JP5035591B2 - Terminal control system - Google Patents

Description

  The present invention relates to a main control device and a terminal control system having a terminal device connected via a communication line capable of bidirectional communication with the main control device.

  A sensor system is known as such a terminal control system. In general, in a sensor system, a system is constructed using a microcomputer or the like as a main control device and a sensor as a terminal device. Then, the microcomputer issues a request for detection signal output to the sensor, an instruction for adjustment, and the like. In recent years, various sensors are mounted on many devices including vehicles, and the demand for accuracy is increasing. For this reason, the necessity to adjust the sensor incorporated in the system as a terminal device by control from the outside of the terminal device is increasing.

  Japanese Patent Application Laid-Open Publication No. 2004-151620, which is cited below, discloses a technique for adjusting (trimming) a semiconductor sensor device used as such a terminal device by external control. According to this, trimming is performed using the three terminals of the semiconductor sensor device. The three terminals are a first terminal for inputting a power supply voltage of 5 V, a second terminal for outputting a detection result of the sensor, and a third terminal for trimming. When the voltage (12V) input from the third terminal becomes higher than the power supply voltage (5V) input from the first terminal, the semiconductor sensor device shifts to the trimming mode. Then, the second terminal which was the output terminal becomes an input terminal, and trimming data is input from the second terminal. Trimming data is set in the semiconductor sensor device by inputting a clock pulse higher than the power supply voltage 5V (8V) from the first terminal in accordance with this data.

Japanese Patent No. 2720718 (6th to 13th paragraphs, FIGS. 1 and 3)

According to the technique described in Patent Literature 1, an inexpensive and compact trimming circuit can be obtained with a small number of terminals. However, a plurality of different voltages (5V, 8V, 12V) are required, and the power supply circuit becomes complicated. In addition, external control is required for the three terminals, and the control circuit may be complicated.
On the other hand, there is also a method in which data is input from one terminal used in the normal operation mode as in serial communication, and the clock is generated inside the terminal device which is the receiving side device. In this case, although the number of terminals is small and the power supply circuit is simple, there is a problem that resistance to external noise is low. When trimming is affected by external noise, a sensor as a terminal device is adjusted based on an incorrect value, and the reliability of the system is lowered.
As described above, in a terminal control system such as a sensor system, it is difficult to perform control such as adjustment of the terminal device from the main control device with a simple configuration with high reliability.

  The present invention has been made in view of the above problems, and an object thereof is to provide a terminal control system having a simple configuration and excellent noise resistance.

In order to achieve the above object, a terminal control system according to the present invention includes a main control device, a terminal device controlled by the main control device, and a communication line that connects the two devices so that bidirectional communication is possible. The terminal device can be switched between a first operation state in which a normal operation is performed and a second operation state including at least an adjustment operation in which the terminal device can be adjusted. It has a configuration.
That is, when the data transmitted from the main control device to the terminal device via the communication line satisfies both the first condition and the second condition, the terminal device changes from the first operation state to the second condition. It shifts to an operation state, It is characterized by the above-mentioned.

According to this configuration, the main control device can control the operation state of the terminal device using a bidirectional communication line used for normal communication between the main control device and the terminal device. Further, for example, data for adjustment can be easily transmitted from the main control device to the terminal device. Furthermore, since both the first condition and the second condition must be met for transition from the normal operation state, the possibility of erroneous transition to the second operation state including the adjustment operation due to external noise or the like is suppressed. can do.
Therefore, a terminal control system having a simple configuration and excellent noise resistance can be provided by this feature configuration.

  In the terminal control system of the present invention, the first condition is that the data is in a predetermined first logical state after a predetermined first time interval from the start of data transmission, and the second condition is: The data is in a predetermined second logical state after a predetermined second time interval from transmission of the first logical state.

According to this feature, one condition is constituted by a logic state and a time interval, and the operation state does not shift unless both the two conditions are met. Therefore, it is possible to suppress the possibility of erroneously shifting from the first operation state, which is the normal operation, to the second operation state due to the influence of external noise or the like.
Here, the first logic state and the second logic state may be different logic states.
For example, when the communication line is short-circuited to the power supply or the ground, one of the logic states is always wrong. Therefore, the operating state is not erroneously shifted, and a highly reliable system can be constructed.

  The terminal control system according to the present invention is characterized in that the first time interval and the second time interval are at least twice the sampling time of one data in the bidirectional communication.

  According to this feature, since the data indicating the first logic state and the data indicating the second logic state are not continuous in bidirectional communication, the possibility that both the logic states are aligned and affected by external noise is suppressed. Can do.

  In the terminal control system of the present invention, the terminal device changes from the first operation state to the second operation state after confirming that the first condition and the second condition are both satisfied a plurality of times. It is characterized by migrating.

  According to this feature configuration, by repeating the same communication a plurality of times, it is possible to increase the number of times that the transition condition is confirmed without changing the communication method or the data configuration. Therefore, it becomes easy to arbitrarily set the conditions for permitting the transition of the operation state according to the environmental conditions and applications, and the reliability and convenience of the system are improved.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a terminal control system according to the present invention will be described based on the drawings using an example applied to a sensor system that controls a sensor unit as a terminal device.
FIG. 1 is a block diagram schematically showing a configuration example of a terminal control system of the present invention. This terminal control system is a sensor system having an ECU (Electronic Control Unit) 1 corresponding to a main control device and a sensor unit 2 corresponding to a terminal device. The sensor unit 2 includes a detection unit 3 and a signal processing unit 4. In this example, the detection unit 3 is a load sensor that detects a load based on a change in resistance value. Of course, the present invention is not limited to this, and other sensors such as a pressure sensor can be applied. The signal processing unit 4 of this embodiment includes an amplifier 5, an A / D conversion unit 6, a trimming control unit 7, a ROM 8, a digital control unit 9, and a communication I / F unit 10. The signal processing unit 4 performs various signal processing on the detection result of the detection unit 3 and outputs the detection result as the sensor unit 2.

  The amplifier 5 performs impedance conversion and signal amplification on the output of the detection unit 3. The A / D converter 6 converts a signal at the subsequent stage of the amplifier 5 that is an analog signal into a digital signal. That is, the analog signal obtained by the detection unit 3 is amplified by the amplifier 5 and then converted into a digital signal by the A / D conversion unit 6. The detection signal converted into the digital signal is subjected to digital signal processing in the digital control unit 9, for example, matched with a predetermined communication format, and output to the ECU 1 via the communication I / F unit 10.

  The sensor unit 2 is wire-connected by three wirings of a power line PL, a ground line GL, and one bidirectional communication line CL. Supply of power to the sensor unit 2 is controlled by the ECU 1. Further, since there is one communication line CL, the ECU 1 and the sensor unit 2 communicate with each other by half duplex communication.

  Communication between the sensor unit 2 and the ECU 1 is performed alternately. The sensor unit 2 starts operation after power is supplied from the ECU 1 through the power line PL and the ground line GL. Thereafter, a request for detection signal output is issued from the ECU 1 to the sensor unit 2, and in response to this, the sensor unit 2 outputs a detection result to the ECU 1 via the communication line CL.

  A load sensor, a pressure sensor, or the like is a sensor that converts a mechanical physical quantity such as strain into an electrical signal. The obtained analog electric signal has characteristics such as a large DC component drift (so-called offset and zero point voltage deviation) and a large variation in sensitivity. Therefore, adjustment (trimming, gain adjustment, etc.) is necessary to function as a highly accurate sensor. In addition, sensors other than load sensors and pressure sensors (for example, optical sensors) generally have similar properties.

As described above, the signal adjustment is necessary for the sensor unit 2, and the communication line CL is used for this adjustment. For example, when an adjustment instruction request is issued from the ECU 1 via the communication line CL, the sensor unit 2 shifts from the normal operation mode (normal operation state) to the adjustment mode (adjustment operation state), and receives the adjustment data. It will be in an acceptable state. That is, the trimming control unit 7 can convert the output of the digital control unit 9 into an appropriate value using the conversion table of the ROM 8 according to the adjustment data input from the ECU 1.
Then, when the ECU 1 returns to the normal operation mode by an instruction from the ECU 1 again, the adjusted sensor output signal can be output to the ECU 1.

In this example, the case where the ECU 1 controls the sensor unit 2 as in the normal operation has been described. However, the present invention includes the case where the main control device is another adjusting device.
Further, the adjustment and trimming methods include the case of using other methods such as changing the reference voltage of the A / D converter 6 and changing the gain and offset voltage of the amplifier 5.

Next, a specific method for shifting the sensor unit 2 from the normal operation mode to the adjustment mode will be described. FIG. 2 is a time chart showing an example of the operating state transition condition of the present invention.
The logical state of the communication line CL is maintained at the HI level even during non-communication (during idling) by pulling up the communication line CL (not shown). At the start of communication, the transmission-side device, for example, the ECU 1 first outputs a start bit S1 that is a LO level signal. Since the logic of the communication line CL, which was at the HI level during non-communication, changes due to reception of the start bit S1, the receiving device, for example, the sensor unit 2, recognizes the start bit S1 and starts communication.
The ECU 1 outputs a signal B1 of HI or LO level (first logic state) after a predetermined first time interval T1 from the output of the start bit S1. The sensor unit 2 receives the signal B1 in the first logic state after the first time interval T1 from the reception of the start bit S1. This is the first condition.

Next, the ECU 1 outputs the signal B2 in the second logic state at the LO or HI level, that is, the logic opposite to the first logic state, after a predetermined second time interval T2 from the transmission of the signal B1. The sensor unit 2 receives the signal B2 in the second logic state after the second time interval T2 from the reception of the signal B1. This is the second condition.
Of course, it is possible to set the second condition when the signal B1 in the first logic state and the signal B2 in the second logic state have the same logic. However, for example, when the communication line CL is short-circuited with the power source or the ground, the matching condition between the first and second logic states may be satisfied regardless of the transmission contents from the ECU 1. If the first logic state and the second logic state are different logic states, such a problem can be prevented and a highly reliable system can be constructed.
As described above, when the first condition and the second condition are satisfied, the sensor unit 2 shifts from the normal operation mode to the adjustment mode.

FIG. 3 is a time chart showing a specific example of a communication form for implementing the transition condition of FIG.
As described above, the serial communication data transmitted from the ECU 1 as the transmission side device via the communication line CL is at the HI level in the idling state. When the communication is started, the ECU 1 first transmits LO level communication data as the start bit S1 (period b1).
Then, the data bit D is transmitted following the start bit S1 (period b2). The data bit D is 8-bit data in this embodiment. The data bit D is transmitted in combination with HI / LO according to the data content.
When the transmission of the data bit D is completed, the parity bit P corresponding to the transmission data is transmitted (period b3). The parity as the error correction code includes an even parity and an odd parity, which are predetermined as the specifications of the terminal control system.
Finally, a HI level signal is transmitted as the stop bit S2 (period b4), and the idling state becomes the HI level again.

Here, the third data bit D ₂ from the head is a signal B1 indicating the first logic state, and the sixth data bit D ₅ is a signal B2 indicating the second logic state. From start bit S1 to the data bit D ₂ is a first time interval T1, the data bit D ₂ to D ₅ is the second time interval T2.

On the other hand, the sensor unit 2 as the receiving side device detects that the communication data has changed from HI to LO, and recognizes that the start bit S1 has been transmitted from the ECU1.
For detecting the state where the start bit S1 is LO, a method of detecting the falling edge of the communication signal by edge detection is employed. Then, when a predetermined time elapses from this detection, a sampling pulse as shown in the lower part of FIG. 3 starts to be generated. Thereafter, a predetermined number of sampling pulses are generated for each data pitch T0 corresponding to a preset communication speed. Since the number of bits received in one communication is determined as a specification of the terminal control system, a number of sampling pulses corresponding to the number of bits is generated.

In the present embodiment, communication data is composed of one start bit S1, one parity bit P, and one stop bit S2 and 8 data bits D. Accordingly, a total of 11 pulses corresponding to the total number of bits of these communication data are generated.
For example, the rising edge of the sampling pulse is a strobe point for receiving communication data. In this embodiment, an example is shown in which a stable timing near the center of each bit becomes a strobe point.

  In the example shown in FIG. 3, the first time interval T1 and the second time interval T2 are three times the data sampling time T0. The first temporary interval T1 and the second time interval T2 are effective when they are more than twice the sampling time of one data in bidirectional communication. If it is twice or more, the data bit D indicating the first logic state and the data bit D indicating the second logic state are not continuous. Therefore, it is possible to suppress the possibility that both logical states are aligned and affected by external noise.

Further, the series of communication data shown in FIG. 3 may be used a plurality of times to shift from the first operation state to the second operation state. That is, the sensor unit 2 may make a transition from the first operation state to the second operation state after confirming that the first condition and the second condition are satisfied a plurality of times.
In this way, it is possible to increase the number of times to check whether or not the migration condition is satisfied without changing the communication method or data configuration. Therefore, it becomes easy to arbitrarily set the conditions for permitting the transition of the operation state according to the environmental conditions and applications, and the reliability and convenience of the system are improved.

  As described above, according to the present invention, a terminal control system having a simple configuration and excellent noise resistance can be provided.

The block diagram which shows typically the structural example of the terminal control system of this invention Time chart showing an example of conditions for shifting operating states FIG. 2 is a time chart showing an example of a communication mode that implements the transition condition of FIG.

Explanation of symbols

1: ECU (main control unit)
2: Sensor (terminal device)
CL: Communication line S1: Start bit (transmission start)
S2: Stop bit B1: First logic state B2: Second logic state T0: Sampling time T1: First time interval T2: Second time interval

Claims (3)

A main control device, a terminal device controlled by the main control device, and a communication line connecting the two devices so as to be capable of bidirectional communication, a first operation state in which normal operation is performed, and at least the terminal device A terminal control system capable of switching the operation state of the terminal device between a second operation state including an adjustable adjustment operation,
When the data transmitted from the main control device to the terminal device via the communication line satisfies both the first condition and the second condition, the terminal device changes from the first operation state to the second operation state. migrated to,
The first condition is that the data is in a predetermined first logical state after a predetermined first time interval from the start of transmission of the data, and the second condition is predetermined from the transmission of the first logical state. der Ru terminal control system that the data after the second time interval is a predetermined second logic state. 2. The terminal control system according to claim 1 , wherein the first time interval and the second time interval are at least twice the sampling time of one data in the bidirectional communication. The terminal device, after the first condition and said second condition is a plurality of times to confirm that filled both, from the first operating state according to claim 1 or 2 shifts to the second operating state Terminal control system.

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