface device  81  may have a minimal size and may be configured to minimize its impact on the wireless performance of device  10 . With this type of arrangement, the radio-frequency performance of device  10  can be measured and tested with minimal impact from the presence of testing interface device  81 . In addition, the effects of connecting various accessories and devices to device  10  (e.g., through the 30-pin connector) on the RF performance of device  10  can be measured and tested by connecting the accessories and devices to device  10  through connector  88  of testing interface device  81  while using a testing device connected to connectors  84  and/or  86  of testing interface device  81 . 
     Testing interface device  81  may include a multiplexer such as multiplexer  94 . Multiplexer  94  may be controlled by switch  100 . Switch  100  may determine whether signals are routed between connector  82  and connector  84  or connector  86 . As one example, switch  100  may allow node  104  to float and resistor  103  to pull node  104  to ground when it is desired to route signals between connector  84  and connector  82 . Switch  100  may pull node  104  to a power supply voltage such as Vcc2 when it is desired to route signals between connector  86  and connector  82 . As shown in the example of  FIG. 4 , connector  84  may be coupled to connector  82  through a hub such as USB hub  96  and connector  86  may be coupled to connector  82  through a hub such as universal asynchronous receiver-transmitter (UART) hub  98 . 
     Device  10  may include multiplexer circuitry such as multiplexers  73  and  75 . Multiplexers  73  and  75  may be powered by a positive power supply voltage Vcc and may be controlled by signals from GPIO  76  of PMU  74 . As one example, GPIO  76  may allow path  92  to float. As path  92  floats, a resistor such as resistor  90  that is tied to a positive power supply line carrying Vcc can pull path  92  towards Vcc, thereby configuring multiplexers  73  and  73  to route signals for testing operations. During normal operation, GPIO  76  may pull path  92  low, thereby configuring multiplexers  73  and  75  to route signals for normal operation. 
     As part of the testing of baseband processor  52 , multiplexers  73  and  75  may be configured to route USB signals between baseband processor  52  and testing interface device (and then to a testing device through connector  84 ). As an example, signals from ports D+ and D− (e.g., a differential pair of USB data signals) of baseband processor  52  may be routed to a test device so that the test device can communication with baseband processor  54 . 
     Because USB busses typically require power signals (e.g., a 5.0 volt positive power signal and a 0.0 ground signal), PMU  74  may generate USB-spec power signals on power supply line VBUS  78  from an internal power source such as battery  101 . The USB power signals may be routed internally to baseband processor  52  by line  102 , thereby obviating the need for external USB power during testing and reducing the number of pins consumed in connectors  64  and  82 . If the USB power signals had been supplied from connector  82 , an extra conductive line would have been required between connectors  64  and  82 . 
     As part of testing applications processor  54  and during normal operation, multiplexer  75  may route UART signals between applications processor  54  and connector  64 . As an example, UART signals from ports UART 3 _TXD and UART 3 _RXD of applications processor  54  may be routed to a test device (e.g., during testing) or to accessories and other devices (e.g., during normal operation). During testing of applications processor  54  and during normal operation, multiplexer  73  may optionally route USB signals between baseband processor  52  and applications processor  54 . For example, signals may be routed between pins D+ and D− of baseband processor  52  and pins FS_D+ and FS_D− of applications processor  54 . 
     As shown in  FIG. 4 , baseband processor  52  and applications processor  54  may be interconnected by a number of conductive lines and paths. For example, baseband processor  52  may have ports USIF, SIDEBAND, UMTS_TXD and UMTS_RXD (e.g., universal mobile telecommunications transmitting and receiving ports), UART 0 _TXD, UART 0 _RXD, UART 0 _CTS, and UART 0 _RTS. Applications processor  52  may have ports SPI, SIDEBAND, UART 2 _RXD, UART 2 _TXD, UART 1 _RXD, UART 1 _TXD, UART 1 _CTS, and UART 1 _RTS. 
     As shown by dashed lines  108 , a testing and/or debug device such as debug device  106  may be connected to the conductive lines and paths between baseband processor  52  and applications processor  54 . Typically, debug device  106  is used during laboratory testing (rather than during field testing) as connecting to the lines between processors  52  and  54  may include opening housing  12  of device  10  to gain access to the interior of device  10 . 
     USB signals from applications processor  54  may be routed over communications lines  100  to external devices. For example, VBUS power signals and D+ and D− USB data signals may be routed over lines  100 , through connectors  64  and  82 , and to an external accessory or device that connects to connector  88 . 
       FIG. 5  illustrates how a testing device such as testing device  110  may connect to device  10  through testing interface device  81  of  FIG. 4 . As shown in  FIG. 5 , testing device  110  may connect to a circuit under test (CUT) such as CUT  112  (e.g., a circuit such as baseband processor  52  and applications processor  54  of  FIG. 4 ). Testing device  110  may connect to CUT  112  through connectors  84 ,  86 , and  82  of test interface device  88  and through connector  64  of device  10  (as examples). 
     A conventional cellular telephone with multiplexer circuitry to support testing is shown in  FIG. 6 . As shown in  FIG. 6 , device  200  includes baseband processor  202  and applications processor  204  connected to external 30-pin connector  206 . The solid conductive paths in  FIG. 6  are active during normal operation and the dotted conductive paths are active during testing operations. 
     Baseband processor  202  includes a universal asynchronous receiver/transmitter (UART) communications bus formed from paths  206  and  207  between processors  202  and  204 . Path  207  runs through multiplexer  214  and is routed to baseband processor  202  during normal operation. Path  206  is also active during normal operation. 
     Paths  208 ,  210 ,  212 , and  216  form a UART communications bus between processors  202  and  204 . During normal operations, paths  208 ,  210 , and  212  are active and multiplexer  218  routes path  216  to baseband processor  202 . 
     During normal operation, paths  220  and  222  form a bidirectional UART communications bus between applications processor  204  and connector  206 . 
     During testing operations, paths  224  and  230  form a UART communications bus and paths  226  and  228  form a UART communications bus between connector  206  and baseband processor  202 . Multiplexer  218  routes path  228  of the UART communications bus to processor  202  and multiplexer  214  routes path  230  of the UART communications bus to processor  202  during testing operations. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.