JP6379925B2 - Communication waveform generator - Google Patents

Description

  The present invention relates to a communication waveform generation device applied to each of a plurality of nodes constituting a communication system using a first PWM signal and a second PWM signal having a duty ratio smaller than that of the first PWM signal.

  As a communication system mounted on a vehicle, one using a communication bus such as a CAN (Controller Area Network) or a LIN (Local Interconnect Network) is known. Some types of communication systems include a master node that outputs a synchronization signal including a clock component to a communication bus, and a slave node that operates by receiving the synchronization signal via the communication bus.

  In such a communication system, a plurality of PWM (Pulse width modulation) signals having different duty ratios are generally used. In a communication system using a plurality of PWM signals having different logical values, in order to perform highly accurate communication, it is necessary to appropriately sample each PWM signal. Therefore, in order to prevent erroneous sampling due to noise or the like, the PWM signals are set so that their duty ratios are greatly different from each other. That is, the PWM signals are set so that their Low output widths are greatly different from each other, so that they can be easily identified.

JP 2008-192324 A

  However, the internal resistance value of each node varies due to a manufacturing error or the like. For this reason, for example, the time until the slave node receives the PWM signal from the master node via the communication bus and the slave node outputs the PWM signal, the accuracy, etc. may vary from individual to individual.

  Due to the influence of such variations, the Low output width of the PWM signal transmitted through the communication bus deviates from an appropriate one. For this reason, the PWM signals having different logical values output from the respective nodes should have a difference in the Low output width, but the difference may be reduced due to such divergence. As a result, erroneous sampling of the PWM signal is likely to occur.

  The present invention has been made in view of such a problem, and an object thereof is a communication waveform capable of improving the sampling accuracy of the first PWM signal and the second PWM signal which are different from each other in duty ratio and output to the communication bus. It is to provide a generation device.

In order to solve the above problems, a communication waveform generation device according to the present invention includes a plurality of nodes (10) constituting a communication system (CS) using a first PWM signal and a second PWM signal having a duty ratio smaller than that of the first PWM signal. , 100 to n) is a communication waveform generation device (30, 130) applied to each, and an output means (31, 130) for outputting the first PWM signal or the second PWM signal to the communication bus (BS) of the communication system. 131), receiving means (35, 135) for receiving the first PWM signal or the second PWM signal output to the communication bus, and correcting the first PWM signal or the second PWM signal output by the output means. Correction means (35, 135), wherein the correction means outputs the first PWM signal output from the output means and received by the reception means. Alternatively, the first PWM signal or the second PWM signal output by the output unit based on a difference (LW2) between a Low output width (LW) of the second PWM signal and a predetermined Low output reference width (LW1) a shall be corrected for Low output width. The output unit superimposes a predetermined Low output width on the first PWM signal received by the receiving unit and outputs the first PWM signal as a second PWM signal to the communication bus. The receiving means receives the second PWM signal output in this way. The correction means performs self-other discrimination that specifies whether or not the second PWM signal is output from another communication waveform generation device, and is output from another communication waveform generation device as a result of the self-other determination. If not, the Low output width of the second PWM signal is corrected.

  In the present invention, the first PWM signal or the second PWM signal output to the communication bus based on the difference between the Low output width of the first PWM signal or the second PWM signal received from the communication bus and a predetermined Low output reference width. The Low output width is corrected. Therefore, based on the state of the first PWM signal or the second PWM signal transmitted through the communication bus while being influenced by various error factors, the Low output width of the first PWM signal or the second PWM signal output to the communication bus is output as Low. It is possible to perform correction so as to approach the reference width. Thus, the first PWM signal and the second PWM signal can be clearly different from each other, and the sampling accuracy can be improved.

  According to the present invention, it is possible to provide a communication waveform generation device capable of improving the sampling accuracy of the first PWM signal and the second PWM signal that are different from each other in duty ratio and output to the communication bus.

It is a block diagram which shows the structure of the communication system with which the communication waveform generation apparatus which concerns on embodiment of this invention was applied. It is explanatory drawing which shows the structure of the signal corresponded to the logical values 1 and 0 transmitted with a communication bus. It is a timing diagram which shows the output and reception of the PWM signal by the communication system which concerns on a comparative example. It is a timing diagram which shows the output and reception of the signal by the communication system with which the communication waveform generation apparatus which concerns on embodiment of this invention was applied. It is explanatory drawing explaining the self-others determination of a signal. It is explanatory drawing explaining the self-others determination of the signal which concerns on the 1st modification of embodiment of this invention. It is explanatory drawing explaining the self-others determination of the signal which concerns on the 2nd modification of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  First, the configuration of a communication system CS to which a communication waveform generation device according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 and 2. The communication system CS is an in-vehicle communication system to which a master-slave communication protocol is applied. In addition, the communication system CS includes a master node 10 connected via a communication bus BS and a plurality of slave nodes 100 to n. Hereinafter, the master node 10 is simply referred to as the master 10, and the slave nodes 100 and 200 to n are simply referred to as the slaves 100 to n.

  Here, the hardware configurations of the slaves 100 to n are the same as the hardware configuration of the master 10. Therefore, the configuration of the master 10 will be mainly described below, and the description of the configurations of the slaves 100 to n will be omitted as appropriate. In FIG. 1, the components of the master 10 are given a two-digit code such as “controller 20”, and the components of the slave 100 are given a code in the 100s such as “controller 120”. The reference numerals of the components corresponding to each other share the last two digits. Further, illustration of the configuration of slave nodes other than the slave 100 is omitted.

  The master 10 is an electronic control unit (ECU) that acquires the state of the vehicle detected by various devices mounted on the vehicle and outputs a PWM signal to the device to control the vehicle. There is only one in the CS. The master 10 has a controller 20 and a transceiver IC 30.

  The controller 20 is a well-known microcomputer including a CPU, a ROM, a RAM, an IO port, and the like. The controller 20 transmits and receives data TX and RX.

  The transceiver IC 30 includes a PWM processing unit 31, an analog circuit 33, an update processing unit 35, and a memory 36. FIG. 1 illustrates each function of the transceiver IC 30 as a block.

  The PWM processing unit 31 performs PWM encoding on the data TX input from the controller 20 based on a target width stored in a memory 36 described later, and generates a PWM signal. The PWM processing unit 31 outputs this PWM signal to the analog circuit 33.

  The analog circuit 33 is a delay circuit that delays the PWM signal output from the PWM processing unit 31 to the communication bus BS.

  In addition to receiving signals from the communication bus BS, the update processing unit 35 monitors the operation of the PWM processing unit 31 and instructs the PWM processing unit 31 of the low output width of the PWM signal output from the PWM output unit 31. Further, the update processing unit 35 appropriately updates a target width stored in a memory 36 described later.

  Various information is stored in the memory 36, and one of the information is a “target width” that is a target value of the Low output width of the PWM signal output from the PWM processing unit 31. This target width is appropriately updated by the update processing unit 35. The PWM processing unit 31 reads the target width stored in the memory 36 and performs PWM encoding based on the target width.

  In the communication system CS configured as described above, a signal transmitted through the communication bus BS is a PWM signal whose signal level changes from a low level to a high level in the middle of a bit, as shown in FIG.

  Each of the dominant signal (corresponding to the logical value 1 in the present embodiment) and the recessive signal (corresponding to the logical value 0 in the present embodiment) of the communication system CS is expressed by two types of duty ratios. Specifically, the master 10 outputs a first PWM signal and a second PWM signal to the communication bus BS, and at least one of the slaves 100 to n is a first PWM with a relatively large duty ratio output from the master 10 to the communication bus BS. A second PWM signal (Low) having a relatively small duty ratio is obtained by superimposing a predetermined Low output width on at least one of the slaves 100 to n on a signal (a signal with a relatively low output width, corresponding to a logical value 1). A signal having a relatively large output width (corresponding to a logical value 0) is generated. In each of the first PWM signal and the second PWM signal, a falling occurs at the head of the bit. Since the first PWM signal and the second PWM signal transmitted through the communication bus BS are affected by the resistance of the communication bus BS, as shown in FIG. 2, the falling and rising thereof are slightly inclined.

  The communication system CS is set so that when the first PWM signal and the second PWM signal collide with each other on the communication bus BS, the second PWM signal that is the dominant signal wins arbitration. As a result, of the master 10 or the slaves 100 to n, the node that has lost the arbitration immediately stops outputting the signal, and only the node that has won the arbitration can continue the output.

  Next, communication by the communication system according to the comparative example and its problems will be described with reference to FIG. Similar to the communication system CS according to the embodiment of the present invention, the communication system according to this comparative example is a communication system to which a well-known master-slave communication protocol is applied, and has a superiority signal (corresponding to logical value 0) and inferiority. Each of the signals (corresponding to logical value 1) is expressed by two types of duty ratios. However, the communication system according to this comparative example differs from the communication system CS in that the Low output width of the output signal is not updated.

  In both the communication system CS and the communication system according to the comparative example, individual differences may occur in the characteristics of the master node and each slave node due to a manufacturing error or the like. That is, the resistance value and the like in the transceiver IC vary for each node, and the influence based on this also affects communication.

  For example, when the slave node A generates a second PWM signal by superimposing a predetermined low output width on the first PWM signal output from the master node, delays d1 to d5 may occur. Hereinafter, the delays d1 to d5 will be described.

  First, a delay d1 until the first PWM signal output from the master node to the communication bus is received by the slave node A may occur. That is, a delay d1 occurs due to a factor such as a comparator until the signal level of the first PWM signal transmitted from the master node transmitted through the communication bus falls below a predetermined threshold value X and is received at the slave node A. sell.

  Further, there may be a delay d2 until the transceiver IC of the slave node A detects the first PWM signal output from the master node to the communication bus and outputs the second PWM signal. This is due to variations in the clock frequency of the transceiver IC.

  Due to variations in the transmission accuracy of the transceiver IC of the slave node A, a delay d3 can also occur in the Low output width of the slave node A. The delay d4 can also occur when the signal passes through the analog circuit of the transceiver IC of the slave node A. Further, due to variations in the performance of the analog circuit of the transceiver IC, a delay d5 may also occur in the delay amount provided by the analog circuit.

  On the other hand, in the case of the slave node B where the delays d1 to d5 are very small, the Low PWM output width of the second PWM signal output from the slave node B to the communication bus is much smaller than that of the slave node A. In this case, the duty ratio of the second PWM signal becomes large, and the difference in Low output width between the first PWM signal and the second PWM signal becomes very small.

  As described above, since the difference in the Low output width between the first PWM signal and the second PWM signal becomes small, erroneous sampling may occur in other nodes. For this reason, the communication accuracy of a communication system falls and there exists a possibility that exact control may not be performed.

  For such a problem, in the communication system CS according to the embodiment of the present invention, each node updates the target width stored in the memory, and the Low output of the first PWM signal or the second PWM signal output from each node. By correcting the width, erroneous sampling is prevented. Hereinafter, correction of the Low output width of the PWM signal by the communication system CS will be described with reference to FIGS. 4 and 5. Here, a case will be described in which the slave 100 generates a second PWM signal by superimposing a predetermined Low output width on the first PWM signal output from the master 10.

  First, when the transceiver IC 130 of the slave 100 receives the first PWM signal output from the master 10 to the communication bus BS and transmitted through the communication bus BS, the PWM processing unit 131 sets the target width stored in the memory 36. Based on the PWM encoding. The PWM processing unit 131 outputs the second PWM signal to the communication bus BS via the analog circuit 33.

  Next, the update processing unit 135 of the transceiver IC 130 of the slave 100 receives from the communication bus BS the second PWM signal that is output to the communication bus BS and transmitted through the communication bus BS. Further, the update processing unit 135 of the transceiver IC 130 calculates a low output width LW of the second PWM signal received from the communication bus BS and a low output reference width LW1 that is a predetermined low output width corresponding to the logical value 0. The difference LW2 is calculated.

  When the difference LW2 is obtained as a result of the calculation, the update processing unit 135 sets the target width stored in the memory 36 so that the Low output width of the second PWM signal transmitted through the communication bus BS is increased by the difference LW2. Update.

  After updating by the update processing unit 135, the transceiver IC 130 of the slave 100 performs PWM encoding based on the updated target width stored in the memory 36. As a result, the Low output width of the second PWM signal output from the slave 100 to the communication bus BS and transmitted through the communication bus BS is corrected. Thereby, the second PWM signal corresponding to the logical value 0 is clearly different from the first PWM signal corresponding to the logical value 1.

  Here, the signal received by the transceiver IC 130 from the communication bus BS for the correction of the Low output width must be transmitted and transmitted from the transceiver IC 130 itself to the communication bus BS. That is, it is necessary for the transceiver IC 130 to execute a self-other determination to determine whether the signal received from the communication bus BS is output from the transceiver IC 130 itself or from the transceiver IC of another node. is there.

  Therefore, the transceiver IC 130 performs the self-other determination based on the communication protocol of the communication system CS. In the communication protocol, as shown in FIG. 5, when the master 10 outputs a signal for requesting the output of the second PWM signal to any of the slaves 100 to n, the slaves 100 to n are specified in the output signal. ID information is set to be included. Any one of the slaves 100 to n identified by the ID information is configured to output the second PWM signal as a response thereto.

  This operation will be described taking the slave 100 as an example. The slave 100 determines whether or not the ID information included in the output signal received by the transceiver IC 130 after the period indicating no signal corresponds to itself. And when the said ID information corresponds to self, it judges that the 2nd PWM signal received after that was output by self. Only in that case, the slave 100 updates the target width stored in the memory 36 and corrects the Low output width. As a result, the target width is not updated based on a signal that another slave or the master 10 outputs to the communication bus BS by mistake.

  As described above, the slave 100 of the communication system CS sets the Low output width of the second PWM signal output by the slave 100 based on the state of the second PWM signal transmitted through the communication bus BS while being affected by various error factors. Correction can be made so as to approach the Low output reference width LW1. Thereby, the first PWM signal and the second PWM signal can be clearly different from each other, and the sampling accuracy can be improved.

  Next, a first modification of the embodiment of the present invention will be described with reference to FIG. In the first modified example, the self-other determination method for determining whether the signal received from the communication bus BS by each node is output by the node itself or output by another node, This is different from the previous embodiment.

  In the first modification, a period during which each node outputs a signal is determined in advance, and the self-other determination is executed based on the period. That is, using the start signal output to the communication bus BS when the vehicle is started as a trigger, the master 10 and the slaves 100 to n and the period for which the signal output is sequentially permitted are respectively set. Updating of the target width is permitted during the period when the output is permitted. Therefore, the transceiver IC of the master 10 and the slaves 100 to n does not update the target width stored in the memory based on the signal that the other slave or the master 10 outputs to the communication bus BS by mistake. . Further, by performing such processing at the time of starting the vehicle, it becomes possible to perform the update without affecting the traveling of the vehicle.

  Next, a second modification of the embodiment of the present invention will be described with reference to FIG. Also in this second modified example, a method of self-other judgment for judging whether a signal received from a communication bus BS by each node is a signal output by the node itself or a signal output by another node, This is different from the previous embodiment.

  In the second modification, each of the master 10 and the slaves 100 to n outputs an identification signal indicating that it outputs before the signal is output to the communication bus BS. The master 10 may output this identification signal when the master 10 transmits an output signal to the slaves 100 to n. When the identification signal is transmitted through the communication bus BS, the master 10 and the slaves 100 to n receive either one of the identification signals and the master and the slaves 100 to n identified by the identification signal within a predetermined period. It is determined that the signal has been output, and self-other determination is executed. In the second modified example, the self-other determination is executed based on the identification signal flowing in the communication bus BS in this way. Therefore, the transceiver IC of the master 10 and the slaves 100 to n does not update the target width stored in the memory based on the signal that the other slave or the master 10 outputs to the communication bus BS by mistake. .

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

BS: Communication bus CS: Communication system 10: Master node (node)
30, 130: transceiver IC (communication waveform generation means)
31, 131: PWM processing section (output means)
35, 135: Update processing unit (reception means, correction means)
100, 200, n: slave node (node)

Claims (4)

Communication waveform generator (30, 130) applied to each of a plurality of nodes (10, 100 to n) constituting a communication system (CS) using a first PWM signal and a second PWM signal having a duty ratio smaller than that of the first PWM signal. ) And
Output means (31, 131) for outputting the first PWM signal or the second PWM signal to a communication bus (BS) of the communication system;
Receiving means (35, 135) for receiving the first PWM signal or the second PWM signal output to the communication bus;
Correction means (35, 135) for correcting the first PWM signal or the second PWM signal output by the output means,
The correcting means outputs a difference between a Low output width (LW) of the first PWM signal or the second PWM signal output from the output means and received by the receiving means, and a predetermined Low output reference width (LW1) ( LW2), the Low output width of the first PWM signal or the second PWM signal output from the output means is corrected ,
The output means superimposes a predetermined Low output width on the first PWM signal received by the receiving means and outputs the second PWM signal to the communication bus,
The receiving means receives the second PWM signal output in this way,
The correction means executes self-other discrimination for specifying whether or not the second PWM signal is output by another communication waveform generation device, and outputs the other communication waveform generation device as a result of the self-other discrimination. If not , the communication waveform generation apparatus corrects the Low output width of the second PWM signal . The communication waveform generation apparatus according to claim 1 , wherein the correction unit performs the self-other determination based on a communication protocol of the communication system. At least two or more nodes constituting the plurality of nodes are configured to output the second PWM signal to the communication bus during a predetermined period,
The communication waveform generation apparatus according to claim 1 , wherein the correction unit performs the self-other discrimination in a period during which the output is permitted. At least two or more nodes constituting the plurality of nodes are configured to output identification signals that identify themselves prior to the output of the second PWM signal to the communication bus,
2. The communication waveform generating apparatus according to claim 1 , wherein the correction unit performs the self-other discrimination when the receiving unit receives the second PWM signal after receiving the identification signal that identifies the self. .

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