JPH08307478A - Serial communication equipment - Google Patents

Abstract

PURPOSE: To communicate with not only serial communication equipments having a prescribed signal voltage level but also serial communication equipments having different signal voltage levels. CONSTITUTION: An engine controller 1 is provided with a control circuit 2 consisting of a microcomputer and performs the processing or engine control by a program and performs serial communication with diagnostic devices 3 and 4 connected to terminals 5a and 5b. Diagnostic devices 3 and 4 transmit and receive serial signals with 5V and 12V voltage levels respectively in accordance with communication protocol different from each other. An interface circuit 7 converts the voltage level from 12V to 5V to connect the terminal 5b and the control circuit 2. The capture input terminal of the control circuit 2 is connected to the interface circuit 7 to detect the connection of the diagnostic device 4. Thus, the connected diagnostic device 3 or 4 is automatically detected to realize the serial communication by the corresponding communication protocol whichever diagnostic device is connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial communication device for serially communicating with a serial communication device having a predetermined communication format when the serial communication device is externally connected.

[0002]

2. Description of the Related Art In recent years, electronic control of vehicles has progressed, and various functions have come to be controlled by electronic devices using microcomputers. Along with this, in addition to the original vehicle control function, a self-diagnosis function of the control system using the functions of the microcomputer, a communication function with other control devices and external diagnosis devices, etc. have been developed and used. Is coming.

Under such circumstances, no matter how high-level the microcomputer is, hardware restrictions are unavoidable. Depending on the number of serial communication ports provided in the microcomputer to be used, it is possible to connect the communication devices. There is also a situation where the number is limited.

As a solution in such a case, for example, there is a serial signal switching method as disclosed in Japanese Patent Laid-Open No. 4-203343. That is, in this device, a code signal for switching external communication devices is included in a signal for performing serial communication, whereby serial communication can be performed corresponding to a plurality of external communication devices.

[0005]

However, in the conventional configuration as described above, for example, each of the external communication devices to be connected must have the same communication protocol, and the signal form is unified. Since it is necessary to use an external communication device having a communication protocol and a signal form with different specifications, the user must prepare an external communication device corresponding to it, which is very inconvenient. Met.

The present invention has been made in view of the above circumstances, and an object thereof is to enable communication with serial communication devices having different signal voltage levels in addition to serial communication devices having a predetermined signal voltage level. It is to provide a serial communication device.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a serial communication device configured to perform serial communication with a serial communication device having a predetermined communication format when the serial communication device is connected from the outside. An input unit to which a serial communication device that performs serial communication of a different format from the communication device can be connected, a signal level conversion unit that converts an input level of a serial communication signal input via the input unit to a predetermined level, and the input. A serial communication signal is inputted through the unit, and a detecting means for detecting the serial communication signal and a communication control means for performing serial communication of a corresponding format when the detecting signal is given from the detecting means are provided. (Claim 1).

Further, the communication control means may be composed of a microcomputer having a set of input / output ports capable of serial communication (claim 2).

[0009]

According to the serial communication device of the first aspect, when the serial communication device connected to the outside performs serial communication of the same format, the serial communication is executed as it is, and the serial communication is performed on the input section. When serial communication devices of different formats are connected, the conversion means converts the input level of the serial communication signal into a predetermined level, and the input signal is input to the communication control means. Based on the detection signal from the detection means, serial communication is performed in a communication format corresponding to this. As a result, even if serial communication devices of different formats are connected, it becomes possible to reliably perform serial communication.

According to the serial communication device of the second aspect, since a plurality of serial communication devices connected from the outside are not connected at the same time, the micro communication device having a set of input / output ports for serial communication. Even if it is configured by a computer, it can be easily implemented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an automobile engine control device will be described below with reference to the drawings. For example, in order to diagnose the control state of the engine control device of the automobile, data is transmitted and received by connecting a tester and performing serial communication. In this case, the tester is a user. Since different communication formats may be used depending on the case, it is configured to enable serial communication corresponding to them.

The engine control device 1 comprises a control circuit 2 as a communication control means composed of a microcomputer, a ROM, a RAM, etc., and a program for controlling the drive of an engine (not shown) is provided in the control circuit 2. Is stored inside, and drive control of the engine is performed based on input data from various sensors. The control circuit 2 is configured to include input / output terminals RXD and TXD for serial communication and a capture input terminal IC.

As the diagnostic device connected from the outside, for example, a diagnostic device 3 using a serial communication signal (see FIG. 5) whose signal level is set to 5V and a signal level of 12 are used.
It is assumed that the diagnostic device 4 uses a serial communication signal set to V (see FIG. 6A), and the engine control device 1 has a terminal 5a to which these diagnostic devices 3 and 4 can be connected.
5b is provided. The control circuit 2 of the engine control device 1 is configured to use a signal whose signal level is internally set to 5V.

In this case, the serial communication signal is generated for communication by performing a predetermined conversion operation on a signal which is normally processed in parallel inside the microcomputer. For example, FIG. 5 and FIG. 6A. In the example shown in (1), the 8-bit data D0 to D7 are generated as a serial signal in which the data D0 to D7 are sequentially arranged with the start bit as the head.

Further, the engine control unit 1 has a terminal 5
Interface circuits 6 and 7 are provided between a and 5b. That is, in the interface circuit 6, the terminal 5a is connected to the buffer amplifiers 6a and 6a.
Input terminal R of the engine control device 1 via the series circuit of b
It is connected to XD and is connected to the output terminal TXD via a series circuit of buffer amplifiers 6c and 6d. Further, in the interface circuit 7, the terminal 5b is connected to the engine control device 1 via the series circuit of the buffer amplifiers 7a and 7b.
Connected to the input terminal RXD of the buffer amplifiers 7c, 7
It is connected to the output terminal TXD via the series circuit of d.

The interface circuit 6 sends and receives signals between the terminal 5a and the input / output terminals RXD and TXD at a voltage level of 5V, and the interface circuit 7 receives signals from the terminals 5b and 12V. Is input, as shown in FIG. 6B, the buffer amplifiers 7a,
The signal having the voltage level of 5V is converted through 7b and applied to the input terminal RXD of the engine control device 1, and the output terminal TXD.
The signal of the voltage level of 5V from the buffer amplifier 7c,
7d converts the signal to a voltage level of 12V and the terminal 5
It is designed to output to b.

The common connection point of the buffer amplifiers 7a and 7b of the interface circuit 7 is connected to the capture input terminal IC of the control circuit 2. The control circuit 2 is
When a signal is input from the capture input terminal IC, as will be described later, according to a program, it is detected that the diagnostic device 4 is connected to the terminal 5b and the serial communication is started.

Next, the operation of this embodiment will be described with reference to FIGS. 2 to 4 are flowcharts of programs for performing serial communication. In the engine control device 1, the control circuit 2 is
When the power is turned on and the control program is started, various initial setting operations are performed (step S1). in this case,
In addition to the initial setting operation for engine control, the control circuit 2 performs initial setting operations such as permitting the start of serial communication function, permitting interrupt by capture input, and clearing flags.

After that, if there is no serial communication interrupt, the control circuit 2 executes the normal engine control process in the following step S2. At this time, the control circuit 2 activates the engine control, so that the interrupt of the serial communication is prohibited until the timer is started and the timer time exceeds 5 seconds.

When the timer time has elapsed for 5 seconds, the control circuit 2 determines "YES" in step S3 and moves to step S4 to reclear the serial communication related flags and interrupt by capture input. After that, the steps S2 to S4 are repeatedly executed, and the engine control process is performed while accepting the interrupt of the serial communication.

Now, in such a state, for example, the terminal 5b
When the diagnostic device 4 is connected to and the serial communication interrupt occurs, the control circuit 2 operates as follows. That is, first, by connecting the diagnostic device 4 to the terminal 5b, the detection signal is input to the control circuit 2 from the capture input terminal IC.

Then, the control circuit 2 comes to execute the capture input interrupt program shown in FIG. The control circuit 2 detects the timing when the input detection signal falls (step T1) and sets the value of the flag F to "1".
(Step T2), other interrupt processing is prohibited (step T3), and the process returns to the main program.

Since the diagnostic device 4 is connected to the terminal 5b and the serial communication signal is input, the control circuit 2 thereafter receives the serial signal input terminal RX.
When a serial communication signal is input from D, the serial communication processing program shown in FIG. 4 is executed in response to this. In this case, the voltage level of the serial signal input to the serial signal input terminal RXD of the control circuit 2 is converted to 5V through the interface circuit 7 (see FIG. 6B), but the communication protocol is the diagnostic device. The format is different from the one in No. 3.

The control circuit 2 first confirms the presence or absence of an error in the communication signal (step P1). If an error has occurred, the program is terminated, the process returns to the main program, and the engine control process is executed until the serial communication interrupt occurs again. If no error has occurred, the control circuit 2
When it is determined that the reception is the reception, the process proceeds to step P2, and when it is determined that the reception is the reception, the process proceeds to step P3 to determine whether the value of the flag F is "1".

In this case, the value of the flag F is set to "1" by the above-mentioned interrupt program by the capture input interrupt.
Since it is set to, the control circuit 2 is set to "YES" here.
If it is determined that the diagnostic device 4 is connected, the process proceeds to step P4. In Step P4, the control circuit 2 comes to accept the serial communication signal according to the communication protocol set in advance corresponding to the control device 4. When the reception of the serial signal is completed (step P5), the control circuit 2 shifts to step P7 via steps P6 and P2 for subsequent transmission.

Similarly, the control circuit 2 determines that the flag F is "1" (step P7), and performs the process for transmitting the serial signal corresponding to the diagnostic device 4 (step P8). , When the transmission is completed (Step P
9) Clear the timer that was running (step P
10) Return to the main program. Thereby, the control circuit 2 corresponds to the serial communication signal input from the diagnostic device 4 and outputs the serial signal output terminal TXD.
Then, the serial signal for transmission is output from and the communication processing is ended. The serial signal having a voltage level of 5V output from the serial signal output terminal TXD is transmitted from the terminal 5b to the diagnostic device 4 as a serial signal increased to a voltage level of 12V via the interface circuit 7.

In the above case, when the diagnostic device 3 is connected instead of the diagnostic device 4, the control circuit 2 operates as follows.
Since there is no capture input interrupt, the capture input interrupt program of FIG. 3 is not executed. Therefore,
Since the value of the flag F remains "0", the control circuit 2 executes step P when the serial signal is input and the program of the serial communication process is executed.
When it is determined to be "NO" in step 3, the process proceeds to step P11. Then, in step P11, the control circuit 2
Performs the reception processing of the serial signal by the communication protocol corresponding to the diagnostic device 3, and when it is transmitted, the step P
Even in No. 7, it is determined to be "NO", and the process proceeds to Step P12 to perform the serial signal transmission process corresponding to the diagnostic device 3.

When the control circuit 2 returns to the main program and executes step S4, the value of the flag F is cleared (F ← “0”) and the interrupt of serial communication is permitted again. Thereby, the serial communication by the diagnostic device 3 or the diagnostic device 4 is accepted.
As a result, regardless of which diagnostic device 3 or 4 is connected, the engine control device 1 is
Will be able to do serial communication with.

According to the present embodiment as described above, the interface circuit 7 is provided so that the diagnostic device 4 whose voltage level of the communication protocol and the serial communication signal is set to a level different from 12 V can be connected. Since this is determined by converting the level and performing the capture input interrupt process, the voltage level of the serial communication signal is 12 with different communication protocols.
Even if the V diagnostic device 3 is used, this can be automatically detected and serial communication can be performed, so that any of the diagnostic devices 2 and 3 for exchanging self-diagnosis data can be used. , The usability is improved.

Further, according to the present embodiment, the microcomputer constituting the control circuit 2 as the communication control means can be provided with one set as a serial signal input / output terminal. The configuration for obtaining the above-mentioned effects can be realized easily and inexpensively without using a new configuration.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. The control circuit 2 may be configured to perform edge detection level determination instead of capture input.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention.

[Figure 2] Flow chart of the main program

FIG. 3 is a flowchart of a capture input interrupt program.

FIG. 4 is a flowchart of a serial communication processing program.

FIG. 5 is a time chart of a serial signal of the diagnostic device.

FIG. 6 is a time chart of serial signals of different diagnostic devices and a time chart after voltage level conversion.

[Explanation of symbols]

1 is an engine control device, 2 is a control circuit (communication control means), 3 is a diagnostic device (serial communication device), 4 is a diagnostic device (different serial communication device), 5b is a terminal (input unit), 6 is an interface circuit, Reference numeral 7 is an interface circuit (conversion means).

Claims (2)

[Claims] 1. A serial communication device configured to perform serial communication with a serial communication device of a predetermined communication format when the serial communication device is externally connected, wherein the serial communication device performs serial communication of a different format from the serial communication device. An input section to which a communication device can be connected, a signal level conversion means for converting an input level of a serial communication signal input through the input section to a predetermined level, and a serial communication signal input through the input section A serial communication device comprising: detection means for sometimes detecting this; and communication control means for performing serial communication in a corresponding format when a detection signal is given from the detection means. 2. The serial communication device according to claim 1, wherein the communication control means is composed of a microcomputer having a set of input / output ports capable of serial communication.