JP7331756B2 - Communication device - Google Patents

Description

The present disclosure relates to communication devices.

A CAN communication system is known as a communication system mounted on a vehicle. CAN is an abbreviation for "Controller Area Network". CAN is a registered trademark. The communication speed of CAN is 1 Mbps at maximum, and it is becoming difficult to cope with the increase in the amount of data communication in vehicles. Therefore, the adoption of CAN FD, which enables higher-speed communication than CAN, is progressing. CAN FD is an abbreviation for "CAN with Flexible Data-Rate".

Patent Literature 1 describes a communication device that communicates according to CAN FD.

Japanese Patent Publication No. 2015-536067

However, as a result of detailed studies by the inventors, the following problems were found. That is, in serial communication methods such as CAN and CAN FD, fluctuations in bit length due to external noise can be mentioned as a factor that hinders the increase in communication speed. The bit length referred to here is the pulse width per bit.

In the serial communication system, as the communication speed increases, the bit length of the transmission signal on the transmission path decreases. On the other hand, the amount of change in bit length due to external noise is generally constant regardless of the communication speed. For this reason, when the communication speed is increased, the ratio of the amount of variation in bit length due to external noise increases, making it impossible to transmit and receive signals normally.

One aspect of the present disclosure provides a communication device capable of suppressing the amount of variation in bit length due to external noise.

One aspect of the present disclosure is a communication device comprising a drive unit (11, 12). The driving unit receives a transmission signal that changes between high level and low level from the controller (5), and in response to the transmission signal, changes the potential of the transmission signal in the transmission line (3) to a first potential corresponding to the high level. level and a second level corresponding to the low level. The drive section includes a measurement section (11) and an adjustment section (23). The measurement unit measures the transmission signal during a change period that is at least one of a period during which the potential of the transmission signal in the transmission line changes from the first level to the second level and a period during which the potential of the transmission signal changes from the second level to the first level. It is configured to measure the slope of the potential change of the signal. When the adjustment unit determines that the measured slope, which is the slope of the potential change of the transmission signal measured by the measurement unit, is gentler than the target slope, the adjustment unit adjusts the transmission signal in the adjustment period after the measurement period in the change period. A process of adjusting the slope of the potential change to make the slope steeper, and when it is determined that the measured slope is steeper than the target slope, the slope of the potential change of the transmission signal during the adjustment period is adjusted to the slope. and adjusting to the side where the is moderate.

According to such a configuration, it is possible to suppress the amount of variation in bit length due to external noise.

2 is a block diagram showing the configuration of a communication device; FIG. FIG. 4 is an explanatory diagram for explaining the influence of external noise; 4 is a block diagram showing the configuration of a measuring section; FIG. FIG. 4 is an explanatory diagram for explaining input/output of a comparison unit; 4 is a block diagram showing the configuration of an adjustment unit; FIG. 4 is a flowchart of adjustment processing; FIG. 10 is an explanatory diagram for explaining input/output of the adjustment unit when the potential of the transmission signal changes from recessive to dominant; FIG. 10 is an explanatory diagram of adjustment processing when adjustment is made to make the inclination gentler; FIG. 10 is an explanatory diagram of adjustment processing when adjustment is made to make the inclination steeper; 4 is a timing chart for explaining adjustment processing;

Exemplary embodiments of the present disclosure are described below with reference to the drawings.
[1. composition]
The ECU 1 of the embodiment shown in FIG. 1 is an ECU as a node in a communication system mounted on a vehicle. The ECU 1 and one or more other ECUs (not shown) are connected to a transmission line 3 as a communication bus in a communication system and communicate via this transmission line 3 . ECU is an abbreviation of "Electronic Control Unit". Other ECUs also have the same configuration as the ECU 1 .

The communication protocol of the communication system is CAN FD, for example. Therefore, the transmission line 3 is a differential transmission line having a high-potential signal line 3a and a low-potential signal line 3b, and is a so-called CAN bus. Hereinafter, the potential of the high-potential signal line 3a is called CANH, and the potential of the low-potential signal line 3b is called CANL. Note that the potential is a potential based on the potential of the ground in the ECU 1 (that is, the ground potential). Each voltage value to be described later is also a potential value based on the ground potential.

When a dominant signal is output to the transmission line 3 as a transmission signal, CANH becomes a predetermined high potential for transmission (hereinafter referred to as VH), and CANL becomes a predetermined low potential for transmission (hereinafter referred to as VL) lower than VH. Become. VH is, for example, 3.5V and VL is, for example, 1.5V. Therefore, the differential voltage Vdif, which is the difference between CANH and CANL, is "VH-VL", which is 2V, for example. Further, when a recessive signal is output to the transmission line 3 as a transmission signal, both CANH and CANL are at a predetermined intermediate potential (hereinafter referred to as VM) lower than VH and higher than VL. The dynamic voltage Vdif becomes 0V. VM is, for example, 2.5V. Dominant means a dominant signal on the transmission path 3 and recessive means a inferior signal on the transmission path 3 .

The differential voltage Vdif corresponds to the potential of the transmission signal on the transmission line 3 . That the differential voltage Vdif is "VH-VL" corresponds to that the potential of the transmission signal in the transmission line 3 is at a dominant level (hereinafter, dominant level). On the other hand, the fact that the differential voltage Vdif is 0 V corresponds to the fact that the potential of the transmission signal in the transmission line 3 is at a recessive level (hereinafter referred to as a recessive level). Each voltage value described above is an example of a standard value, and may be a value different from the standard value as long as it is within a predetermined allowable range, or a value with a certain range. good too.

However, since the waveforms of CANH and CANL are analog waveforms, for example, when a dominant signal is output as a transmission signal to the transmission line 3, CANH has a waveform that gradually rises from VM to VH, and CANL is a waveform of VM to VL. That is, in this case, the differential voltage Vdif has a waveform that gradually rises from 0V to 2V. For this reason, in the present embodiment, when the differential voltage Vdif is higher than the threshold voltage Vth, it is determined to be dominant, and when the differential voltage Vdif is lower than the threshold voltage Vth, it is determined to be recessive. The threshold voltage Vth is set to a value lower than the value of "VH-VL" (ie dominant level) and higher than 0V (ie recessive level).

The ECU 1 includes a controller 5 that performs processing related to communication, and a transceiver 7 that is connected to the transmission line 3 and performs transmission and reception of transmission signals.
The controller 5 outputs a transmission signal TXD that changes between high level and low level. The transmission signal TXD is an NRZ (that is, Non Return to Zero) signal. The high level of the transmission signal TXD and the reception signal RXD described later is, for example, 5V, and the low level of the transmission signal TXD and the reception signal RXD is, for example, 0V. Note that 5V and 0V are also examples of standard values, and values different from the standard values may be used as long as they are within a predetermined allowable range.

The high level of the transmission signal TXD and the reception signal RXD corresponds to, for example, logic "1" as a data value, and corresponds to a recessive level (that is, 0 V) as the potential of the transmission signal in the transmission path 3. The low level of the transmission signal TXD and the reception signal RXD corresponds to, for example, logic "0" as a data value, and the potential of the transmission signal in the transmission line 3 is dominant level (that is, "VH-VL"). handle. In this embodiment, the recessive level corresponds to the first level and the dominant level corresponds to the second level.

Therefore, when the transmission signal TXD changes from high level to low level, the potential of the transmission signal changes from recessive level to dominant level. Conversely, when the transmission signal TXD changes from low level to high level, the potential of the transmission signal changes from dominant level to recessive level.

Here, an example of a scene where the bit length of a transmission signal fluctuates due to the influence of external noise will be described with reference to FIG.
S1 is the waveform of the normal differential voltage Vdif that is not affected by external noise, and is the waveform when transmitting a 1-bit signal at a dominant level. The bit length determined to be dominant is between t1 and t3.

S2 is the waveform of the external noise. Note that although a sinusoidal external noise is exemplified here, the waveform of the external noise is not limited to this, and may be, for example, a pulse waveform.
S3 is a waveform obtained by synthesizing the waveform of the differential voltage Vdif affected by the external noise, that is, the waveform of the differential voltage Vdif of S1 and the waveform of the external noise of S2. In the example of FIG. 2, the synthesized waveform of S3 rises more slowly than the waveform of the normal differential voltage Vdif. The bit length determined to be dominant is between t2 and t3. That is, the bit length of the combined waveform of S3 is shorter than the bit length of the waveform of the normal differential voltage Vdif. If the bit length changes in this way, there is a possibility that the transmission signal on the transmission line 3 will not be correctly recognized. Therefore, the ECU 1 of the present embodiment has a function of adjusting the waveform transmitted to the transmission line 3 so as to suppress changes in bit length due to external noise, as will be described later.

Note that a period during which the potential of the transmission signal in the transmission line 3 changes from recessive to dominant and a period during which the potential of the transmission signal changes from dominant to recessive in a normal state when not affected by external noise are referred to as change periods, respectively. The change period includes a measurement period described later and an adjustment period described later.

Returning to FIG. 1 , the transceiver 7 includes a measuring section 11 , a transmitting section 12 and a receiving section 13 .
As shown in FIG. 3 , the measuring section 11 includes a measuring section 41 and a comparing section 42 .

The transmission signal TXD, CANH and CANL are input to the measurement unit 41 . In this embodiment, when the potential of the transmission signal changes from recessive to dominant, the measurement unit 41 causes the differential voltage Vdif between CANH and CANL to rise at the timing when the transmission signal TXD changes from high level to low level. The period until the measurement voltage Va is exceeded is defined as a measurement period, and the time length of this measurement period is measured. The measurement unit 41 outputs the value of the measured time length as the tilt measurement value Sm indicating the tilt during the measurement period. The rise measurement voltage Va is set to a value lower than the threshold voltage Vth and higher than 0 V (that is, recessive level).

In this embodiment, when the potential of the transmission signal changes from dominant to recessive, the measurement unit 41 detects the differential voltage Vdif between CANH and CANL from the timing when the transmission signal TXD changes from low level to high level. falls below the fall measurement voltage Vb as a measurement period, and the time length of this measurement period is measured. The measurement unit 41 outputs the value of the measured time length as the tilt measurement value Sm. Fall measurement voltage Vb is set to a value lower than the value of "VH-VL" (that is, dominant level) and higher than threshold voltage Vth.

As shown in FIG. 4, the comparison unit 42 determines the transmission signal based on the slope measurement value Sm output from the measurement unit 41 and the preset rising slope reference value RSr and falling slope reference value FSr. The degree of gradient of potential change is determined. The comparison unit 42 outputs to the adjustment unit 23 a slope result, which is the result of determining the degree of slope of the potential change of the transmission signal. The rise slope reference value RSr is set in advance from the viewpoint of the length of the period until the differential voltage Vdif rises and exceeds the measurement voltage Va in normal times when the potential of the transmission signal changes from recessive to dominant. . The falling slope reference value FSr is set in advance from the viewpoint of the length of the period until the differential voltage Vdif drops below the falling measurement voltage Vb in normal times when the potential of the transmission signal changes from dominant to recessive. ing. Hereinafter, the rising slope reference value RSr and the falling slope reference value FSr are also referred to as a slope reference value Sr when they are not distinguished from each other.

In this embodiment, the comparison unit 42 determines the degree of inclination of the potential change of the transmission signal in three stages. That is, the measurement slope Ms, which is the slope of the potential change of the transmission signal during the measurement period, is the amount of change in the potential of the transmission signal during the measurement period, that is, the absolute value of the potential difference between the recessive level and the rising measurement voltage Va, or the dominant level. It is a value obtained by dividing the absolute value of the potential difference from the drop measurement voltage Vb by the actually measured length of the measurement period, that is, the slope measurement value Sm. Although the value of the measured slope Ms is not actually calculated, the measured slope Ms is a value corresponding to the slope measured value Sm.

The fact that the slope measurement value Sm and the rise slope reference value RSr are the same means that the actual time required for the differential voltage Vdif to rise and exceed the rise measurement voltage Va was the same as the normal time. means. Similarly, the fact that the slope measurement value Sm and the falling slope reference value FSr are the same means that the actual time required for the differential voltage Vdif to fall below the falling slope measurement voltage Vb is the same as the normal time. means that it was That is, it means that the measured slope Ms was exactly the target slope Ts. The target slope Ts is the rate of change of the potential of the transmission signal in normal times when the potential of the transmission signal changes from recessive to dominant or when the potential of the transmission signal changes from dominant to recessive. When determining that the measured tilt value Sm and the reference tilt value Sr are the same, the comparing unit 42 outputs a signal indicating that the measured tilt Ms and the target tilt Ts are the same to the adjusting unit 23 as the tilt result. . Note that the inclination measurement value Sm and the inclination reference value Sr being the same do not mean that the inclination measurement value Sm and the inclination reference value Sr are strictly the same. For example, if the difference between the tilt measurement value Sm and the tilt reference value Sr is smaller than a predetermined value, the comparison unit 42 determines that the measured tilt Ms and the target tilt Ts are the same.

Further, the fact that the slope measurement value Sm is smaller than the rise slope reference value RSr means that the actual time required for the differential voltage Vdif to rise and exceed the rise measurement voltage Va was shorter than the normal time. means Similarly, the fact that the slope measurement value Sm is smaller than the falling slope reference value FSr means that the actual time required for the differential voltage Vdif to fall below the falling slope measurement voltage Vb is shorter than the normal time. means that That is, it means that the measured slope Ms is steeper than the target slope Ts. When determining that the measured tilt value Sm is smaller than the reference tilt value Sr, the comparing unit 42 outputs a signal indicating that the measured tilt Ms is steeper than the target tilt Ts to the adjusting unit 23 as the tilt result.

Further, when the slope measurement value Sm is larger than the rising slope reference value RSr, it means that the actual time required for the differential voltage Vdif to rise and exceed the measuring voltage Va is longer than the normal time. means. Similarly, the fact that the slope measurement value Sm is larger than the falling slope reference value FSr means that the actual time required for the differential voltage Vdif to fall below the falling measuring voltage Vb is longer than the normal time. That means. That is, it means that the slope Ms is gentler than the target slope Ts. When determining that the measured tilt value Sm is larger than the reference tilt value Sr, the comparing unit 42 outputs a signal indicating that the measured tilt Ms is gentler than the target tilt Ts to the adjusting unit 23 as the tilt result.

When the state of the measurement unit 41 is not yet measured or is being measured, the comparison unit 42 outputs a signal indicating that the determination has not yet been made to the adjustment unit 23 as the tilt result. The non-measurement state is an initial value state in which measurement has never been performed. A state in which measurement is in progress is a state in which the measurement period continues.

Returning to FIG. 1 , the transmitter 12 is connected to the transmission line 3 . The transmission unit 12 includes a first transistor 21 connected to the high-potential signal line 3a, a second transistor 22 connected to the low-potential signal line 3b, a transmission signal TXD input from the controller 5, and the measurement unit 11. and an adjustment unit 23 that drives the first transistor 21 and the second transistor 22 according to the inclination result input from the. In this embodiment, the first transistor 21 is a P-channel field effect transistor whose source is connected to the power supply Vcc, and the second transistor 22 is an N-channel field effect transistor whose source is grounded.

A driving voltage is input from the adjusting section 23 to the gates of the first transistor 21 and the second transistor 22 as control terminals. When the transmission signal TXD changes from high level to low level, the first transistor 21 changes CANH from VM to VH according to the value of the drive voltage (hereinafter referred to as drive voltage value) output by the adjustment unit 23. , the second transistor 22 changes CANL from VM to VL.

When the transmission signal TXD changes from low level to high level, the first transistor 21 changes CANH from VH to VM according to the drive voltage value output from the adjustment unit 23, and the second transistor 22 changes CANL. is changed from VL to VM.

Moreover, as shown in FIG. 5, the adjustment unit 23 includes a state machine 51 and a transmitter 52 .
Based on the transmission signal TXD from the controller 5 and the tilt result input from the measuring section 11 , the state machine 51 instructs the transmitter 52 on the drive voltage value to be output by the transmitter 52 . The drive voltage value indicated by the state machine 51 will be detailed later.

The transmitter 52 is connected to the gates of the first transistor 21 and the second transistor 22 . The transmitter 52 outputs the drive voltage value indicated by the state machine 51 to the gates of the first transistor 21 and the second transistor 22 .

Returning to FIG. 1 , the receiver 13 is also connected to the transmission line 3 . The receiving section 13 converts the transmission signal on the transmission path 3 into a reception signal RXD that changes between high and low levels, and outputs the reception signal RXD after conversion to the controller 5 .

[2. process]
[2-1. Adjustment processing in change from recessive to dominant]
The adjustment processing executed by the measurement unit 11 and the adjustment unit 23 will be described using the flowchart of FIG. 6 .

First, the adjustment processing when the potential of the transmission signal changes from recessive to dominant will be described. When the change of the transmission signal TXD from high level to low level is detected, the adjustment process of FIG. 6 is started.

First, in S101, the measurement unit 11 measures the tilt measurement value Sm. In addition, during the period from the start of measurement to the end of measurement, the measurement unit 11 outputs a signal indicating that the determination has not yet been made to the adjustment unit 23 as the tilt result. The state machine 51 of the adjustment unit 23 instructs the transmitter to output the same drive voltage value as the drive voltage value instructed in the adjustment period described later in the adjustment process executed when the potential of the transmission signal changed from recessive to dominant last time. 52. At this time, as shown in FIG. 7, the slope of the potential change of the transmission signal during the measurement period is the slope of the previous adjustment period.

At the very first timing when energization of the transmission line 3 is started, if the slope result indicates that the determination has not yet been made, the state machine 51 does not have the previous drive voltage value. Indicate the voltage value to the transmitter 52 . The default drive voltage value for rising is set within a range in which the signal on the transmission line 3 can be switched to dominant.

Subsequently, in S102, the measurement unit 11 determines whether or not the measured slope Ms and the target slope Ts are the same based on the slope measured value Sm and the rising slope reference value RSr.
If the measuring unit 11 determines in S102 that the measured tilt Ms and the target tilt Ts are the same, the measuring unit 11 sends a signal indicating that the measured tilt Ms and the target tilt Ts are the same to the adjusting unit 23 as the tilt result. Output. As shown in FIG. 7, the adjustment unit 23 keeps the slope of the potential change of the transmission signal during the adjustment period to the latest slope, that is, keeps the measured slope Ms. Specifically, the state machine 51 instructs the transmitter 52 to output the current drive voltage value as it is. At the drive voltage value output from the transmitter 52 during the measurement period, the drain current drivability (hereinafter referred to as current drivability) of the first transistor 21 and the second transistor 22 such that the measured slope Ms becomes the target slope Ts. because he was That is, the drive voltage value output from the transmitter 52 is the default drive voltage value for rise if the current drive voltage value is the default drive voltage value for rise, and the current drive voltage value is the default drive voltage value for rise. If it is the drive voltage value instructed in the adjustment period during execution of the adjustment process, it is the drive voltage value.

Note that the adjustment period is a period after the measurement period in the change period. As described above, the change period when the potential of the transmission signal on the transmission line 3 changes from recessive to dominant is the period during which the potential of the transmission signal on the transmission line 3 changes from recessive to dominant in a normal state not affected by external noise. This is the period during which it changes to dominant. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.

On the other hand, when the measurement unit 11 determines in S102 that the measured slope Ms and the target slope Ts are not the same, the process proceeds to S103, and the measured slope Ms is determined based on the slope measured value Sm and the rising slope reference value RSr. It is determined whether or not the inclination is greater than the target inclination Ts.

When the measurement unit 11 determines in S103 that the measured slope Ms is larger than the target slope Ts, the measured slope Ms is larger than the target slope Ts, that is, the measured slope Ms is steeper than the target slope Ts. is output to the adjustment unit 23 as the tilt result, and the process proceeds to S104.

In S104, as shown in FIGS. 7 and 8, the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes gentler. Specifically, the state machine 51 instructs the transmitter 52 to output a drive voltage value that reduces the current drive capability. For example, the transmitter 52 increases the drive voltage value output to the gate of the first transistor 21 from the current drive voltage value, and decreases the drive voltage value output to the gate of the second transistor 22 from the current drive voltage value.

The drive voltage value after adjustment is set within a range in which the signal on the transmission line 3 can be switched to dominant. At this time, for example, based on the default drive voltage value for rising, the drive voltage value to be output is set in advance in multiple steps, and the drive voltage value to be output is increased by one step for each adjustment process, or You can adjust it to lower it. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.

Returning to FIG. 6, on the other hand, when the measurement unit 11 determines in S103 that the measured slope Ms is smaller than the target slope Ts, it means that the measured slope Ms is smaller than the target slope Ts, that is, the measured slope Ms is equal to the target slope. A signal indicating that the slope is gentler than Ts is output to the adjustment unit 23 as the slope result, and the process proceeds to S105.

In S105, as shown in FIGS. 7 and 9, the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes steeper. Specifically, the state machine 51 instructs the transmitter 52 to output a drive voltage value that increases the current drive capability. For example, the transmitter 52 lowers the drive voltage value output to the gate of the first transistor 21 from the current drive voltage value and raises the drive voltage value output to the gate of the second transistor 22 from the current drive voltage value.

The drive voltage value after adjustment is set within a range in which the signal on the transmission line 3 can be switched to dominant. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.
After the adjustment process in FIG. 6 is finished, that is, while the dominant state continues, the adjustment unit 23 continues to output the same drive voltage value as during adjustment.

[2-2. Timing chart for change from recessive to dominant]
The behavior when the potential of the transmission signal changes from recessive to dominant at the very first timing when the transmission line 3 starts to be energized will be described with reference to the timing chart of FIG. 10 .

First, as shown in the first level, when the transmission signal TXD changes from high level to low level, the measurement unit 41 starts measurement at the timing when the transmission signal TXD changes as shown in the third level.

Also, as shown in the second row, the adjustment unit 23 outputs the default driving voltage value for rising at the timing when the transmission signal TXD changes. In addition, the driving voltage value to be output exemplifies the driving voltage value to be output to the gate of the second transistor 22 .

Then, the potential of the transmission signal changes from the recessive level to the dominant level. That is, the differential voltage Vdif gradually increases as shown in the fourth row.
Subsequently, the measurement unit 41 ends the measurement at the timing when the differential voltage Vdif rises and exceeds the measurement voltage Va.

In this case, since the slope measurement value Sm is larger than the rise slope reference value RSr, the adjusting unit 23 outputs a drive voltage value higher than the currently output drive voltage value, that is, the default drive voltage value for rise. do. Note that the adjustment unit 23 maintains the drive voltage value until the transmission signal TXD changes from low level to high level. The differential voltage Vdif remains dominant until the transmission signal TXD changes from low level to high level.

Further, at the timing when the transmission signal TXD changes from the high level to the low level from the second time onwards, the adjustment unit 23 outputs the same drive voltage value as the drive voltage value output during the adjustment period when the previous adjustment process was executed, Output during the measurement period instead of the default drive voltage value for rising.

[2-3. Adjustment Processing in Change from Dominant to Recessive]
Next, adjustment processing when the potential of the transmission signal changes from dominant to recessive will be described. When the change of the transmission signal TXD from low level to high level is detected, the adjustment process of FIG. 6 is started.

First, in S101, the measurement unit 11 measures the tilt measurement value Sm. In addition, during the period from the start of measurement to the end of measurement, the measurement unit 11 outputs a signal indicating that the determination has not yet been made to the adjustment unit 23 as the tilt result. The state machine 51 of the adjustment unit 23 instructs the transmitter 52 to output the same drive voltage value as the drive voltage value instructed in the adjustment period in the adjustment process executed when the potential of the transmission signal changed from dominant to recessive last time. instruct. At this time, the slope of the potential change of the transmission signal during the measurement period is the slope of the previous adjustment period.

Note that at the very first timing when energization of the transmission line 3 is started, if the slope result indicates that the determination has not yet been made, the state machine 51 does not have the previous drive voltage value. It instructs the transmitter 52 of the drive voltage value. The default driving voltage value for the falling edge is set within a range in which the signal on the transmission line 3 can be recessively switched.

Subsequently, in S102, the measurement unit 11 determines whether or not the measured slope Ms and the target slope Ts are the same based on the slope measured value Sm and the falling slope reference value FSr.
If the measuring unit 11 determines in S102 that the measured tilt Ms and the target tilt Ts are the same, the measuring unit 11 sends a signal indicating that the measured tilt Ms and the target tilt Ts are the same to the adjusting unit 23 as the tilt result. Output. The adjustment unit 23 keeps the slope of the potential change of the transmission signal during the adjustment period to the latest slope, that is, keeps the measured slope Ms. Specifically, the state machine 51 instructs the transmitter 52 to output the current drive voltage value as it is. That is, the drive voltage value output from the transmitter 52 is the default drive voltage value for falling if the current drive voltage value is the default drive voltage value for fall, and the current drive voltage value is the default drive voltage value for fall. If it is the drive voltage value indicated in the adjustment period when the previous adjustment process was executed, it is the drive voltage value.

Note that the adjustment period is a period after the measurement period in the change period. As described above, the change period in which the potential of the transmission signal on the transmission line 3 changes from dominant to recessive is the period during which the potential of the transmission signal on the transmission line 3 changes from dominant to recessive in a normal state not affected by external noise. It is a period of recessive change. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.

On the other hand, when the measurement unit 11 determines in S102 that the measured slope Ms and the target slope Ts are not the same, the process proceeds to S103, and the measured slope Ms is calculated based on the slope measured value Sm and the falling slope reference value FSr. is greater than the target inclination Ts.

When the measurement unit 11 determines in S103 that the measured slope Ms is larger than the target slope Ts, the measured slope Ms is larger than the target slope Ts, that is, the measured slope Ms is steeper than the target slope Ts. is output to the adjustment unit 23 as the tilt result, and the process proceeds to S104.

In S104, the adjustment unit 23 adjusts the gradient of the potential change of the transmission signal during the adjustment period to the gentler side. Specifically, the state machine 51 instructs the transmitter 52 to output a drive voltage value that increases the current drive capability. For example, the transmitter 52 lowers the voltage value output to the gate of the first transistor 21 below the current drive voltage value, and raises the voltage value output to the gate of the second transistor 22 above the current drive voltage value.

The drive voltage value after adjustment is set within a range in which the signal on the transmission line 3 can be recessively switched. At this time, for example, based on the default drive voltage value for falling, the drive voltage value to be output is set in advance in multiple steps, and the drive voltage value to be output is increased by one step for each adjustment process. Or you may adjust it to lower it. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.

Returning to FIG. 6, on the other hand, when the measurement unit 11 determines in S103 that the measured slope Ms is smaller than the target slope Ts, it means that the measured slope Ms is smaller than the target slope Ts, that is, the measured slope Ms is equal to the target slope. A signal indicating that the slope is gentler than Ts is output to the adjustment unit 23 as the slope result, and the process proceeds to S105.

In S105, the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes steeper. Specifically, the state machine 51 instructs the transmitter 52 to output a drive voltage value that reduces the current drive capability. For example, the transmitter 52 increases the drive voltage value output to the gate of the first transistor 21 from the current drive voltage value, and decreases the drive voltage value output to the gate of the second transistor 22 from the current drive voltage value.

The drive voltage value after adjustment is set within a range in which the signal on the transmission line 3 can be recessively switched. After that, the measurement unit 11 and the adjustment unit 23 terminate the adjustment processing in FIG.
After the adjustment process in FIG. 6 is completed, that is, while the recessive state continues, the adjustment unit 23 continues to output the same drive voltage value as during adjustment.

[3. effect]
According to the embodiment detailed above, the following effects are obtained.
(3a) When the adjustment unit 23 determines that the measured slope Ms is gentler than the target slope Ts, it adjusts the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes steeper. On the other hand, when the adjustment unit 23 determines that the measured slope Ms is steeper than the target slope Ts, it adjusts the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes gentler. According to such a configuration, the ECU 1 can reduce the amount of change in the bit length due to external noise compared to a configuration in which the slope of the potential change of the transmission signal during the adjustment period is not adjusted in a situation where the bit length varies due to, for example, external noise. can be suppressed.

(3b) The adjustment unit 23 adjusts the drive voltage value output to the transistors capable of changing the potential of the transmission signal in the transmission path 3, that is, the first transistor 21 and the second transistor 22, thereby increasing the transmission signal during the adjustment period. Adjust the slope of the potential change of With such a configuration, the ECU 1 can adjust the slope of the potential change of the transmission signal during the adjustment period with a simple configuration.

(3c) The measurement unit 11 measures the potential of the transmission signal from the timing when the level of the transmission signal TXD from the controller 5 changes until the potential of the transmission signal reaches the measurement threshold potential, that is, the rise measurement voltage Va or the fall measurement voltage Vb. shall be the measurement period. With such a configuration, the ECU 1 can easily determine the slope of the potential change of the transmission signal during the measurement period. In addition, the ECU 1 sets the period until the potential of the transmission signal reaches the threshold potential for measurement as the measurement period. Adjustment can begin before Vth is exceeded or undershot.

In this embodiment, the ECU 1 corresponds to the communication device, and the measuring section 11 and the transmitting section 12 correspond to the driving section.
[4. Other embodiments]
Although the embodiments of the present disclosure have been described above, it is needless to say that the present disclosure is not limited to the above embodiments and can take various forms.

(4a) In the above embodiment, the adjustment process is performed during both the period during which the potential of the transmission signal in the transmission line 3 changes from recessive to dominant and the period during which the potential changes from dominant to recessive. However, the configuration may be such that the adjustment process is executed in one of the periods.

(4b) In the above embodiment, when it is determined that the measured slope is gentler than the target slope Ts, a process of adjusting the slope of the potential change of the transmission signal during the adjustment period so that the slope becomes steeper; , when it is determined that the measured slope is steeper than the target slope Ts, the slope of the potential change of the transmission signal during the adjustment period is adjusted so that the slope becomes gentler. It has been executed. However, either one of the processes may be configured to be executed in the adjustment process.

(4c) In the above embodiment, from the timing when the level of the transmission signal TXD from the controller 5 changes until the potential of the transmission signal reaches the measurement threshold potential, that is, the rise measurement voltage Va or the fall measurement voltage Vb. is measured as the measurement period, and the slope measurement value Sm and the slope reference value Sr are compared to determine the degree of slope of the potential change of the transmission signal. However, for example, the period from the timing when the level of the transmission signal TXD from the controller 5 changes to the elapse of the measurement threshold time is set as the measurement period, and the potential of the transmission signal at the end of the measurement period is set as the slope measurement value, The degree of inclination of the potential change of the transmission signal may be determined by comparing a voltage reference value, which will be described later, as an inclination reference value.

Specifically, the measurement unit 41 starts measurement when the transmission signal TXD changes, and ends measurement when the threshold time for measurement is exceeded. When the potential of the transmission signal changes from recessive to dominant, the measurement threshold time is set to a time shorter than the period until the differential voltage Vdif exceeds the threshold voltage Vth under normal conditions. In addition, when the potential of the transmission signal changes from dominant to recessive, the threshold time for measurement is set to a time shorter than the period until the differential voltage Vdif drops below the threshold voltage Vth under normal conditions. The measurement unit 41 outputs the voltage value of the differential voltage Vdif at the timing when the measurement is finished to the comparison unit 42 as the slope measurement value.

The comparison unit 42 calculates the degree of slope of the potential change of the transmission signal based on the slope measurement value output by the measurement unit 41 and the rising voltage reference value and the falling voltage reference value preset as slope reference values. judge. The rise voltage reference value is set in advance from the viewpoint of the potential of the transmission signal when the threshold time for measurement in normal times has passed when the potential of the transmission signal changes from recessive to dominant. The falling voltage reference value is set in advance from the viewpoint of the potential of the transmission signal when the threshold time for measurement in normal times has passed when the potential of the transmission signal changes from dominant to recessive.

By comparing the inclination measurement value and the inclination reference value, the comparison unit 42 determines whether the measured inclination Ms is the same inclination as the normal time, the measured inclination Ms is steeper than the normal time, or the measured inclination Ms is slower than normal.

With such a configuration as well, the ECU 1 can easily determine the slope of the potential change of the transmission signal during the measurement period. Further, the ECU 1 sets the period until the potential of the transmission signal reaches the measurement threshold time as the measurement period. Adjustments can begin within a period of time when the bit length is available.

(4d) In the above embodiment, the configuration including two transistors, the first transistor 21 connected to the high-potential signal line 3a and the second transistor 22 connected to the low-potential signal line 3b, is illustrated. . However, the number of transistors provided is not limited to this. For example, a plurality of transistors having a smaller current capacity (that is, current driving capability) than the first transistor 21 are connected to the high-potential signal line 3a, and a transistor having a smaller current capacity than the second transistor 22 is connected to the low-potential signal line 3b. may be connected in plurality. In this case, the transmitter 52 is connected to the gate of each transistor, and the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period by varying the driving voltage value output to the gate of each transistor. may be adjusted.

(4e) In the above embodiment, in S101, the state machine 51 of the adjustment unit 23 changes the drive voltage value and The transmitter 52 was instructed to output the same drive voltage value. According to such a configuration, by taking over the previous drive voltage value, the measured slope Ms can be made to approach the target slope Ts, for example, in a situation where noise is generated that is continuously affected in the same way each time. The transmitter 52 can continue to output a stable drive voltage value.

However, the potential of the transmission signal is not always affected in the same way. Therefore, in S101, the state machine 51 of the adjustment unit 23 may output a default drive voltage value for rising each time during the measurement period, regardless of the previous drive voltage value.

Further, in S101, the state machine 51 of the adjustment unit 23 outputs the same drive voltage value as the drive voltage value instructed in the adjustment period in the adjustment process executed when the potential of the transmission signal changed from dominant to recessive last time. instructed the transmitter 52 to do so. However, for example, in S101, the state machine 51 of the adjustment unit 23 may output the default drive voltage value for falling every time during the measurement period, regardless of the previous drive voltage value.

(4f) In the above embodiment, the adjustment unit 23 continues to output the same drive voltage value as during adjustment while the dominant state continues after the adjustment process is completed. However, for example, the adjustment unit 23 changes the drive voltage value to be output to a drive voltage value that maximizes the output voltage allowed by the voltage between the gate and the source after a certain period of time within the period in which the dominant continues normally. may Further, in the above-described embodiment, the adjustment unit 23 continues to output the same drive voltage value as during adjustment while the recessive state continues after the adjustment process is completed. However, for example, the adjustment unit 23 changes the drive voltage value to be output after a certain period of time within the period in which the recessive state normally continues, to a drive voltage value that minimizes the output voltage allowed by the voltage between the gate and the source. You may

(4g) In the above embodiments, communication was made according to CAN FD. However, the communication protocol followed by the communication system installed in the vehicle is not limited to this.
(4h) In the above embodiment, the comparison unit 42 determines the degree of inclination of the potential change of the transmission signal in three stages regardless of the magnitude of the difference between the inclination measurement value Sm and the inclination reference value Sr. However, for example, the adjustment unit 23 may adjust the voltage value to be output according to the magnitude of the difference between the slope measurement value Sm and the slope reference value Sr. Specifically, when the period from the timing when the level of the transmission signal TXD from the controller 5 changes until the potential of the transmission signal reaches the threshold potential for measurement is measured as the measurement period, the slope measurement value Sm is greater than the slope reference value Sr, the greater the difference between the slope measurement value Sm and the slope reference value Sr, the steeper the slope of the potential change of the transmission signal during the adjustment period. Further, when the slope reference value Sr is larger than the slope measurement value Sm, the larger the difference between the slope measurement value Sm and the slope reference value Sr, the more the slope of the potential change of the transmission signal during the adjustment period. Adjust to be gentle.

Also, when the period from the timing when the level of the transmission signal TXD from the controller 5 changes until the measurement threshold time elapses is measured as the measurement period, the slope measured value is larger than the slope reference value. , the greater the difference between the slope measurement value and the slope reference value, the more moderate the slope of the potential change of the transmission signal during the adjustment period. Further, when the slope reference value is larger than the slope measurement value, the larger the difference between the slope measurement value and the slope reference value, the steeper the slope of the potential change of the transmission signal during the adjustment period. adjust to

More specifically, the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period so that the rate of change of the potential of the transmission signal during the entire change period approaches the rate of change of the target slope Ts. That is, the adjustment unit 23 adjusts the rate of change in the potential of the transmission signal over the entire change period to the target value, regardless of whether the potential of the transmission signal in the transmission line 3 changes from recessive to dominant or from recessive to dominant. The slope of the potential change of the transmission signal during the adjustment period is adjusted so as to approach the rate of change of the slope Ts. In either case, the adjustment unit 23 adjusts the slope of the potential change of the transmission signal during the adjustment period so that the rate of change of the potential of the transmission signal during the entire change period approaches the rate of change of the target slope Ts. It may be configured to

(4i) The function of one component in the above embodiment may be distributed as multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added, replaced, etc. with respect to the configuration of the other above embodiment.

DESCRIPTION OF SYMBOLS 1...ECU, 3...Transmission path, 5...Controller, 11...Measurement part, 12...Transmission part, 23...Adjustment part.

Claims (5)

A transmission signal that changes between a high level and a low level is input from a controller (5), and according to the transmission signal, the potential of the transmission signal in the transmission line (3) is set to a first level corresponding to the high level, a second level corresponding to the low level, and a drive unit (11, 12) configured to change the
The drive unit
A period during which the potential of the transmission signal in the transmission path starts changing from the first level and finishes changing to the second level , and starts changing from the second level and finishes changing to the first level. with at least one of the periods up to and including
The change period includes a measurement period and an adjustment period that is a period after the measurement period,
a measurement unit (11) configured to measure a slope of potential change of the transmission signal during the measurement period;
When it is determined that the measured slope, which is the slope of the potential change of the transmission signal measured by the measuring unit, is gentler than the target slope, the slope of the potential change of the transmission signal during the adjustment period is a process of adjusting the slope to a steeper side, and, when it is determined that the measured slope is steeper than the target slope, the slope of the potential change of the transmission signal during the adjustment period is moderated. and an adjusting unit (23) configured to perform at least one of: A communication device according to claim 1,
The adjustment unit adjusts the slope of the potential change of the transmission signal during the adjustment period by adjusting the value of the driving voltage output to the transistors (21, 22) capable of changing the potential of the transmission signal in the transmission path. coordinating, communication device. The communication device according to claim 1 or claim 2,
The communication device, wherein the measurement period is a period from the timing when the level of the transmission signal from the controller changes until the potential of the transmission signal reaches a threshold potential for measurement. The communication device according to claim 1 or claim 2,
The communication apparatus, wherein the measurement period is a period from the timing when the level of the transmission signal from the controller changes until the measurement threshold time elapses. The communication device according to any one of claims 1 to 4,
The adjustment unit is adapted to change a potential change rate of the transmission signal in the transmission line when the potential of the transmission signal changes from the first level to the second level and to change the potential of the transmission signal from the second level to the first level. a communication device that adjusts the slope of the potential change of the transmission signal during the adjustment period so that at least one of the rate of change of the potential of the transmission signal in the case approaches the target rate of change of the slope.

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