Patent Publication Number: US-2023140987-A1

Title: Wireless transceiver resynchronization options during wireless management of subsystems

Description:
BACKGROUND 
     As new electronic devices are developed and integrated circuit (IC) technology advances, new IC products are commercialized. One example IC product for electronic devices is a communication circuit with a wireless transceiver. There are many different wireless communication protocols and related wireless transceivers to support different ranges of wireless data transfer, different levels of security, frequencies used, and/or other variations. In some systems, wireless transceivers may be added to simplify wiring and facilitate replacement or repair of subsystem components/modules. For example; there are systems with a controller and multiple subsystems, where the controller and each of the subsystems need to communicate with each other. Use of wires between the controller and each subsystem as well as wires between subsystems is problematic when space is limited. Such wires make installation; removal, and/or replacement of each subsystem more challenging (e.g., the wires related to each subsystem need to be connected during installation, disconnected when servicing/removing, and reconnected after servicing/removing, which is difficult when space is limited). In this example, the addition of wireless transceivers would simplify the wiring between the controller and the subsystems and/or the wiring between the subsystems with the above-noted benefits. However, the addition of wireless transceivers may prevent compliance with safety standards of a system. 
     One example system that could benefit from wireless transceivers is an electric vehicle with a battery management system (BMS), resulting in a wireless BMS (WBMS). However, according to standard ISO 26262, battery monitoring devices need to provide Automotive Safety Integrity Level D (ASIL-D). There are two solutions for ASIL-D compliance: 1) the battery monitoring device can use separate measurement chains for temperature, voltage, and other events; or 2) the battery monitoring device can have built in tests to ensure that the probability of a failure meets the standard&#39;s requirements. In either instance, data must be transferred between a main controller and the subsystems of the WBMS within a certain time interval to ensure the safety of the system. The current standard specifies this interval as less than 100 ms. If a wireless transceiver loses synchronization with an established network, the probability of non-compliance with such safety standards increases. 
     SUMMARY 
     In at least one example, a communication circuit comprises network formation circuitry configured to establish a wireless network between a primary wireless transceiver and a secondary wireless node. The communication circuit also comprises data transfer circuitry configured to perform data transfers between the primary wireless transceiver and the secondary wireless transceiver. The communication circuit further comprises resynchronization circuitry configured to resynchronize the secondary wireless transceiver with the established wireless network within a target time interval. 
     In another example, a system comprises: a primary wireless transceiver adapted to be coupled to a controller of the system; and a secondary wireless transceiver adapted to be coupled to a subsystem of the system. The primary wireless transceiver and the secondary wireless transceiver are configured to establish a wireless network. The secondary wireless transceiver is configured to: identify a resynchronization trigger; and perform resynchronization with the established wireless network within a target time interval in response to the identified resynchronization trigger. 
     In yet another example, a method is performed by a communication circuit between a controller and a subsystem. The method comprises: establishing a wireless network with another communication circuit to transfer data between the controller and the subsystem; identifying a resynchronization trigger; and performing resynchronization with the established wireless network within a target time interval in response to the identified resynchronization trigger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram of a system in accordance with an example embodiment. 
         FIG.  2    is a block diagram of another system in accordance with another example embodiment. 
         FIG.  3 A  is a diagram of a wireless management network protocol in accordance with an example embodiment. 
         FIG.  3 B  is a diagram of transceiver resynchronization using configuration channels in accordance with an example embodiment. 
         FIG.  4    is a diagram of a Wireless Battery Management System (WBMS) in accordance with an example embodiment. 
         FIG.  5    is a block diagram of a battery management unit (BMU) and a cell monitoring unit (CMU) in accordance with an example embodiment. 
         FIG.  6    is a diagram of a communication circuit in accordance with an example embodiment. 
         FIG.  7    is a flowchart of a communication circuit method in accordance with an example embodiment. 
     
    
    
     The same reference number is used in the drawings for the same or similar (either by function and/or structure) features. 
     DETAILED DESCRIPTION 
     Some example embodiments include a communication circuit with a wireless transceiver configured to perform resynchronization with an established wireless network as needed. The communication circuit may be an integrated circuit (IC) or other circuit. In some example embodiments, the wireless transceiver is part of a system with a controller in communication with subsystems via communication circuits that support wireless communications. In some example embodiments, the system includes a primary wireless transceiver and secondary wireless transceivers. The primary wireless transceiver is in communication with the controller (e.g., via a wired coupling), while each secondary wireless transceiver is in communication with a respective subsystems (e.g., via respective wired couplings). In operation, the primary wireless transceiver and the secondary wireless transceivers are configured to establish a wireless network and transfer data to each other as needed. Each secondary wireless transceiver is also configured to: identify a resynchronization trigger; and perform resynchronization with the established wireless network within a target time interval in response to the identified resynchronization trigger. The resynchronization options vary depending on whether a given secondary wireless transceiver is in an active wireless transceiver state (sometimes referred to herein as an active state) or a reset wireless transceiver state (sometimes referred to herein as a reset state). 
     In one example embodiment, the system is an electric vehicle and the communication circuits are part of a wireless subsystem management system such as a wireless battery management system (WBMS). For a WBMS, the primary wireless transceiver is part of a primary communication circuit included with a battery management unit (BMU) of the WBMS. The BMU includes, for example, a printed circuit board (PCB) with the controller and the primary communication circuit coupled via a wired coupling. Also, each secondary communication circuit is part of a respective cell monitor unit (CMU) of the WBMS. Each CMU includes, for example, a PCB with a respective secondary communication circuit and a respective monitor circuit coupled via a wired coupling. Each CMU may additionally include other components such as an adjustment controller to adjust operations of a monitored electrical component (e.g., a rechargeable battery). Each CMU is thus configured to monitor a monitored electronic component, provide data to the BMU, receive adjustment control signals or instructions back from the BMU, and adjust a respective monitored electronic component based on the adjustment instructions. 
     With the resynchronization options described herein, the communication circuits for a system with a controller and subsystems provide a wireless interface to facilitate wiring, replacement, and/or repair of the subsystems. In some example embodiments, each of the subsystems has similar components (e.g., a PCB, a communication circuit that supports wireless communications, and other components coupled to the communication circuit) and functionality. For example, in a WBMS, each of the subsystems includes a respective PCB with a communication circuit and a CMU configured to perform monitoring and/or adjustments with regard to a respective battery cell. Without limitation to their particular functionality, individual subsystems or related modules are replaceable in some example embodiments (i.e., the subsystems or related modules are modular in that they can be easily attached, detached, and/or replaced as needed). Together, the controller and the subsystems of a WBMS control charging of multiple battery cells (e.g., coupled in series and/or in parallel) and detect if a particular battery cell or related subsystem is not working properly. In some example embodiments, wireless communications between a controller and the subsystems of a system comply with a target time interval. Without limitation, the target time interval may be related to a safety standard (e.g., an automotive safety standard). 
       FIG.  1    is a block diagram of a system  100  in accordance with an example embodiment. In some example embodiments, the system  100  is an electric vehicle with battery management subsystems, or another system with subsystems. As shown, the system  100  includes a controller  102  in communication with subsystems  112 A- 112 N via wireless communication channels (not shown). To support such communications between the controller  102  and the subsystems  112 A- 112 N, the controller  102  is coupled via a wired coupling  105  to a primary communication circuit  104 . The controller  102  is also coupled to other components  132  of the system  100  via a communication interface  130 . The communication interface  130  may be a controller area network (CAN) or other communication interface. Also, each of the subsystems  112 A- 112 N includes a respective secondary communication circuit  114  in communication with the primary communication circuit  104  via respective wireless communication channels. As shown for the subsystem  112 A, the secondary communication circuit  114  is coupled to a respective monitor circuit  122  via a wired coupling  115 . The controller  102  is this able to communicate with each respective monitor circuit  122  of the subsystems  112 A- 112 N and vice versa via a combination of wired and wireless communications. Such communications may be for battery management system (BMS) operations or management of another type of monitored electrical component  126 . 
     Adding wireless communications to the system  100  using the primary communication circuit  104  and each secondary communication circuit  114  facilitates repair and/or replacement of some or all of the components of the subsystems  112 A- 112 N. However, such wireless communications may introduce unacceptable delays if synchronization between a primary wireless transceiver  106  of the primary communication circuit  104  and a secondary wireless transceiver  116  of a given secondary communication circuit  114  is lost. Accordingly, in the example of  FIG.  1   , the primary communication circuit  104  and/or each secondary communication circuit  114  is configured to perform resynchronization operations within a target time interval as needed (e.g., if synchronization with an established network is lost). With the resynchronization operations, wireless data transfers between the controller  102  and each of the subsystems  112 A- 112 N (via the primary communication circuit  104  and each secondary communication circuit  114 ) are supported, while ensuring these wireless data transfers are performed within a target time interval even if synchronization is lost. 
     In operation, each of the subsystems  112 A- 112 N uses its respective monitor circuit  122  to monitor parameters of a monitored electrical component  126 . In some example embodiments, the monitored electrical component  126  is a rechargeable battery. Without limitation, the monitored parameters may include a voltage across the monitored electrical component  126  and/or a current through the monitored electrical component  126 . The monitored parameters (or related values) are transferred to the controller  102 , which analyses the monitored parameters (or related values) and determines whether any adjustments are needed. If adjustments are needed for a given subsystem, the controller  102  provides adjustment control signals to the given subsystem. As shown, each of the subsystems  112 A- 112 N includes a respective adjustment controller  124 , which is configured to adjust operations of a respective monitored electrical component  126  based on any adjustment control signals received from the controller  102 . 
     In some example embodiments, the primary communication circuit  104  is an IC with a primary wireless transceiver  106 . The primary wireless transceiver  106  includes circuitry and related programming/instructions to support a wireless network stack. As shown, the primary wireless transceiver  106  includes network formation circuitry  108  configured to establish a wireless network between the primary wireless transceiver  106  in communication with the controller  102  and a secondary wireless transceiver (e.g., the secondary wireless transceiver  116  in  FIG.  1   ) in communication with or part of a given subsystem. The primary wireless transceiver  106  also includes data transfer circuitry  110  configured to perform data transfers between the primary wireless transceiver  106  and a secondary wireless transceiver (e.g., the secondary wireless transceiver  116  in  FIG.  1   ). As shown, the primary wireless transceiver  106  further includes resynchronization circuitry  111 . The resynchronization circuitry  111  is configured to support resynchronization of a secondary wireless transceiver (e.g., the secondary wireless transceiver  116  in  FIG.  1   ) with an established wireless network within a target time interval. 
     In the example of  FIG.  1   , the secondary communication circuit  114  may be an IC that includes the secondary wireless transceiver  116 . The secondary wireless transceiver  116  includes circuitry and related programming/instructions to support a wireless network stack. As shown, the secondary wireless transceiver  116  includes network formation circuitry  118  configured to establish a wireless network between the secondary wireless transceiver  116  in communication with a given monitor circuit  122  and the primary wireless transceiver  106  in communication with the controller  102 . As another option, the secondary wireless transceivers of different subsystems may communicate wirelessly with each other as part of an established wireless network. The secondary wireless transceiver  116  also includes data transfer circuitry  120  configured to perform data transfers between the secondary wireless transceiver  116  and the primary wireless transceiver  106 . As another option, data transfers occur between the secondary wireless transceivers of different subsystems. 
     As shown, the secondary communication transceiver  116  further includes the resynchronization circuitry  121 . The resynchronization circuitry  121  is configured to resynchronize the secondary wireless transceiver  116  with an established wireless network within a target time interval. Example resynchronization operations include identifying if the secondary communication transceiver  116  is in an active state or a reset state. If the secondary communication transceiver  116  is in the active state, resynchronization options may include using a configuration channel or data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. If the secondary wireless transceiver  116  is in the reset state, resynchronization options may include: scanning multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronizing the secondary wireless transceiver  116  with the established wireless network based on the identified active channel. 
     In some example embodiments, resynchronization circuitry (e.g., the resynchronization circuitry  121 ) is configured to: identify the secondary wireless transceiver as being in an active state or a reset state; and if the secondary wireless transceiver is identified as being in an active state, use a configuration channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. In such example embodiments, the resynchronization circuitry is configured to: switch to a next available configuration channel within the frequency hopping schema in response to the secondary wireless transceiver losing synchronization with the established wireless network; and wait in a receive mode at the next available configuration channel until a next packet is received from the primary wireless transceiver. 
     In some example embodiments, resynchronization circuitry (e.g., the resynchronization circuitry  121 ) is configured to: identify the secondary wireless transceiver as being in an active state or a reset state; and if the secondary wireless transceiver is identified as an active state, use a data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. In such example embodiments, resynchronization circuitry is configured to: estimate a number of missed superframes of the established wireless network in response to the secondary wireless transceiver losing synchronization with the established wireless network; and use the estimated number of missed superframes to resynchronize the secondary wireless transceiver with the established wireless network. A superframe is discussed below. 
     In some example embodiments, resynchronization circuitry (e.g., the resynchronization circuitry  121 ) is configured to: identify the secondary wireless transceiver as being in an active state or a reset state; if the secondary wireless transceiver is identified as being in a reset state, scan multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronize the secondary wireless transceiver with the established wireless network based on the identified active channel. In such example embodiments, the resynchronization circuitry is configured to scan all channels within the frequency hopping schema within the target time interval. As another option, scanning the channels within a frequency hopping schema of the established wireless network to identify an active channel may be performed when the secondary wireless transceiver is identified as being in an active state. 
       FIG.  2    is a block diagram of another system  200  in accordance with an example embodiment. With the system  200 , wireless management of subsystems  222 A- 222 N (examples of the subsystems  112 A- 112 N in  FIG.  1   ) is provided with resynchronization options within a target time interval as described herein. In  FIG.  2   , the system  200  includes a lower voltage domain  202  (e.g., 12, 24, or 48 volts) with control circuitry  204 . Meanwhile, the subsystems  222 A- 222 N are in a higher voltage domain  203  (e.g., several hundreds of volts) compared to the control circuitry  204 . As shown, the control circuitry  204  includes a microcontroller  102 A (an example of the controller  102  in  FIG.  1   ) and a primary communication circuit  104 A (an example of the primary communication circuit  104  in  FIG.  1   ). The control circuitry  204  may also include a communications bridge  208  between the microcontroller  102 A and the primary communication circuit  104 A. In the example of  FIG.  2   , a main electronic control unit (ECU)  250  for the system  200  is coupled to the control circuitry  204  via a communication interface  130 A (an example of the communication interface  130  in  FIG.  1   ). In operation, the primary communication circuit  104 A is configured to perform primary wireless transceiver operations, including resynchronization operations for an active wireless transceiver and/or a reset wireless transceiver as described herein. 
     As shown, the subsystem  222 A includes a module  230 A. The module  230 A may include a PCB with a secondary communication circuit  114 A (an example of the secondary communication circuit  114  in  FIG.  1   ), a monitor circuit  122 A (an example of the monitor circuit  122  in  FIG.  1   ), and an adjustment controller  124 A (an example of the adjustment controller  124  in  FIG.  1   ). The module  230 A is coupled to a monitored electrical component  126 A (an example of the monitored electrical component  126  in  FIG.  1   ). The subsystems  222 B- 222 N each include a respective module  230 B- 230 N coupled to a respective monitored electrical component  126 B- 126 N. In some example embodiments, the monitored electrical components  126 A- 126 N are rechargeable batteries or other components with a variable status. Without limitation, each the modules  230 B- 230 N include the same type of components (e.g., a secondary communication circuit, a monitor circuit, and an adjustment controller) as the module  230 A. 
     In  FIG.  2   , the secondary communication circuit  114 A is configured to perform secondary wireless transceiver operations, including active wireless transceiver resynchronization operations and/or reset wireless transceiver resynchronization operations as described herein. Also, the monitored electronic components  126 A- 126 N may be coupled together to provide a combined function. As shown, the system  200  includes switches  240 ,  242 , and component  245 . In some example embodiments, the component  245  is a motor/engine. In this case, closing the circuit at switches  240  and  242  results in current flowing through the engine/motor to operate a vehicle. When the vehicle is parked or turned off, the switches  240  and  242  are open. In the example of  FIG.  2   , the switches  240  and  242  are controlled by a control signal  252  from the microcontroller  102 A. The control signal  252  is conveyed to the switches  240  and  242 , for example, via interface  216 . In the example of  FIG.  2   , the microcontroller  102 A may also receive a current sense signal  248  via interface  218 , where the current sense signal  248  is generated from a loop  244  or related sensor  246 . 
     In operation, the primary communication circuit  104 A is configured to send data to and receive data from the microcontroller  102 A via a wired coupling (e.g., the communications bridge  208 ). The primary communication circuit  104 A is also configured to send data to and receive data from one or more of the secondary communication circuits  114 A- 114 N via respective wireless communication channels (not shown). In some example embodiments, resynchronization operations are performed as needed. As an example, the primary communication circuit  104 A may support configuration channels within a frequency hopping schema of an established wireless network. Such configuration channels enable secondary communication circuits that lose synchronization with an established wireless network to resynchronize within a target time interval. 
     Also, each of the secondary communication circuit  114 A- 114 N is configured to send data to and receive data from a respective monitor circuit  122 A- 122 N via a respective wired couplings  115 A- 115 N (examples of the wired coupling  115  in  FIG.  1   ). Each of the secondary communication circuits  114 A- 114 N is also configured to send data to and receive data from the primary communication circuit  104 A and/or another of the secondary communication circuits  114 A- 114 N via wireless communication channels (not shown). In some example embodiments, resynchronization operations as performed as needed by one or more of the secondary communication circuits  114 A- 114 N. Without limitation, example resynchronization operations include identifying if a secondary wireless transceiver is in an active state or a reset state. If the secondary wireless transceiver is in the active state, resynchronization options may include using a configuration channel or data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. If the secondary wireless transceiver is in the reset state, resynchronization options may include: scanning multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronizing the secondary wireless transceiver with the established wireless network based on the identified active channel. 
       FIG.  3 A  is a diagram of a wireless management network protocol  300  in accordance with an example embodiment. The protocol  300  supports data transfers between a primary wireless transceiver (e.g., the primary wireless transceiver  106  in  FIG.  1   ) and secondary wireless transceivers (each secondary wireless transceiver  116  in  FIG.  1   ) in a system (e.g., the system  100  in  FIG.  1   , or the system  200  in  FIG.  2   ) with managed subsystems. 
     In  FIG.  3 A , time is divided into slots and the primary wireless transceiver transmits packets in the downlink (DL) slot, while the secondary wireless transceivers transmit their packets in respective uplink (UL) slots. The time interval that includes a single DL slot (for the primary wireless transceiver to transmit packets) and all UL slots (for each secondary wireless transceivers to transmit packets) is called a superframe interval. In the wireless management network protocol  300 , one superframe is represented. Over time, the wireless management network protocol  300  may use a plurality of such superframes (one superframe after another superframe, etc.) to support data transfers between: 1) a primary wireless transceiver and a secondary wireless transceiver; or 2) a secondary wireless transceiver and another secondary wireless transceiver. While  FIG.  3 A  shows data communications involving multiple secondary wireless transceivers, there are scenarios (e.g., in a scanning/joining phase) when only the primary wireless transceiver and a single secondary wireless transceiver exchange information that is needed for the secondary wireless transceiver to join a network. 
     In the wireless management network protocol  300 , resynchronization operations are performed as needed. Without limitation, example resynchronization operations include identifying if a secondary wireless transceiver is in an active state or a reset state. If the secondary communication transceiver is in the active state, resynchronization options may include using a configuration channel or data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. If the secondary wireless transceiver is in the reset state, resynchronization options may include: scanning multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronizing the secondary wireless transceiver with the established wireless network based on the identified active channel. 
     An overview of some example resynchronization options is now given. First, a secondary wireless transceiver can be in one of two states, an active state or a reset state, when synchronization is lost. Since the conditions surrounding these two states vary, they are treated as separated events with different resynchronization procedures. 
     Active device resynchronization occurs when the following conditions are met: 1) the secondary wireless transceiver is in an active state (i.e., the secondary wireless transceiver was not been reset); 2) a wireless network between the primary wireless transceiver and the secondary wireless transceiver has already been established; 3) the wireless network is assumed to still be active (i.e. the primary wireless transceiver is still transmitting to the secondary wireless transceivers); 4) the secondary wireless transceiver has maintained the frequency hopping schema of the established wireless network; and 5) the secondary wireless transceiver has lost synchronization with the primary wireless transceiver (i.e., no other errors have occurred). 
     One active wireless transceiver resynchronization option is to use configuration channels. For this option, a frequency hopping schema is selected by the primary wireless transceiver and a related frequency hopping table or other data structure is distributed to the secondary wireless transceivers during network formation. Since the configuration channels are a small subspace of the available channels, one resynchronization option inserts the configuration channels in the frequency hopping schema. For example, in the WBMS protocol, there are 40 total channels split into 37 data channels and 3 configuration channels. Therefore, after the frequency hopping table is generated by the primary wireless transceiver using only the data channels, the configuration channels are inserted at even spaces into the frequency hopping schema as shown in  FIG.  3 B . 
       FIG.  3 B  is a diagram  320  of transceiver resynchronization using configuration channels in accordance with an example embodiment. In the example of  FIG.  3 B , a configuration channel is inserted at every fifth index of the frequency hopping schema. When a secondary wireless transceiver loses synchronization, the secondary wireless transceiver will switch to the next configuration channel and wait in receive mode until the next packet is received from the primary wireless transceiver. However, if the secondary wireless transceiver loses synchronization in the last data channel before a configuration channel, the drift may cause the secondary wireless transceiver to miss the resynchronization packet. Therefore, the secondary wireless transceiver may switch to the subsequent configuration channel if needed. Using  FIG.  3 B  as an example, if a secondary wireless transceiver loses synchronization while in data channel 9, the secondary wireless transceiver will wait in configuration channel 2. However, if the secondary wireless transceiver loses synchronization in data channel 15, the secondary wireless transceiver will skip configuration channel 2 and will wait in configuration channel 1 to receive the next packet from the primary wireless transceiver. 
     In some example embodiments, the maximum resynchronization delay is given as: 
       maximum delay= t   sf ( T   CC +1),  Equation (1)
 
     where T CC  is the period of the configuration channels and t sf  is the superframe time. The maximum delay is thus proportional to the frequency of configuration channels in the frequency hopping schema. However, if the configuration channels are used by other wireless devices they could suffer from increased interference. Additionally, if the configuration channels are only used for resynchronization, inserting the configuration channels into the frequency hopping schema also creates dead time for the synchronized wireless transceivers and data transmission delays. The next resynchronization option addresses the potential limitations of using configuration channels in the frequency hopping schema for resynchronization. 
     Another active wireless transceiver resynchronization option is to use data channels of the frequency hopping schema for resynchronization. With this option, configuration channels are not needed for resynchronization. Instead, a secondary wireless transceiver maintains the time elapsed (t elapsed_since_sync ) since the last primary wireless transceiver packet was received. In some example embodiments, the value of t sync  as well as t sf  and the maximum drift (t max_drift ) are used to approximate the total drift (t total_drift ) as: 
     
       
         
           
             
               
                 
                   
                     t 
                     
                       total 
                       ⁢ 
                       _ 
                       ⁢ 
                       drift 
                     
                   
                   = 
                   
                     
                       
                         t 
                         
                           m 
                           ⁢ 
                           a 
                           ⁢ 
                           x 
                           ⁢ 
                           _ 
                           ⁢ 
                           drift 
                         
                       
                       
                         t 
                         sf 
                       
                     
                     * 
                     
                       
                         t 
                         
                           elapsed 
                           ⁢ 
                           _ 
                           ⁢ 
                           since 
                           ⁢ 
                           _ 
                           ⁢ 
                           sync 
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     In some example embodiments, t total_drift  is used to approximate the number of missed superframes (n sf ) as well as the next frequency (channel next ) that a secondary wireless transceiver should use for resynchronization. More specifically, n sf  may be calculated as: 
     
       
         
           
             
               
                 
                   
                     n 
                     sf 
                   
                   = 
                   
                     
                       
                         
                           t 
                           
                             total 
                             ⁢ 
                                 
                             drift 
                           
                         
                         + 
                         
                           t 
                           elapsedSincesync 
                         
                       
                       
                         t 
                         sf 
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     In some example embodiments, channel next  is calculated as: 
       channel next =frequency hopping table[index of (channel last )+ n   sf )].  Equation (4)
 
     Accordingly, the maximum delay is based on t total_drift  and the number of missed superframes before a secondary wireless transceiver begins resynching. For example, assuming t total_drift  is less than one superframe and two missed packets from the primary wireless transceiver triggers a secondary wireless transceiver to start resynchronization, the maximum delay would be three superframes. This second resynchronization approach decreases the amount of dead time in the frequency hopping schema and has a faster resynchronization time compared to using configuration channels for resynchronization. 
     In some example embodiments, reset wireless transceiver resynchronization is performed when the following conditions are met: 1) the secondary wireless transceiver has been reset; 2) communication between the primary wireless transceiver and the secondary wireless transceiver has already been established; 3) the established network is assumed to still be active (i.e., the primary wireless transceiver is still transmitting to the secondary wireless transceivers); and 4) the secondary wireless transceivers retained the network configuration from the last connection. 
     Using the previous network information, a reset secondary wireless transceiver can intelligently scan through multiple channels during each superframe to determine the active channel and resynchronize to the established network. The scan time is defined as the amount of time the lost secondary wireless transceiver needs to scan a channel to determine if the network is active on that channel. To determine the active channel, the following information may be stored in memory (e.g., non-volatile memory): the frequency hopping schema, t sf , and the guard time (t guard ) before the primary wireless transceiver transmits at the beginning of each superframe. In some example embodiments, t guard  along with the symbol rate (d s ), the number of preamble symbols (s p ), the number of syncword symbols (s s ), and a buffer time (t buffer ) are used to calculate the scan time (t scan ) as: 
         t   scan   =t   guard   +d   s ( s   p   +S   s )+ t   buffer .  Equation (5)
 
     In some example embodiments, a lost secondary wireless transceiver will scan through the channels using the frequency hopping schema information stored in memory. The number of channels (n channels ) that can be scanned in one superframe is based on t scan  and the size of the superframe. In some example embodiments, n channels  is calculated as: 
     
       
         
           
             
               
                 
                   
                     n 
                     channels 
                   
                   = 
                   
                     
                       
                         t 
                         sf 
                       
                       
                         t 
                         scan 
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
     The maximum number of superframes (n sf ) it takes for a reset wireless transceiver to resynchronize to the established network depends on the number of data channels (n data ) that can be scanned during each superframe. In some example embodiments, n sf  is calculated as: 
     
       
         
           
             
               
                 
                   
                     n 
                     sf 
                   
                   = 
                   
                     
                       
                         n 
                         data 
                       
                       
                         n 
                         channels 
                       
                     
                     + 
                     1. 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                       
                   
                     ( 
                     7 
                     ) 
                   
                 
               
             
           
         
       
     
     For example, if 10 channels can be scanned in one superframe and there are 20 data channels, then the reset secondary wireless transceiver will resynchronize to the established network within three superframes. This approach allows a reset secondary wireless transceiver to resynchronize with an established network in a decreased number of superframes and this enables the network to continue operating while complying with the target time interval. 
       FIG.  4    is a diagram of a WBMS  400  in accordance with an example embodiment. As shown, the WBMS  400  includes battery cells  402 A- 402 H (e.g., Li-ion cells) in series. Each of the battery cells  402 A- 402 H is coupled to a respective module  404 A- 404 H (examples of the modules  230 A- 230 N in  FIG.  2   ) to form respective subsystems (e.g., the battery cell  402 A and the module  404 A is an example of a subsystem as described herein). The modules  404 A- 404 H may perform monitoring, adjustment, data transfers, and/or resynchronization operations as described herein. 
     In the example of  FIG.  4   , the WBMS  400  includes control circuitry  204 A (an example of the control circuitry  204  in  FIG.  2   ) with a microcontroller  102 B (an example of the controller  102  in  FIG.  1   , or the microcontroller  102 A in  FIG.  2   ), a primary communication circuit  104 B (an example of the primary communication circuit  104  in  FIG.  1   , or the primary communication circuit  104 A in  FIG.  2   ), and a communication interface  130 B (an example of the communication interface  130  in  FIG.  1   , or the communication interface  130 A in  FIG.  2   ). In the example of  FIG.  4   , the microcontroller  102 B and the primary communication circuit  104 B communicate via a wired transceiver protocol such as a Universal Asynchronous Receiver-Transmitter (UART) protocol, a serial peripheral interface (SPI) protocol, or other wired transceiver protocol. Also, the communication interface  130 B may be a vehicle communication interface such as a controller area network (CAN) interface, an Ethernet interface, or other communication interface. As shown, the control circuitry  204 A is coupled to an antenna  408  for wireless communications with the modules  404 A- 404 H. In operation, the primary communication circuit  104 B is configured to perform wireless data transfers and resynchronization operations as described herein. 
     With the WBMS  400 , the functionality of the battery cells  402 A- 402 H is combined and the combined functionality of all of the battery cells  402 A- 402 H is monitored and adjusted as needed. For example, the performance of the battery cells  402 A- 402 H may degrade over time. In such case, adjustment or replacement of a specific one of the battery cells  402 A- 402 H or other components of the modules  404 A- 404 H may be needed. By using the primary communication circuit  104 B and the secondary communication circuits  414 A- 414 H for wireless data transfers between the microcontroller  102 B and modules  404 A- 404 H such replacement is facilitated while supporting monitoring, adjustment, status update, parameter transfer, and/or other operations related to the battery cells  402 A- 402 H. The use of resynchronization operations with the WBMS  400  ensures wireless communications for battery management system operations comply with a target time interval (e.g., a safety standard). Without limitation, example resynchronization operations include identifying if a secondary wireless transceiver is in an active state or a reset state. If the secondary communication transceiver is in the active state, resynchronization options may include using a configuration channel or data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. If the secondary wireless transceiver is in the reset state, resynchronization options may include: scanning multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronizing the secondary wireless transceiver with the established wireless network based on the identified active channel. 
       FIG.  5    is a block diagram of a BMU  502  and a CMU  522  in accordance with an example embodiment. In some example embodiments, the BMU  502  and the MCU  522  are part of a BMS, such as a WBMS, for a system (e.g., the system  100  in  FIG.  1   , the system  200  in  FIG.  2   , or the WBMS  400  in  FIG.  4   ). The MCU  502  may include, for example, a PCB or other unit with a safety microcontroller  504  (an example of the controller  102  in  FIG.  1   , the microcontroller  102 A in  FIG.  2   , of the microcontroller  102 B in  FIG.  4   ) and a communication circuit  506  (e.g., the primary communication circuit  104  in  FIG.  1   , the primary communication circuit  104 A in  FIG.  2   , or the primary communication circuit  104 B in  FIG.  4   ) coupled to each other via a wired coupling  105 A (an example of the wired coupling  105  in  FIG.  1   ). The microcontroller  504  is also coupled to a vehicle network via communication interface  540  (an example of the communication interface  130  in  FIG.  1   , the communication interface  130 A in  FIG.  2   , or the communication interface  130 B in  FIG.  4   ). 
     In the example of  FIG.  5   , the communication circuit  506  includes resynchronization circuitry  111 A (an example of the resynchronization circuitry  111  in  FIG.  1   ). The communication circuit  506  may additionally include other components such as those described for the primary communication circuit  104  in  FIG.  1   . In some example embodiments, the communication circuit  506  is configured to perform the operations described for the primary communication circuit  104  in  FIG.  1   , the primary communication circuit  104 A in  FIG.  2   , or the primary communication circuit  104 B in  FIG.  4   . 
     The CMU  522  may include, for example, a PCB or other unit with a monitor circuit  538  (an example of the monitor circuit  122  in  FIG.  1   , or one of the monitor circuits  122 A- 122 N in  FIG.  2   ) and a communication circuit  526  (e.g., the secondary communication circuit  114  in  FIG.  1   , one of the secondary communication circuits  114 A- 114 N in  FIG.  2   , or one of the secondary communication circuits  114 A- 114 H in  FIG.  4   ) coupled to each other via a wired coupling  115 A (an example of the wired coupling  115  in  FIG.  5   ). 
     In the example of  FIG.  5   , the communication circuit  526  includes resynchronization circuitry  121 A (an example of the resynchronization circuitry  121  in  FIG.  1   ). The communication circuit  526  may additionally include other components such as those described for the secondary communication circuit  114  in  FIG.  1   . In some example embodiments, the communication circuit  526  is configured to perform the operations of the secondary communication circuit  114  in  FIG.  1   , one of the secondary communication circuits  114 A- 114 N in  FIG.  2   , or one of the secondary communication circuit  114 A- 114 H in  FIG.  4   . 
     In the example of  FIG.  5   , the wireless connection between the communication circuits  506  and  526  is referred to as a black channel  516  because the wireless connection does not comply with standards of the safety microcontroller  504  and the monitor circuit  538 . In order to ensure communications between the safety microcontroller  504  and the monitor circuit  538  comply with a communications latency standard, the communication circuit  506  includes the resynchronization circuitry  111 A and the communication circuit  526  includes the resynchronization circuitry  121 A. Without limitation, example resynchronization operations include identifying if a secondary communication transceiver is in an active state or a reset state. If the secondary communication transceiver is in the active state, resynchronization options may include using a configuration channel or data channel within a frequency hopping schema of the established wireless network to resynchronize the secondary wireless transceiver with the established wireless network. If the secondary wireless transceiver is in the reset state, resynchronization options may include: scanning multiple channels within a frequency hopping schema of the established wireless network to identify an active channel; and resynchronizing the secondary wireless transceiver with the established wireless network based on the identified active channel. 
     As another option, a secondary wireless transceiver in an active state may initiate resynchronization in response to missing a predefined number of primary wireless transceiver downlinks. As another option, a secondary wireless transceiver in a reset state may detect a start-up sequence after reset based on a valid non-volatile memory space. If the reset was manually triggered, a flag could be used to initiate resynchronization. As another option, if the reset was not manually triggered, the secondary wireless transceiver may scan the configuration channels within the frequency hopping schema of the established wireless network to detect if an active network formation sequence is ongoing. If not, the secondary wireless transceiver can switch to resynchronization using the data channels (e.g., based on received signal strength indication or “RSSI” sensing). If the secondary wireless transceiver then detects the correct channel and the primary wireless transceiver ID does not match, the second wireless transceiver may perform normal pairing operations. 
     In some example embodiments, a secondary wireless transceiver detects its reset state based on a valid non-volatile memory space. In a scenario where the non-volatile memory space of the secondary wireless transceiver is not valid, the primary wireless transceiver may eventually restart the network (e.g., after a prolonged duration, after an expected maximum time allowed for a secondary wireless transceiver to resynchronize, and/or after a command from the safety microcontroller). 
       FIG.  6    is a diagram of a communication circuit  600  (an example of the primary communication circuit  104  in  FIG.  1   , the primary communication circuit  104 A in  FIG.  2   , the primary communication circuit  104 B in  FIG.  4   , the communication circuit  506  in  FIG.  5   , the secondary communication circuit  114  in  FIG.  1   , one of the secondary communication circuits  114 A- 114 N in  FIG.  2   , one of the secondary communication circuits  114 A- 114 H in  FIG.  4   , or the communication circuit  526  in  FIG.  5   ) in accordance with an example embodiment. As shown, the communication circuit  600  includes a main central processing unit (CPU)  602 , a Joint Test Action Group (JTAG) interface  604 , read-only memory (ROM)  606 , Flash memory  608 , and static random-access memory (SRAM)  610 . 
     The communication circuit  600  also includes a radio frequency (RF) core  612  (e.g., to provide the primary wireless transceiver  106  or the secondary wireless transceiver  116  in  FIG.  1   ). In the example of  FIG.  6   , the RF core  612  includes a transit chain  614  and a receive chain  616  coupled to antenna terminals  615  and  617 . The receive chain  616  is coupled to a sampler  618 , which outputs samples of received data to analog-to-digital converters (ADCs)  620  and  622 . The digitized samples are provided to a digital signal processor (DSP) modem  626 . As shown, the transmit chain  614  and the sampler  618  are also coupled to a digital phase-locked loop (PLL)  624  to manage timing of receive operations and/or transmit operations. Other example components of the RF core  612  include a processor  628 , SRAM  630 , and ROM  632 . 
     As shown, the communication circuit  600  also includes hardware peripherals and modules  640 . Without limitation, examples of the hardware peripherals and modules  640  include: serial communications interfaces (e.g., I 2 C, I 2 S, SPI, etc.); one or more UARTs, a direct memory access (DMA) interface; general programmable input/outputs (GPIOs); an encryption module (e.g., AES-256); a hashing module (e.g., SHA2-512); timers; an error correction code (ECC) module; a cryptosystem module (e.g., RSA); a watchdog timer; and a real-time clock (RTC) module. 
     In the example of  FIG.  6   , the communication circuit  600  further includes circuitry  650  such as a low-dropout regulator (LDO), clocks, references, and a direct-current to direct-current (DC/DC) converter. In some example embodiments, the communication circuit  600  also includes a sensor interface  660  with various components to support sensor operations. Without limitation, example components of the sensor interface  660  include: a sensor controller; a digital-to-analog converter (DAC), an ADC, a comparator, a digital sensor interface (IF), a capacitive touch IF, a time-to-digital converter, and SRAM. With the communication circuit  600 , a wired transceiver (e.g., the UART or SPI modules of the hardware peripherals and modules  640 ) and a wireless transceiver (e.g., the RF core  612 ) are configured to perform network formation, data transfer, and resynchronization as described herein. 
     In some example embodiments, a secondary wireless transceiver (e.g., the secondary wireless transceiver  116  in  FIG.  1   , or related components of the communication circuit  600  in  FIG.  6   ) is configured to: identify a resynchronization trigger; and perform resynchronization with the established wireless network in response to the identified resynchronization trigger within a target time interval. In some example embodiments, if the secondary wireless transceiver is in as an active state, the secondary wireless transceiver is configured to use a configuration channel within a frequency hopping schema of the established wireless network to resynchronize with the established wireless network. In such embodiments, the secondary wireless transceiver is configured to: switch to a next available configuration channel within the frequency hopping schema in response to losing synchronization with the established wireless network; and wait in a receive mode at the next available configuration channel until a next packet is received from the primary wireless transceiver. 
     In some example embodiments, if the secondary wireless transceiver is in as an active state, the secondary wireless transceiver is configured to use a data channel within a frequency hopping schema of the established wireless network to resynchronize with the established wireless network. In such example embodiments, the secondary wireless transceiver is configured to: estimate a number of missed superframes of the established wireless network in response to losing synchronization with the established wireless network; and use the estimated number of missed superframes to resynchronize the secondary wireless transceiver with the established wireless network. 
     In some example embodiments, if the secondary wireless transceiver is in a reset state, the secondary wireless transceiver is configured to: scan multiple channels within a frequency hopping schema to identify an active channel; and resynchronize with the established wireless network based on the identified active channel. In such example embodiments, the secondary wireless transceiver is configured to scan all channels within the frequency hopping schema within the target time interval. 
       FIG.  7    is a flowchart of a communication circuit method  700  in accordance with an example embodiment. The method  700  is performed, for example, by a communication circuit (e.g., the primary communication circuit  104  in  FIG.  1   , the primary communication circuit  104 A in  FIG.  2   , the primary communication circuit  104 B in  FIG.  4   , the communication circuit  506  in  FIG.  5   , the secondary communication circuit  114  in  FIG.  1   , one of the secondary communication circuits  114 A- 114 N in  FIG.  2   , one of the secondary communication circuits  114 A- 114 H in  FIG.  4   , or the communication circuit  526  in  FIG.  5   ) between a controller and a subsystem (see e.g.,  FIG.  1   ). As shown, the method  700  includes establishing a wireless network with another communication circuit to transfer data between the controller and the subsystem at block  702 . At block  704 , a resynchronization trigger is identified. At block  706 , resynchronization with the established wireless network is performed within a target time interval in response to the identified resynchronization trigger. 
     In some example embodiments, performing resynchronization at block  706  includes: identifying an active wireless transceiver state; and in response to identifying the active wireless transceiver state, using a configuration channel within a frequency hopping schema of the established wireless network to resynchronize with the established wireless network. In such example embodiments, performing resynchronization may include switching to a next available configuration channel within the frequency hopping schema in response to losing synchronization with the established wireless network; and waiting in a receive mode at the next available configuration channel until a next packet is received from the primary wireless transceiver. 
     In some example embodiments, performing resynchronization at block  706  includes: identifying an active wireless transceiver state; and in response to identifying the active wireless transceiver state, using a data channel within a frequency hopping schema of the established wireless network to resynchronize with the established wireless network. In such example embodiments, performing resynchronization includes: estimating a number of missed superframes of the established wireless network in response to losing synchronization with the established wireless network; and using the estimated number of missed superframes to resynchronize the secondary wireless transceiver with the established wireless network. 
     In some example embodiments, performing resynchronization at block  706  includes: identifying a reset wireless transceiver state; in response to identifying the reset wireless transceiver state, scanning multiple channels within a frequency hopping schema to identify an active channel; and resynchronizing with the established wireless network based on the identified active channel. In such example embodiments, the secondary wireless transceiver is configured to scan all channels within the frequency hopping schema within the target time interval. 
     In this description, the term “couple” may cover connections, communications, or signal paths that enable a functional relationship consistent with this description. For example, if device A generates a signal to control device B to perform an action: (a) in a first example, device A is coupled to device B by direct connection; or (b) in a second example, device A is coupled to device B through intervening component C if intervening component C does not alter the functional relationship between device A and device B, such that device B is controlled by device A via the control signal generated by device A. 
     A device that is “configured to” perform a task or function may be configured (e.g., programmed and/or hardwired) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or re-configurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construc-tion and/or layout of hardware components and interconnections of the device, or a combination thereof. 
     A circuit or device that is described herein as including certain components may instead be adapted to be coupled to those components to form the described circuitry or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and/or inductors), and/or one or more sources (such as voltage and/or current sources) may instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and/or IC package) and may be adapted to be coupled to at least some of the passive elements and/or the sources to form the described structure either at a time of manufacture or after a time of manufacture, for example, by an end-user and/or a third-party. 
     Circuits described herein are reconfigurable to include additional or different components to provide functionality at least partially similar to functionality available prior to the component replacement. Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in series and/or parallel to provide an amount of impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two nodes as the single resistor or capacitor. 
     Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.