Patent Publication Number: US-10789191-B2

Title: Real-time embedded system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/873,826, filed 4 Sep. 2013, and U.S. provisional application No. 61/873,796, filed 4 Sep. 2013, both of which applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     a. Technical Field 
     The instant disclosure relates to embedded systems, including operating systems and dynamic libraries for real-time embedded systems. 
     b. Background Art 
     Embedded systems are generally designed and implemented to fulfill a specific purpose. Accordingly, the hardware, software, and logic components of embedded systems may be generally simple and may be configured to perform a single intended function (or set of functions) with a minimum amount of processing power and memory to occupy a minimum amount of space and minimize the cost of the embedded system. Known embedded systems, to the extent they include software at all, thus generally implement static programming. Known embedded systems generally lack an operating system. 
     Embedded systems may be required to process data substantially in real-time. For example, global positioning system (GPS) systems may be included in a wide-ranging number of systems, including cell phones, navigation systems, and the like. Because the data from GPS systems may be used in conjunction with a rapidly-moving vehicle, for example, location data may need to be output by the GPS system in real-time to be useful. Numerous other embedded systems must operate substantially in real-time for usefulness (e.g., GPS), safety (e.g., aircraft systems), and other reasons. 
     SUMMARY 
     As increased processing power and memory have become available for a lower cost and in a smaller amount of space, greatly increased processing power and memory in embedded systems has become feasible. Yet still, embedded systems generally do not include operating systems. As a result, known embedded systems are limited in application and do not provide sufficient capability to easily service and update software. An operating system that is capable of maintaining real-time processing of data for an embedded system may cure the deficiencies of known embedded systems. Furthermore, embedded systems generally do not include dynamic library linking or loading. An embedded system that is configured for dynamic, network-based library linking and/or loading may cure deficiencies of known embedded systems. 
     An embodiment of a real-time operating system (OS) for an embedded system may be configured for asynchronous handling of input and output (I/O) operations. When application code is executing, the OS may be configured to register I/O interrupts and queue I/O operations. When no application code is executing, the OS may be configured to call appropriate interrupt handlers. As a result, the OS may maintain the real-time execution that may be required of applications on an embedded system while providing the flexibility and scalability offered by an operating system. 
     In a further embodiment, an OS for an embedded system may be configured for dynamic library linking and/or loading. That is, the embedded system, through the OS, may be configured to provide a single set of libraries for the applications, and the embedded system, through the OS, may be configured to acquire some or all of the set of libraries over a network connection. In an embodiment, the embedded system though the OS, may be configured to acquire libraries at runtime of the application that needs the libraries. By dynamically linking and loading libraries, the embedded system may provide increased functionality over what would otherwise be possible for the memory resources of the embedded system. 
     An exemplary method of operating an embedded system having one or more applications installed thereon in real-time may comprise a number of steps. The method may first include registering a respective interrupt handler for each of the one or more applications. The method may further include receiving a processing request from one of the one or more applications and servicing the processing request. The method may further include receiving an input or output (I/O) request from one of the one or more applications while servicing the processing request, waiting for servicing the processing request to complete, and, after servicing the processing request is complete, servicing the I/O request with the interrupt handler associated with the application from which the I/O request was received. 
     An embodiment of a real-time embedded system may include a processor and a memory storing instructions configured to be executed by the processor. The instructions may comprise an operating system configured to register a respective interrupt handler for each of one or more applications stored in the memory, receive a processing request from one of the one or more applications, and service the processing request. The operating system may be further configured to receive an input or output (I/O) request from one of the one or more applications, wait for servicing the processing request to complete, and, after servicing the processing request is complete, service the I/O request with the interrupt handler associated with the application from which the I/O request was received. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of an exemplary embodiment of a mesh network. 
         FIG. 2  is a block diagram view of an exemplary embedded system. 
         FIG. 3  is a block diagram illustrating exemplary portions of a memory of the embedded system of  FIG. 2 . 
         FIG. 4  is a block diagram illustrating respective exemplary associations of a plurality of applications installed on the embedded system of  FIG. 2  with a plurality of exception handlers. 
         FIG. 5  is a flow chart illustrating an exemplary method of operating the embedded system of  FIG. 2 . 
         FIG. 6  is a block diagram view of an exemplary embodiment of a virtualization system that may be implemented in the embedded system of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary Mesh Network. Referring to the drawings, wherein like reference numerals refer to the same or similar components in the various views,  FIG. 1  is a block diagram view of an exemplary mesh network  10 . The mesh network  10  may include one or more embedded systems  12   1 ,  12   2 ,  12   3 , . . . ,  12   N  (which may be referred to collectively as the embedded systems  12  or individually as an embedded system  12 ) and one or more general purpose computers  14   1 , . . . ,  14   M  (which may be referred to collectively as the general purpose computers  14  or individually as a general purpose computer  14 ), which may be collectively referred to as the mesh network devices  12 ,  14 . Each of the embedded systems  12  may include its own processing and memory resources, as discussed in greater detail below in conjunction with  FIG. 2 . Each of the general purpose computers  14  may also include its own processing and memory resources. In an embodiment, one or more of the general purpose computers  14  may include and/or may be replaced in the mesh network by a dedicated server, such as a library server, as described below. 
     As used herein, “embedded systems” refer to computing systems that are integrated (i.e., embedded) into larger systems and/or devices, which larger systems or devices include particular electrical, mechanical, and other components, with processing and memory resources and I/O components and peripherals specifically selected and configured to perform operations related to the particular electrical, mechanical, and other components of the larger system or device. Embedded systems  12  are different from general purpose computers  14 , which include processing and memory resources and I/O components and peripherals designed to accommodate a wide range of purposes or applications. 
     The embedded systems  12  and general purpose computers  14  may be configured to communicate with each other via one or more common communications protocols. For example, the embedded systems  12  and general purpose computers  14  may be configured to communicate over one or more of a Bluetooth protocol (e.g., substantially as described in the “Specification of the Bluetooth System: Covered Core Package version 4.0,” published 30 Jun. 2010, which is hereby incorporated by reference in its entirety as though fully set forth herein), such as a Bluetooth Low Energy (BLE) protocol, IEEE 802.11 (WLAN), IEEE 802.15 (WPAN), IEEE 802.16 (WiMAX), Global Grid Protocol (substantially as described and shown in co-pending U.S. patent application Ser. No. 13/506,051, which is hereby incorporated by reference in its entirety as though fully set forth herein), and/or another wireless networking protocol. The embedded systems  12  and general purpose computers  14  in the mesh network  10  may also be configured to communicate over known types of wired connections. The embedded systems may improve upon and deviate from the requirements and teachings of known specifications. For example, the BLE protocol requires a central node and peripheral nodes, limiting the scalability of a BLE network. In contrast, the system  10  does not require a central node. 
     Two or more of the mesh network devices  12 ,  14  may maintain persistent, continuous peer-to-peer connections with each other, in an embodiment. Conversely, two or more of the mesh network devices  12 ,  14  may open and close connections with each other intermittently and as necessary or desired, in an embodiment. 
     The mesh network devices  12 ,  14  may all form part of the same broader system, in an embodiment. The embedded systems  12  may all perform different functions from each other, or two or more of the embedded systems  12  may perform duplicate or redundant functions, in embodiments. For example only, the mesh network devices  12 ,  14  may form a part of an automated or partially-automated assembly line. In such an example, a first embedded system  12   1  may include a sensor for detecting a temperature or other performance variable of a first component, a second embedded system  12   2  may include and operate a display for viewing by workers on the assembly line, a third embedded system  12   3  may control an actuator for a second component on the assembly line, and a general purpose computer  14   1  may include programs for monitoring and directing numerous actuators and sensors on the assembly line, for example only. 
     Generally, as noted above, embedded systems  12  are designed for particular purposes, with programming instructions for performing one or more particular functions and processing and memory resources specifically configured for those particular functions. As a result, embedded systems  12  may be less expensive to produce and implement than general purpose computers  14 , but also may be more difficult to re-purpose. For example, in the assembly line example given above, a traditional embedded system that includes and operates a display may not provide the ability to alter the format of the display or information included on the display, for example. 
     In contrast, the embedded systems  12  of the mesh network  10  may include operating systems, thus providing the ability to install, remove, and modify applications installed on the embedded systems  12 . For example, returning to the assembly line example, the embedded system  12   2  that includes and operates a display may provide the ability to update or alter the contents or format of the display via an operating system, such as when components are added or removed from the assembly line. Furthermore, if the embedded system  12  includes sufficient memory resources, the embedded system  12  may provide the ability to install additional applications. 
     Exemplary Embedded System. 
       FIG. 2  is a block diagram view of an exemplary embodiment of an embedded system  12 . The embedded system  12  may include a processor  16 , a memory  18 , a transmit/receive radio  20 , and a component/sensor/actuator  22 . The memory  18  may include instructions configured to be executed by the processor  16 . The instructions may include an operating system (OS)  26 , in an embodiment, substantially as described herein and with additional functions and features known in the art. The memory may further comprise a read-only-memory (ROM)  24  and a read/write (R/W) memory  28 . 
     The component/sensor/actuator  22  may be or may include one or more components, sensors, and/or actuators that provide the underlying purpose of the embedded system  12 . That is, the processor  16 , memory  18 , and software applications installed in the memory  18  for operation by the OS  26  may be specifically selected and configured for operation with the component/sensor/actuator. 
     Two or more of the processor  16 , memory  18 , radio  20 , and component/sensor/actuator  22  may be incorporated into a single microcontroller, in an embodiment. Thus, the entire embedded system  12  may be implemented on a single integrated circuit (i.e., a system-on-a-chip), in an embodiment. 
     The memory  18  may, as noted above, include separate ROM  24  and R/W  28  portions. Alternatively, the memory  18  may include only a R/W portion  28 . The ROM portion  24  may include any type of “read-only” memory including, but not limited to, mask ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), and electrically-erasable programmable ROM (EEPROM). The R/W portion  28  may include, for example, any volatile or non-volatile memory type including, but not limited to, RAM, flash memory, and other NVRAM. 
     The OS  26  may be stored and/or executing in either or both of the R/W  28  and ROM  24  portions of memory  18 , in an embodiment, and/or to some other portion of the memory  18 . The OS  26  may be configured to write data to the R/W memory  28 , to read data from the R/W memory  28 , and to read data from the ROM  24 . In an embodiment in which the ROM  24  includes PROM, EPROM, EEPROM or other slowly-writeable memory, the OS may be further configured to write data to the ROM  24 . 
     The OS  26  may be configured to operate the embedded system  12  in real-time, in an embodiment. That is, the OS  26  may be configured to operate one or more applications installed on the embedded system  12  with negligible lag between data input to the embedded system  12  and data output from the embedded system  12 . For example, in an embodiment in which the component/sensor/actuator  22  includes a GPS antenna, and the embedded system  12  includes an application for determining and outputting a location of the embedded system  12  based on signals from GPS satellites, the operating system  26  may be configured to operate the application with negligible lag between receipt of GPS signals through the GPS antenna and output of a location. 
     The OS  26  may be configured, in an embodiment, to manage the hardware resources of the embedded system  12  (e.g., the processor  16  and the memory  18 ) for one or more applications installed in the memory  18 . The applications may be designed and/or implemented for one or more specific purposes, in an embodiment, such as the tasks or operations of a particular embedded system  12 . The OS  26  may also be configured for additional operations, as described herein. 
     Input/Output Operations. 
     In an embodiment, all I/O operations may be performed through the OS  26 , rather than by applications independently. As a result, the applications need not compete for resources, and no mutex or cross-thread code may be required, saving memory resources. Thus, in an embodiment, the OS  26  may lack mutex or cross-thread programming. 
     The OS  26  may be configured to transmit and receive data with the radio  20  in one or more communications protocols to enable a mesh network according to one or more such protocols, as noted above in conjunction with  FIG. 1 . In an embodiment, the OS  26  may enable up to 2 128  devices to be addressed (and therefore connected) in a mesh network, exceeding the number of devices permitted on most known mesh networks. 
     As noted above, the OS  26  may be configured to provide communications capabilities with other devices by operating the radio  20  of the embedded system  12 . To provide such communications capabilities (i.e., network I/O), the OS  26  may be configured to control (e.g., open and close) one or more different types of communications “sockets.” In an exemplary embodiment, the OS  26  may provide three different socket types that may be used for different types of transmissions. First, a “Reliable Socket” may be opened for persistent broadcasting and receiving of data with a particular device or system, for example. A Reliable Socket may be created by the OS  26  in response to either a connection request from a peer device in the mesh network or a connection response from a Listening Socket (described below). In a Reliable Socket transmission, if data is not received by the intended endpoint, an error may be registered by the OS  26 . A Reliable Socket may be used for transmission or receipt of large amounts of data, in an embodiment. The radio  20  may remain on for the duration of a Reliable Socket, in an embodiment. 
     A “Listening Socket” may be opened to listen for external devices, for example. Once an external device signal is discovered, in an embodiment, a Reliable Socket may be opened by the OS  26  for a persistent connection with that external device. 
     Finally, an “Unreliable Socket” may be opened for broadcasting undirected data. When an Unreliable Socket is open, the radio  20  may be turned on only when data is transmitted, in an embodiment. Thus, an Unreliable Socket may be preferred over a Reliable Socket, in an embodiment, when a particular destination for transmitted data is not required and/or reliable receipt of data is not required. 
     It should be noted that the communications details described herein (e.g., protocols, “socket” types, etc.) are exemplary in nature only and are not limiting except as expressly set forth in the claims. Thus, any number of different communications protocols, communications “sockets,” and other communications details may be added or altered without departing from the scope and spirit of the present disclosure. 
     Memory Portions and Addressing. 
     The operating system  26  may be configured to apportion memory  18 , write to memory  18 , read from memory  18 , and delegate those and other tasks to applications as needed.  FIG. 3  is a block diagram illustrating portions of the memory  18  that may be apportioned and maintained by the operating system  26 , in an embodiment. First, the OS  26  may maintain a portion of memory for one or more applications  30 . That is, the OS  26  may manage ROM  24  and R/W  28  memory resources for the storage and operation of applications  30 . 
     In an embodiment, the applications  30  may be configured to share a single set of libraries, rather than each of the applications  30  having its own set of libraries (i.e., dynamically-linked libraries). Thus, in an embodiment, the OS  26  may be configured to control access to the libraries by the applications  30  and to supplement the libraries as needed through dynamic library loading, as described below. The libraries may be stored in the applications  30  portion of memory  18 , in an embodiment. 
     Unlike many known embedded systems, the OS  26  may provide the capability for updating the firmware of the embedded system. In an embodiment, the OS  26  may maintain a staging area  32  in the memory  18  for firmware updates, where updates may be stored before being copied into executable memory. Additionally, in an embodiment, the OS  26  may maintain a system recovery portion  34  in the memory  18 , where a configuration of the OS  26  and installed applications  30  may be maintained in case of a crash during a software install or update. The OS  26  may be configured to periodically (e.g., automatically and/or responsive to user command) update the system recovery portion  34  of the memory  18  to match the current configuration. 
     In an embodiment, the OS  26  may be configured to address one or more portions of the memory  18  using 128-bit addressing, compressed to 64-bit. Four-byte connection handles may be used, in an embodiment. Of course, the OS  26  is not limited to such address and connection handle lengths. In different embodiments, different lengths may be used as appropriate. 
     Applications Registration. 
     In order to properly handle the I/O calls of one or more applications  30 , the OS  26  may be configured to register each application  30  installed on the embedded system  12  and to register an interrupt handler for each application  30 .  FIG. 4  is a block diagram illustrating associated applications and interrupt handlers registered with the OS. In an embodiment, the OS may register a plurality of applications  30   1 ,  30   2 , . . . ,  30   K , each of which may register a respective associated interrupt handler  36   1 ,  36   2 , . . . ,  36   K  with the OS  26 . The OS may register applications  30  and interrupt handlers  36  on startup of the embedded system  12 , in an embodiment. Application  30  and interrupt handler  36  registration may additionally or alternatively occur when the OS  26  or firmware is updated, or when the embedded system recovers from a crash. Following registration, the OS  26  may maintain a registry of applications and interrupt handlers, which registry may be referred to for servicing I/O requests from the applications, as described below in conjunction with  FIG. 5 . 
     Asynchronous Real-Time Operation. 
     The OS  26  may be configured for asynchronous handling of input and output (I/O) operations. When application code is executing, the OS  26  may be configured to register I/O interrupts and queue I/O operations. When no application code is executing, the OS may be configured to call appropriate interrupt handlers  36 . In an embodiment, the OS  26  and applications  30  implemented through the OS  26  may lack synchronous interrupt calls. Accordingly, for some or all I/O operations, the OS  26  may be configured to advance to the next processing task before a commanded I/O operation has been completed. 
       FIG. 5  is a flow chart illustrating a method  40  of operating an embedded system having one or more applications installed thereon, such as the embedded system  12  shown in  FIG. 2 , in real time. The method  40  may be performed by the operating system  26  in the embedded system  12  of  FIG. 2 . The method  40  generally implements asynchronous I/O handling by queuing I/O operations until application code is complete, rather than interrupting the implementation of application code to service I/O requests, and continuing to service processing requests while I/O operations are serviced by appropriate interrupt handlers. The method  40  is illustrated and described with reference to an embodiment having a single processing thread executing on a single processing core. In another embodiment, in which multiple processing cores are included in the embedded system, each of which may each execute its own processing thread, the method  40  may include different or additional steps. 
     The method  40  may begin with receiving a processing request  42  or receiving an I/O request  44 . For either request type, the method may advance to determining if the processing thread is busy  46 ,  48 —i.e., determining if the processing thread is executing application code from an application installed on the embedded system to service a processing request from that application. If the thread is busy, the method  40  may advance to queuing the request until the thread is not busy  50 ,  52 . 
     If the thread is not busy, or once the thread is not busy, the method  40  may advance to determining if there is an I/O request in the queue  54 ,  56 . If there is an I/O request in the queue, then the method  40  may advance to servicing a queued I/O request  58 ,  60 . An I/O request received from a particular application may be serviced with an interrupt handler that was registered with that application during the OS boot sequence or at another time, in an embodiment. As described above with reference to  FIG. 4 , associations between applications and interrupt handlers may be stored in a registry. Once servicing the I/O request is complete (i.e., once the thread is no longer busy), the method  40  may return to determining if there is an I/O request in the queue  54 ,  56 . In an embodiment, the method  40  may return to determining if there is an I/O request in the queue  54 ,  56  before servicing the previous I/O request is complete, for asynchronous operation. 
     If there is not an I/O request in the queue, and the request is an I/O request, the method  40  may advance to servicing the request  62 . If there is not an I/O request in the queue, and the request is a processing request, the method  40  may advance to determining if there is a processing request in the queue  64 . If there is a processing request in the queue, the method  40  may advance to servicing the queued processing request  66 . If there is not a processing request in the queue, the method  40  may advance to servicing the received request  62 . Once the received request is serviced—either immediately or from the queue—the embedded system may enter a sleep mode, in an embodiment, waiting for further I/O or processing requests. 
     Because the OS  26  may delay servicing of I/O calls until application code is not running, applications running on the OS  26  may be coded such that individual functions (i.e., processing required for individual processing requests) are limited in duration. For example only, in an embodiment, application functions may be coded such that each processing request may be completed in two milliseconds or less. Such timing preferences may be feasible given the predictable processing and memory resources of the embedded system. That is, because the available processing and memory resources of the embedded system executing an application may be known to the programmer in advance, the applications may be written so that processing requests may be completed within a desired or required amount of time. 
     The steps of the method  40  are exemplary in nature only and are not limiting. Instead, there are numerous methods by which an operating system may perform asynchronous I/O with queued processing requests. For example, although the method is illustrated and described herein as giving preference to servicing I/O operations over servicing processing operations, such preference is not required except as explicitly set forth in the claims. Many other changes may be made to the arrangement and content of the steps of the method  40  without departing from the scope and spirit of the present disclosure. 
     The OS  26  may be configured for use with a processor  16  having a single core, two cores, three cores, etc. In a multi-core embodiment, a single core may be configured to queue and service I/O interrupts, and additional cores may be dedicated to data processing operations delegated by the first core. Thus, in an embodiment, the first core may receive all I/O and processing requests from applications, perform certain processing tasks, and delegate processing requests to the second and other cores as needed. The second and other cores, in turn, may be able to communication only with the first core, and may not be able to communicate with the applications or I/O devices themselves. 
     Transmission-Based Distance Determination. 
     In addition to the more general capabilities and functions that may be provided by the OS  26  described above, the OS may provide numerous other services that may be useful in a mesh network or otherwise. As part of the data transmission capabilities of the system, the OS  26  may be configured to determine and/or approximate the distance between an embedded system  12  on which the OS  26  is installed and another device with which the embedded system  12  is communicating wirelessly. A distance estimate may be made according to the frame size (in time) and the number of packets retransmitted—because the number of packet retransmissions that are needed correlates to the distance between two devices, the OS  26  may associate a given number of retransmitted packets for a given frame size with a particular distance. Additionally or alternatively, this association may be performed by an application running on the OS  26 , with access to transmission information (e.g., frame size, number of packet retransmissions) provided to the application or enabled by the OS  26 . Accordingly, an embedded system  12  may be configured to determine a distance between itself and a device with which it is in wireless communication by counting the number of packets that need to be retransmitted to completely transmit a given message and associating that number with a distance. The number of packets that must be retransmitted may be associated with a distance according to a look-up table or formula, in an embodiment. 
     Virtualization. 
     The OS  26  may additionally enable virtualization, in an embodiment. The virtualization may be performed at the kernel level (i.e., “ring zero” of a hierarchical security scheme), as in some known virtualization methods, or it may be performed in software, by the OS  26 , at an outer ring of the security scheme. Thus, the OS  26  may be configured to provide virtualization of a second user space, apart from the space provided by the OS  26  itself, that may appear to a user to be independent of the OS  26 . However, because the OS  26  may maintain exclusive access to the kernel, implementation of software-based virtualization may be more secure, as the second user space need not be given separate access to the kernel, as in many known virtualization methods. 
       FIG. 6  is a block diagram view of a virtualization system  70 . The virtualization system  70  illustrated in  FIG. 6  may be implemented through one or more embedded systems  12  of  FIGS. 1 and 2 , for example, though it is not limited to implementation on embedded systems. Referring to  FIGS. 2 and 6 , the virtualization system  70  may include a kernel  72 , the processor  16 , the memory  18 , one or more I/O devices  74  (which may include the radio  20  and component/sensor/actuator  22 ), one or more applications  30 , and a virtual machine  76 . The virtual machine may respectively include a virtual kernel  78  and one or more applications  80 . 
     The kernel  72  may manage the resources of the system—i.e., the processor  16 , memory  18 , and I/O devices  74 —for use by the applications  30 . For example, the kernel  72  may manage I/O requests from the applications  30  and generate data processing instructions for the processor  16 , memory  18 , and I/O devices  74 . The kernel  72  may be a part of the operating system  26  (see  FIG. 3 ), and thus may perform I/O tasks substantially as described herein. 
     Referring to  FIGS. 3 and 6 , the virtual machine  76  may be created and provided by the operating system  26 . The virtual machine may be created under a virtualization engine such as, for example only, V8, the JavaScript virtual machine engine commercially available from Google, Inc., or the .NET framework commercially available from Microsoft, Inc. A virtual machine  76  may be created to virtualize the entire OS  26  (or a substantial portion thereof), in an embodiment. Alternatively, a virtual machine  76  may be created for each application  80  to be run in a virtualized environment. 
     The virtual machine  76  may execute one or more applications  80 , which may be the same applications  30  as those stored in the embedded system memory  18 , in an embodiment. To execute the virtual machine application(s)  80 , the virtual machine  76  may be provided with a software-based virtual kernel  78  that services I/O calls from the application(s)  80  running on the virtual machine  76 . The virtual kernel  78  may, among other features, distinguish the system  70  from known virtualization systems. 
     The virtual kernel  78  may be provided with a privilege level customized to the needs of the virtual machine  76 . For example, the virtual kernel  78  may have heightened privileges relative to the applications  30 , but lower privileges relative to the kernel  72 . The privileges granted to a virtual kernel  78  may be determined at the time of implementation of the virtual machine  76 , in an embodiment. For example, in an embodiment, the virtual kernel  78  may be configured to access hardware resources (e.g., the processor  16 , memory  18 , and I/O devices  74 ) through the kernel  72 , rather than having direct access to the hardware resources. Alternatively, the virtual kernel  78  may be configured for direct access to one or more hardware resources, but for accessing some other resources through the kernel  72 . 
     In an embodiment, the virtual machine  76  may be implemented on a first embedded system or other system and hosted by a second embedded system or other system. Thus, the second system may be provided access to the hardware resources and, if desired, applications  30  of the first system. Such an arrangement may provide several advantages. First, a number of embedded systems or other systems may execute common applications through virtual machines accessed by those systems without requiring the applications to be installed on those systems. Second, applications can be run by a system which the system would ordinarily not have resources to install and/or execute. Third, through the use of the virtual kernel, virtual machines may be implemented on one or more machines without the security risk inherent in directly exposing the hardware resources of the host machine to the virtual machine. Fourth, separate privilege levels may be created for different applications executing on a virtual machine. For example, if a separate virtual machine (and, thus, separate virtual kernel) is created for each application to be run in a virtualized environment, each virtualized kernel may be given privileges customized to the needs of its application. 
     Dynamic Library Linking and Loading. 
     Referring to  FIG. 3 , an embedded system  12  may be configured for dynamic library linking. As noted above, known embedded systems generally lack operating systems. Accordingly, known operating systems lack the capability for dynamic library linking. In contrast, an embedded system  12  according to the present disclosure may enable dynamic library linking by providing an OS  26 . Accordingly, numerous applications installed on the embedded system  12  may share a single set of libraries, conserving the memory resources of the embedded system  12 . As noted above, the OS  26  may control access to the libraries by the applications  30 . 
     In addition to dynamic library linking, an embedded system  12  may be configured for dynamic library loading, also enabled by the OS  26 . Dynamic library loading may involve the embedded system  12  acquiring libraries (or portions thereof) over a network connection, on demand, as needed by applications  30  stored in memory  18 . Thus, the memory resources of the embedded system  12  may be further conserved, and the library size available to the applications increased, by storing libraries remotely and loading them on to the embedded system  12  as needed. 
     Referring to  FIG. 1 , an embedded system  12  may be configured to retrieve libraries, and/or portions thereof, on demand from one or more general purpose computers  14  (which may, as noted above, include or be replaced with a dedicated server). Accordingly, in an embodiment, the mesh network  10  may include a dedicated library server. The dedicated library server, or a general purpose computer  14  in the network  10 , may be configured to store a plurality of libraries with wide applicability. Libraries may be loaded as necessary by an embedded system  12  over the network connection between the dedicated library server or general purpose computer  14  and the embedded system  12 . 
     In an embodiment, one or more of the embedded systems  12  may be configured to access and download libraries (or portions thereof) over the mesh network  10  at runtime of the application that uses a given library or portion of a library. Accordingly, the memory  18  of an embedded system  12  (see  FIG. 2 ) may include less storage capacity than would be necessary if the embedded system  12  needed to store all libraries for all possible applications that are or may be installed on the embedded system  12 . Furthermore, dynamic library loading advantageously allows libraries on an embedded system and/or on a library server or general purpose computer  14  to be updated, supplemented, replaced, etc. with improved libraries or improved library portions. 
     In an embodiment of the mesh network  10 , a set of libraries may be stored in a dedicated library server or general purpose computer  14 , remote from the embedded systems  12 , for access by all of the (e.g., a plurality of) embedded systems  12  on the network  10 . Each of the embedded systems  12  may be configured for dynamic library linking and/or loading. In the same or another embodiment, an embedded system  12  may be configured to dynamically load portions of libraries from peer embedded systems  12 . Thus, an embedded system  12  according to the present disclosure may be further configured to share library portions stored in its memory with other embedded systems. 
     Directed Broadcast Routing. 
     An embedded system  12  may also be configured for a novel method of data transmission to a specific other embedded system  12 , which method may be referred to herein as directed broadcast data routing. Referring to  FIG. 1 , the method may begin with a step that includes an originating or master device (e.g., the general purpose computer  14   1 ) establishing communication with an initial embedded system (e.g., embedded system  12   1 ), which may the closest-in-distance embedded system  12  in the mesh network  10  to the master device. 
     The message transmitted in the establishing communication step may be the underlying intended transmission, in an embodiment. That is, the message transmitted in the establishing communication may be or may include the entirety of the message that is intended for the desired embedded system  12 . Alternatively, the message transmitted in the establishing communication step may be or may include a portion of the entirety of the message intended for the desired embedded system  12 . Alternatively, the message transmitted in the establishing communication step may lack any substantive data intended for the desired embedded system  12 , and may instead include a handshake message or the like. 
     The method may continue to a step that includes the master device determining if the initial embedded system  12   1  is the desired embedded system  12  (e.g., is the embedded system  12  with which communication is desired). If the initial embedded system  12   1  is the embedded system  12  with which communication is desired, the method may terminate. 
     If, instead, the initial embedded system  12   1  is not the embedded system with which communication is desired by the master device, the method may continue to a step that includes the master device taking control the I/O interface of the initial embedded system  12   1 . The master device may take control of the I/O interface of the initial embedded system  12   1 , in an embodiment, by accessing the background debug mode of the initial embedded system  12   1 . 
     The method may further include a step that includes the master device controlling the radio of the embedded system  12   1  to establish communication with a next embedded system  12  (e.g., embedded system  12   2 ), which may be the next-closest-in-distance embedded system  12  in the mesh network  10 . The step of establishing communication with a next embedded system  12  may include the transmission of the substance of the message that was transmitted to establish communication with the initial embedded system  12 , in an embodiment. The master device may then communicate with the next embedded system  12   2  via the initial embedded system  12   1 . 
     The method may then include a step that includes determining if the next embedded system  12   2  is the desired embedded system  12 . If the embedded system  12   2  is the embedded system  12  with which communication is desired, the method may terminate. 
     If, instead, the next embedded system  12   2  is not the embedded system with which communication is desired by the master device, the steps of taking control the I/O interface of the embedded system  12 , controlling the radio of the embedded system  12  to establish communication with the next embedded system  12  (e.g., embedded system  12   3 , then the next embedded system  12 , through embedded system  12   N ), and determining if the next embedded system  12  (i.e., the embedded system  12  with which communication is most recently established) is the desired embedded system  12  may repeat until the desired embedded system  12  is found. At each iteration of the steps (i.e., for each next embedded system  12 ), communications between the master device and the embedded system  12  with which communication is most recently established may be routed through each previous embedded system  12  with which communication was established, in an embodiment (i.e., such that, in the sequence described above, communications between the master device and embedded system  12   3  would go through embedded systems  12   1  and  12   2 ). 
     It should be noted that the description above of the general purpose computer  14   1  as the master device is for ease of description only. The described method may find use with any device in any mesh network as the master device, including an embedded system  12 . Furthermore, it should be noted that the master device in the method is the device from which a data transmission originates and which desires to transmit the data to a specific other device in the mesh network  10 . 
     Directed broadcast data routing may advantageously remove the need to determine a routing table for the mesh network  10  or to store a routing table in any device in the mesh network  10 . Furthermore, each “hop” in the method from one device to the next may add only a small amount of data to the transmitted data (e.g., 3-5 bytes per hop, in an embodiment), so hopping over numerous embedded systems  12  may be possible even with limited memory resources in the embedded systems  12 . 
     Blind Data Transfer. An embedded system  12  may also be configured for efficient multi-device data transfer. The efficient data transfer method may be used for blind data transfers—that is, data transfers when no particular recipient is intended. Such blind transfers may find use, in an embodiment, when data is to be transferred to the entirety of a given mesh network, for example. 
     In an embodiment, the data transfer method may include a source device (referring to  FIG. 1 , an embedded system  12  or general purpose computer  14  may be the source device) transmitting the desired data, or a portion thereof. The transmission may include the underlying data and a maximum hop count. Each embedded system that detects the transmission may accept the data, decrement the hop count, and re-transmit the data. Accordingly, the data may rapidly propagate through a large mesh network without the need to store addressing information. 
     The data transfer method, like other methods and processes described herein, may be programmed in the OS of the embedded system (i.e., OS  26 , see  FIG. 2 ). Accordingly, the OS  26  may be configured to perform the steps and processes of the blind data transfer method of the present disclosure. 
     In an embodiment, the source device may divide the total data to be transferred (e.g., a single file) into smaller component parts and transmit those component parts separately. Accordingly, different component parts of the data may propagate through the mesh network at different times and along different paths. 
     Although a number of embodiments have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the sprit or scope of this disclosure. For example, all joinder referenced (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joined references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims. 
     Various embodiments are described herein to various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims. 
     Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment,” or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment,” or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional. 
     Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by referenced herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.