Detection device

A detection device is connected to a plurality of communication devices by a communication line. The detection device has a reception unit, a measurement unit, and a detection unit. The reception unit receives signals with prescribed pulse widths transmitted from the plurality of communication devices, respectively. The measurement unit measures the pulse widths of the signals received by the reception unit. The detection unit is configured to detect the communication device disposed near a terminal end of the communication line as a terminal-end communication device on the basis of the plurality of pulse widths measured by the measurement unit.

TECHNICAL FIELD

The present invention relates to a detection device.

Priority is claimed on Japanese Patent Application No. 2018-179753, filed Sep. 26, 2018, the content of which is incorporated herein by reference.

BACKGROUND ART

In the related art, there is a communication system in which a plurality of cordless extension units are bus-connected to one base device via a communication line. For example, in the case of an air-conditioning system for business use installed in a large-size building or the like, the cordless extension unit is an indoor unit, and the base device is, for example, a management device such as an outdoor unit or an air-conditioning management device at a center, or the like. In such an air-conditioning system, information related to an operation of each of the connected indoor units (for example, set temperature information, sensor information, and the like) is acquired sequentially and managed collectively in the management device. In addition, in such an air-conditioning system, operations of the plurality of indoor units can also be controlled collectively by the management device. For example, in the office building, it is possible to collectively start (ON) operations of the indoor units in the office building before the attendance time of workers and collectively stop (OFF) operations of all the indoor units after leaving time according to a previously set schedule using the function. Accordingly, convenience is improved for an air-conditioning manager or the like.

Incidentally, in the communication system in which the above-mentioned bus connecting system is employed, terminating resistors are generally set in the base device and the cordless extension units disposed at a terminal end of a communication line. When a communication speed is increased and a communication wiring length is increased, an influence of the reflection of the communication signal at the terminal end may become large, and a signal waveform may be disturbed. On the other hand, since terminating resistors that are constant and appropriate for communication are set in the base device and the cordless extension units disposed close to the terminal end of the communication line, reflection of the signal can be minimized, and the communication can be performed without disturbing a signal waveform.

However, if a terminating resistor is installed temporarily, for example, when the number of cordless extension units connected to the communication line is changed due to expansion or removal or when there is replacement with a communication line of a different length or type, the cordless extension unit that sets the terminating resistor must be changed or the setting must be changed every time. In the related art, in the air-conditioning system for business use installed in a large-size building or the like, since a manager or the like of the air-conditioning system performs setting of the terminating resistor, there is a need to find the indoor unit disposed near the terminal end of the communication line. However, in such an air-conditioning system, since a plurality of indoor units are connected to an elongated communication wiring, it is not easy to manually find the indoor unit disposed near the terminal end of communication line from the indoor units.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Problems to be Solved by the Invention

In order to solve the above-mentioned problems, the present invention is directed to providing a detection device capable of detecting a communication device of a terminal end of a communication line.

Means for Solving the Problems

A detection device of an embodiment is connected to a plurality of communication devices by a communication line. The detection device has a reception unit, a measurement unit and a detection unit. The reception unit receives signals with prescribed pulse widths transmitted from the plurality of communication devices. The measurement unit measures the pulse widths of the signals received by the reception unit. The detection unit is configured to detect the communication devices disposed near the terminal end of the communication line as terminal-end communication devices on the basis of the plurality of pulse widths measured by the measurement unit.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detection device of an embodiment will be described with reference to the accompanying drawings.

First Embodiment

Hereinafter, a configuration of an air-conditioning system100according to a first embodiment will be described.

FIG.1is the entire configuration view of the air-conditioning system100according to the first embodiment. The air-conditioning system100shown inFIG.1is, for example, an air-conditioning system installed in an office building. As shown inFIG.1, the air-conditioning system100is configured to include an outdoor unit1that is an outdoor unit of an air-conditioner, and an indoor unit2-1, an indoor unit2-2and an indoor unit2-3that are indoor units of the air-conditioner. Further, in the following description, when there is no need to describe the indoor unit2-1, the indoor unit2-2and the indoor unit2-3in a distinguishable manner, they are simply referred to as “the indoor unit2.” The outdoor unit1and the indoor units2are configured as a refrigerating cycle by being connecting by a coolant pipeline. In addition, the outdoor unit1and the indoor units2are connected by a communication line30, and the outdoor unit1and the indoor units2can exchange signals.

In this way, the air-conditioning system100includes the outdoor unit1and the plurality of indoor units2. The outdoor unit1collectively controls operations of the plurality of indoor units2. Further, the number of the plurality of indoor units2controlled by the outdoor unit1is not limited to three, and an arbitrary number of indoor units may be used.

The outdoor unit1includes the communication device10that is a base device on communication. In addition, the indoor unit2-1, the indoor unit2-2and the indoor unit2-3include a communication device20-1, a communication device20-2and a communication device20-3that are cordless extension units for communication, respectively. Further, in the following description, when there is no need to describe the communication device20-1, the communication device20-2and the communication device20-3in a distinguishable manner, they are simply referred to as “a communication device20.”

As shown inFIG.1, the communication device10, the communication device20-1, the communication device20-2and the communication device20-3are connected by the communication line30with a bus connecting system. Since only the outdoor unit1is disposed outdoors and the indoor units2are installed indoors, the communication device10of the outdoor unit1is conventionally installed at a position near one terminal end of the communication line30.

The communication device10has a communication function of being configured to perform communication with the plurality of communication devices20. For example, the communication device10can acquire information showing an operating status of the indoor unit2or can acquire information showing a temperature or a humidity of a room in which the indoor unit2is installed by receiving a signal transmitted from the communication device20. In addition, the communication device10can control an operating state of the indoor unit2via, for example, the communication device20by transmitting the signal to the communication device20.

The communication device10includes a terminating resistor11, which will be described below. Accordingly, the communication device10always has a function of a terminating device. In addition, as described below in detail, the communication device10also includes a function as a detection device configured to detect the communication device20of the indoor unit installed near the terminal end on the communication line30.

In addition, the communication device20includes a terminating resistor setting unit21provided with a terminating resistor, which will be described below. The terminating resistor setting unit21performs switching of settings of the terminating resistor or release of the settings on the basis of a command transmitted from the communication device10(the detection device). Accordingly, the communication device20may or may not have a function as a terminating device.

Both of the communication device10and the communication device20can perform communication by switching between communication in a high speed communication mode that is a mode of performing communication at a high speed and communication in a low speed communication mode that is a mode of performing communication at a speed relatively lower than the high speed.

In an initial state before the air-conditioning system100is operated, the terminating resistor is in a state in which the setting released in the terminating resistor setting unit21of all of the communication devices20. Accordingly, in the initial state, since none of the communication devices20have a function of a terminating device, reflection of the signal transmitted by the communication line30is likely to occur, and the signal waveform is likely to be disturbed. Especially when communication is performed at a high speed, since the influence of the reflection of the signal tends to be large, in the initial state, both of the communication device10and the communication device20are set to a low speed communication mode.

The communication device10performs control such that reflection of the signal transmitted by the communication line30can be minimized and communication with the communication device20can be performed at a high speed communication mode. Specifically, the communication device10includes a detection function operating as a detection device and configured to detect and identify one of the communication devices20(i.e., the communication device20-3) disposed near the terminal end of the communication line30. Then, the communication device10transmits a command for switching a state in which a terminating resistor is set to the terminating resistor setting unit21of the detected communication device20. As described below, while the communication device (detection device)20should be able to identify the communication device20disposed closest to the terminal end of the communication line30, since the plurality of communication devices20cannot be distinguished when they have similar wiring lengths, one of the communication devices20disposed near the terminal end is identified. This also achieves the purpose of improving stability of sufficient communication (waveform).

The terminating resistor setting unit21of the communication device20disposed near the terminal end of the communication line30is switched to a state in which the terminating resistor is set according to the received command. Accordingly, the communication device20disposed near the terminal end of the communication line30becomes a terminating device. Then, the terminating resistor that is an appropriate constant for communication can be set in the communication device10and the communication device20disposed near both of the terminal ends of the communication line30, reflection of the signal can be minimized, and the communication can be performed without disturbing the signal waveform.

Hereinafter, a method of detecting the communication device20disposed closest to the terminal end of the communication line30due to the function as the detection device of the communication device10will be described.

First, the communication device10commands output of pulse signals with a prescribed pulse width to the communication devices20in sequence. The communication device10receives the pulse signals output from the communication devices20, and measures pulse widths of the pulse signals. Then, the communication device10identifies the shortest pulse width of the plurality of measured pulse widths. The communication device10detects the communication device20that has transmitted the pulse signal with the specified pulse width as the communication device20disposed at the terminal end of the communication line30or near the terminal end.

FIGS.2,3,4and5are schematic views showing detection of the communication device20disposed near the terminal end of the communication line30by the communication device10according to the first embodiment.

As shown inFIG.2, for example, when a pulse signal with a prescribed pulse width w is transmitted from the communication device20-1, there is a pulse signal A that reaches the communication device10directly. In addition, in the initial state, since reflection of the signal occurs when the terminating resistor is not set in any of the communication devices20, as shown inFIG.2, there is a pulse signal B that reflects and reaches the communication device20-3disposed at the terminal end of the communication line30.

In this case, a moving distance until the pulse signal B is transmitted from the communication device20-1to the communication device10is greater than a moving distance until the pulse signal A is transmitted from the communication device20-1to the communication device10. For this reason, the pulse signal B reaches the communication device10later than the pulse signal A. Accordingly, the communication device10recognizes two pulse signals (the pulse signal A and the pulse signal B) that overlap each other with a time lag as one pulse signal. That is, as shown inFIG.2, the communication device10recognizes that a pulse signal with a pulse width x (x>w) in which the pulse signal A and the pulse signal B overlap each other has been received.

FIG.3shows a pulse signal recognized by the communication device10when the pulse signal with the pulse width w is transmitted from the communication device20-1. In this case, as shown inFIG.2, the pulse width with the pulse signal recognized by the communication device10is x (x>w).

FIG.4shows a pulse signal recognized by the communication device10when the pulse signal with the pulse width w is transmitted from the communication device20-2. When the pulse signal is transmitted from the communication device20-2, a difference between the moving distance until the pulse signal B is transmitted from the communication device20-1to the communication device10and the moving distance until the pulse signal A is transmitted from the communication device20-1to the communication device10is smaller than that in the case in which the pulse signal is transmitted from the communication device20-1. For this reason, the time lag between the two overlapping pulse signals (the pulse signal A and the pulse signal B) is smaller than that in the case of the pulse signal shown inFIG.3. For this reason, as shown inFIG.4, the communication device10recognizes that a pulse signal with a pulse width y (x>y>w) in which the pulse signal A and the pulse signal B overlap each other is received.

FIG.5shows a pulse signal recognized by the communication device10when the pulse signal with the pulse width w is transmitted from the communication device20-3. When the pulse signal is transmitted from the communication device20-3, since the communication device20-3is disposed nearest the terminal end of the communication line30, reflection of the signal does not occur. That is, only the pulse signal A reaches the communication device10. For this reason, as shown inFIG.5, the communication device10recognizes that a pulse signal with a pulse width z (x>y>w≠z) is received. Further, the reason why the pulse width shown inFIG.5is not the same as the pulse width w of the pulse signal at the time of transmission from the communication device20-3is that the pulse width changes slightly due to causes other than reflection (for example, signal attenuation) or the like.

As shown inFIGS.3to5, the pulse width of the pulse signal transmitted from the communication device20, which is closer to the communication device10, is recognized by the communication device10as a longer pulse width. The pulse width of the pulse signal transmitted from the communication device20-3farthest from the communication device10(i.e., disposed nearest the terminal end of the communication line30opposite to the communication device10) is recognized by the communication device10as the shortest pulse width.

From the above, the communication device10identifies the shortest pulse width of the plurality of measured pulse widths, and detects the communication device20that has transmitted the pulse signal with the specified pulse width as the communication device20disposed near the terminal end of the communication line30.

Hereinafter, a functional configuration of the communication device10will be described in more detail.

FIG.6is a block diagram showing a functional configuration of the communication device10according to the first embodiment. As shown inFIG.6, the communication device10is configured to include the terminating resistor11and a signal transmission/reception circuit12.

As shown inFIG.6, the terminating resistor11is always connected to the communication line30that is a two-line type communication line. Accordingly, the terminating resistor11makes the communication device10always function as a terminating device.

The signal transmission/reception circuit12is a main part as a detection device, and is a circuit configured to perform transmission and reception of the signal in communication between the communication devices20. The signal transmission/reception circuit12is a signal transmission/reception circuit included in the communication device10disposed nearest one terminal end of the communication line30as described above. In addition, the signal transmission/reception circuit12detects the communication device disposed near the other terminal end of the communication line30(hereinafter, referred to as “a terminal-end communication device”). The signal transmission/reception circuit12controls a setting state of the terminating resistor in each of the communication devices20by transmitting a command to each of the communication devices20.

As shown inFIG.6, the signal transmission/reception circuit12is configured to include a control unit120, a command unit121, a transmission unit122, a reception unit123, a measurement unit124, a storage unit125, a detection unit126, and a communication speed switching unit127.

The control unit120controls processing by each functional block provided in the signal transmission/reception circuit12. Accordingly, for example, the control unit120controls transmission and reception of the signal in communication between the communication devices20. In addition, for example, the control unit120controls processing of detecting the terminal-end communication device. In addition, for example, the control unit120controls transmission of various types of commands to the communication devices20.

The control unit120is a processor such as a central processing unit (CPU) or the like. Further, the control unit120may be realized using hardware such as a large-scale integrated circuit (LSI), an application specific integrated circuit (ASIC), or the like. In addition, each of the functional blocks provided in the signal transmission/reception circuit12may have a configuration realized by executing a program stored in the storage unit125using the control unit120that is a processor such as a CPU or the like.

The command unit121controls transmission of various types of commands transmitted to the communication devices20. The command unit121outputs various types of commands to the communication devices20via the transmission unit122. As shown inFIG.6, the command unit121includes a pulse signal output command unit121a, a terminating resistor setting command unit121b, and a communication speed switching command unit121c.

The pulse signal output command unit121aoutputs a pulse signal output command (a third command) indicating a command for outputting a pulse signal to the communication device10thereof to each of the communication devices20. Further, the pulse signal output command may be configured to be transmitted to each of the communication devices20through broadcasting or multicasting. Further, the signal output from each of the communication devices20according to the pulse signal output command is a test signal that is output experimentally, and is previously set to output a pulse with exactly the same time width in any of the communication devices20.

The terminating resistor setting command unit121boutputs a terminating resistor setting command (a first command) indicating a command for setting a terminating resistor to the terminal-end communication device when the terminal-end communication device is detected by the detection unit126.

Further, the terminating resistor setting command unit121bmay output a command for releasing the setting of the terminating resistor (a fourth command) to the terminal-end communication device when at least one communication device20is added or removed. After that, the signal transmission/reception circuit12may be configured to detect the terminal-end communication device again, and set the terminating resistor for the detected terminal-end communication device.

The communication speed switching command unit121cmay output a communication speed switching command (a second command) indicating a command for switching the communication setting such that a communication speed in communication with the communication device10thereof becomes higher (i.e., a command for switching the setting to a high speed communication mode) to the communication device20when the terminating resistor setting command is output by the terminating resistor setting command unit121b.

Further, the communication speed switching command unit121cmay output a command for switching the communication setting for decreasing the communication speed in communication with the communication device10thereof to be lower (i.e., a command for switching the setting to a low speed communication mode) (a fifth command) to each of the communication devices20connected to the communication line30when at least one of the communication devices20is added or removed. After that, the signal transmission/reception circuit12may be configured to detect the terminal-end communication device again, and set the terminating resistor for the detected terminal-end communication device.

The transmission unit122and the reception unit123are communication interfaces configured to be connected to the communication devices20through communication. Further, the transmission unit122and the reception unit123may be a functional unit constituted by one piece of hardware.

The transmission unit122outputs various signals (pulse signals) to the communication devices20via the communication line30under the control of the control unit120. Further, the various signals include the signals output from the command unit121and showing the pulse signal output command, the terminating resistor setting command, and the communication speed switching command, which are described above.

The reception unit123acquires various signals (pulse signals) output from the communication devices20via the communication line30. Further, the various signals also include a pulse signal that is a test signal output from each of the communication devices20according to acquisition of the pulse signal output command. The reception unit123outputs the acquired pulse signal to the measurement unit124when the pulse signal that is a test signal is acquired.

The measurement unit124acquires the pulse signal that is the test signal transmitted from each of the communication devices20from the reception unit123. The measurement unit124measures the pulse width of the acquired pulse signal. The measurement unit124stores the measurement value with the pulse width of the pulse signal transmitted from each of the communication devices20in the storage unit125. For example, the measurement unit124stores the previously stored measurement value in the storage unit125by writing the pulse width in the storage table t2, which will be described below.

The storage unit125stores various types of programs and theta tables used in the signal transmission/reception circuit12. The storage unit125is a non-volatile recording medium (a non-transient recording medium) such as a flash memory, a hard disk drive (HDD), or the like. In addition, the storage unit125may further have a volatile recording medium such as a random access memory (RAM), a register, or the like.

In addition, the storage unit125stores a communication device information table t1and a pulse width storage table t2, which will be described below.

FIG.7is a view showing an example of a configuration of the communication device information table t1stored in the communication device10according to the first embodiment. As shown inFIG.7, the communication device information table t1is data of a two-dimensional table form constituted by rows of two items of “identification number” and “address.” The value stored in the item of the identification number is an identification number for identifying each of the communication devices20. For example, it is shown that the identification numbers corresponding to the communication device20-1, the communication device20-2, and the communication device20-3are “c1,” “c2” and “c3” stored in the communication device information table t1shown inFIG.7.

In addition, the communication device information table t1is a table in which the identification numbers assigned to the communication devices20and the addresses required to cause the communication device10to perform communication with each of the communication devices20correspond to each other. For example, as shown inFIG.7, the address of the communication device20-1to which the identification number “c1” is assigned is expressed as “aaa.bbb.”

The communication device information table t1is a table that is previously stored in the storage unit125. The communication device10refers the address corresponding to the communication device20of a transmission destination using the communication device information table t1when the signal is transmitted to the specified communication device20. Then, the communication device10designates the referred address and transmits the signal. For example, as shown inFIG.7, the communication device10can transmit the signal to the communication device20-1to which the identification number “c1” is assigned by designating the address referred to as “aaa.bbb” and transmitting the signal.

FIG.8is a view showing an example of a configuration of the pulse width storage table t2stored in the communication device10according to the first embodiment. As shown inFIG.8, the pulse width storage table t2is data of a two-dimensional table format constituted by rows of two items of “identification number” and “pulse width.” The value stored in the item of the identification number is an identification number for identifying each of the communication devices20like the communication device information table t1.

The pulse width storage table t2is a table for temporarily storing pulse widths of pulse signals that are test signals output from the communication devices20. The pulse width storage table t2is in a state in which a value of an item of at least “pulse width” is not stored in the initial state. Whenever the pulse widths of the pulse signals output from the communication devices20are measured by the measurement unit124, data showing the measurement value is written in the pulse width storage table t2.

Accordingly, the pulse width storage table t2exemplified inFIG.8shows a state in which, while measurement of the pulse width of the pulse signal output from the communication device20-1to which the identification number “c1” is assigned and the pulse width of the pulse signal output from the communication device20-2to which the identification number “c2” is assigned are completed, measurement of the pulse width of the pulse signal output from the communication device20-3to which the identification number “c3” is assigned is not yet performed. Finally, measurement of the pulse widths from all the communication devices20is completed, and the pulse width storage table t2is filled.

The pulse width storage table t2exemplified inFIG.8shows that the measurement value of the pulse width of the pulse signal output from the communication device20-1to which the identification number “c1” is applied was “1.4” (a unit is ms (millisecond)).

Description will be performed again by returning toFIG.6.

The detection unit126refers the pulse width storage table t2stored in the storage unit125. The detection unit126identifies a value of the narrowest pulse width by referring a value stored in the item of “pulse width” of the pulse width storage table t2. Then, the detection unit126refers the value stored in the item of “identification accompaniment” of the pulse width storage table t2, and acquires the value of the identification number corresponding to the value of the narrowest pulse width. The detection unit126detects the communication device20to which the acquired identification number is assigned as the terminal-end communication device near the terminal end.

The detection unit126outputs the information showing the detected communication device20as the terminal-end communication device (for example, an identification number) to the terminating resistor setting command unit121b. The terminating resistor setting command unit121boutputs the terminating resistor setting command to the communication device20(the terminal-end communication device) based on the information acquired from the detection unit126.

When the terminating resistor setting command is output from the terminating resistor setting command unit121b, the communication speed switching command unit121coutputs a communication speed switching command to all the communication devices20. Accordingly, in the communication device20, the communication setting is switched to increase the communication speed in communication with the communication device10to be higher (i.e., switched to the high speed communication mode). Further, the communication speed switching command unit121cmay output the communication speed switching command to at least one communication device20.

The communication speed switching unit127switches the communication setting to increase the communication speed in communication with the communication device20to be higher (i.e., switching the setting to the high speed communication mode) when the terminating resistor setting command is output from the terminating resistor setting command unit121b). After that, the communication device10performs exchange of conventional information between the communication devices20in the high speed communication mode.

Further, the communication speed switching unit127may allow the terminal-end communication device to open the terminating resistor while switching the communication setting to decrease the communication speed in communication with the communication device20connected to the communication line30(i.e., switching the setting to a low speed communication mode) when at least one communication device20is added or removed. After that, the signal transmission/reception circuit12may be configured to detect the terminal-end communication device again, and set the terminating resistor for the detected terminal-end communication device. It is possible to improve stability of communication between the communication device10and the communication devices20and increase measurement accuracy of the pulse width in the measurement unit124using the low speed communication mode in searching of the terminal-end communication device.

Hereinafter, a configuration of the communication device20will be described.

FIG.9is a schematic diagram showing the configuration of the communication device20according to the first embodiment. Further, since the configurations of the communication devices20are the same as each other,FIG.9shows only the communication device20-2and the communication device20-3as an example. As shown inFIG.9, the communication device20is configured to include the terminating resistor setting unit21, and a signal transmission/reception circuit22.

The terminating resistor setting unit21is configured to include the terminating resistor. The terminating resistor setting unit21acquires the terminating resistor setting command transmitted from the communication device10. The terminating resistor setting unit21is switched to a state in which the terminating resistor is set when the terminating resistor setting command is acquired. Further,FIG.9shows a state in which the terminating resistor is switched to a setting state because the communication device20-3is the terminal-end communication device, and the terminating resistor is in a setting-released state because the communication device20-2is not the terminal-end communication device.

The signal transmission/reception circuit22is a circuit configured to perform transmission and reception of the signal in communication between the communication devices10. In addition, the signal transmission/reception circuit12acquires the pulse signal output command transmitted from the communication device10. The signal transmission/reception circuit12outputs the pulse signal with the prescribed pulse width w to the communication device10when the pulse signal output command is acquired.

In addition, the signal transmission/reception circuit12acquires the communication speed switching command transmitted from the communication device10. The signal transmission/reception circuit12switches the communication setting to increase the communication speed in communication with the communication device10to be higher (i.e., switching the setting to the high speed communication mode) when the communication speed switching command is acquired.

Hereinafter, an operation of the communication device10will be described.

FIG.10is a flowchart showing an example of an operation of the communication device10according to the first embodiment. For example, the operation of the communication device10shown inFIG.10is started in the initial state before the air-conditioning system100is operated.

First, the control unit120executes processing of substituting1for a variable i (step S001). Then, the control unit120executes processing from step S002to step S005, which will be described below, n times (i.e., three times in the case of the configuration shown inFIG.1) when the number of terminals connected to the communication device10is n.

The pulse signal output command unit121atransmits the pulse signal output command to the communication device20-i(i=1 to n) via the transmission unit122and the communication line30(step S002).

When the pulse signal transmitted from the communication device20-i(i=1 to n) according to the pulse signal output command transmitted in step S002is received by the reception unit123(in step S003, YES), the measurement unit124measures the pulse width of the received pulse signal (step S004). Meanwhile, when the pulse signal transmitted from the communication device20-i(i=1 to n) according to the pulse signal output command transmitted in step S002is not received (in step S003, NO), the communication device10waits until the pulse signal is received by the reception unit123.

The measurement unit124stores the value showing the measured pulse width in the storage unit125by writing the value in the pulse width storage table t2stored in the storage unit125(step S005).

The detection unit126refers the pulse width storage table t2stored in the storage unit125, and identifies the communication device20-jfrom which the pulse signal with the narrowest pulse width is output (i.e., in the case of the configuration shown inFIG.1, the communication device20-jis specified) (step S006).

The terminating resistor setting command unit121btransmits the terminating resistor setting command to the communication device20-jvia the transmission unit122and the communication line30(step S007).

The communication speed switching command unit121ctransmits the communication speed switching command to all the communication devices20via the transmission unit122and the communication line30(step S008).

The communication speed switching unit127switches the communication setting to increase the communication speed in communication with the communication device20to be higher (i.e., switching the setting to the high speed communication mode) (step S009).

An operation as the detection device in the communication device10shown by the flowchart ofFIG.10is terminated as described above.

Hereinafter, an operation of the communication device20will be described.

FIG.11is a flowchart showing an operation in pulse signal output processing of the communication device20according to the first embodiment. The operation of the communication device20shown inFIG.11is started when the pulse signal output command transmitted from the communication device10in step S002shown inFIG.10is received in the communication device20.

The signal transmission/reception circuit22receives the pulse signal output command transmitted from the communication device10via the communication line30(step S101).

The signal transmission/reception circuit22outputs the pulse signal with the prescribed pulse width (for example, the pulse width w) to the communication device10via the communication line30(step S102).

An operation of the communication device20shown by the flowchart ofFIG.11is terminated as described above.

FIG.12is a flowchart showing an operation in terminating resistor setting processing of the communication device20according to the first embodiment. The operation of the communication device20shown inFIG.12is started when the terminating resistor setting command transmitted from the communication device10in step S007shown inFIG.10is received in the communication device20.

The terminating resistor setting unit21acquires the terminating resistor setting command transmitted from the communication device10via the communication line30(step S111).

The terminating resistor setting unit21is switched to a state in which the terminating resistor is set (step S112).

The operation of the communication device20shown by the flowchart ofFIG.12is terminated as described above.

FIG.13is a flowchart showing an operation in communication speed switching processing of the communication device20according to the first embodiment. The operation of the communication device20shown inFIG.13is started when the communication speed switching command transmitted from the communication device10in step S008shown inFIG.10is received in the communication device20.

The signal transmission/reception circuit22receives the communication speed switching command transmitted from the communication device10via the communication line30(step S121).

The signal transmission/reception circuit22switches the communication setting to increase the communication speed in communication with the communication device10to be higher (i.e., switching the setting to the high speed communication mode) (step S122).

The operation of the communication device20shown by the flowchart ofFIG.13is terminated as described above.

Hereinafter, a configuration of an air-conditioning system200according to a variant of the first embodiment will be described.

FIG.14is the entire configuration view of the air-conditioning system200according to the variant of the first embodiment.

The configuration of the air-conditioning system200according to the variant of the first embodiment shown inFIG.14is distinguished from the configuration of the air-conditioning system100according to the first embodiment shown inFIG.10in that the communication line30is branched off in the middle, and the system includes an indoor unit2-4and an indoor unit2-5provided with a communication device20-4and a communication device20-5.

As shown inFIG.14, unlike the first embodiment, when the position of the communication line30on which the communication device10is installed is one terminal end, the other terminal end are present at two positions. That is, two terminal-end communication devices of the communication device20-3and the communication device20-5are present.

In this case, when the communication device10can previously discriminate the communication device20connected from the communication device10toward the communication device20-3along the communication line30and the communication device20connected from the communication device10toward the communication device20-5via the communication line30, the communication device10may divide the processing into two parts, the setting of the terminating resistor with respect to the communication line30from the communication device10toward the communication device20-3and the setting of the terminating resistor with respect to the communication line30from the communication device10toward the communication device20-5, and the processing according to the first embodiment may be executed respectively.

Meanwhile, even when the communication device10cannot discriminate the communication device20connected from the communication device10toward the communication device20-3along the communication line30and the communication device20connected from the communication device10toward the communication device20-5along the communication line30, the setting of the terminating resistor with respect to the communication device20-3and the communication device20-5is possible.

In this case, like the first embodiment, the communication device10acquires the pulse signals that are test signals from all the communication devices20, and measures the pulse widths, respectively. Then, the communication device10identifies the communication device20from which the pulse signal with the narrowest pulse width is output and the communication device20from which the pulse signal with the pulse width having a difference from the narrowest pulse width, which is smaller than a prescribed threshold, is output. Then, the communication device10is switched to a state in which the terminating resistor is set to the plurality of specified communication devices20.

InFIG.14, both of the communication device20-3and the communication device20-5are communication devices connected to the communication line30at positions of the terminal ends of the communication line30. Accordingly, as shown inFIG.5, no reflection occurs in any of the pulse signals transmitted from the communication device20-3and the communication device20-5. For this reason, basically, the pulse signals transmitted from the communication device20-3and the communication device20-5are recognized by the communication device10as any of the pulse signals with the pulse width z.

Further, as described above, the reason why the pulse width (z) shown inFIG.5is not the same as the pulse width w of the pulse signal at the time of transmission from the communication device20-3is that the pulse width is slightly varied due to a cause other than the reflection (for example, signal attenuation) or the like. For example, due to these changes, the pulse width of the pulse signal output from the communication device20-3and the pulse width of the pulse signal transmitted from the communication device20-5do not always exactly coincide with each other.

Second Embodiment

Hereinafter, a second embodiment will be described.

In the above-mentioned first embodiment, the communication device10is configured to acquire the pulse signals (the test signals) output from the communication devices20, and detect the communication device20, which has output the pulse signal acquired as the narrowest pulse width, as the terminal-end communication device.

Meanwhile, the communication device10according to the second embodiment acquires the pulse signals (the test signals) output from the communication devices20. Then, the communication device10according to the second embodiment includes an estimation unit (not shown) configured to estimate a length of the communication line30between the communication device10and each of the communication devices20on the basis of the measured pulse width. Further, the estimation method in this case is considered as, for example, a method of previously holding information in which the length of the communication line30between the communication device10and the communication device20corresponds to the pulse width received in the communication device10in the case of the length using the communication device10and performing estimation on the basis of the information.

According to the communication device10related to the second embodiment, an air-conditioning manager or the like can estimate the communication device20estimated to have the largest length of the communication line30using the estimation unit as the terminal-end communication device. Accordingly, the air-conditioning manager or the like can easily identify the terminal-end communication device, and set the terminating resistor with respect to the terminal-end communication device.

Hereinabove, while the embodiment has been described, in the above-mentioned embodiment, in order to simplify the description, only the signal reflection was targeted as a factor to change the signal waveform of the pulse signal. However, in actuality, the signal waveform changes according to the length of the communication line30and the number of intervening communication devices20, and the like. For example, as the length of the communication line30is increased, amplitude of the pulse signal may be attenuated depending on a resistance component, or a gradient may change due to a capacitance component or the like.

However, in any case, as the length of the communication line30is increased (i.e., the position of the communication device20is goes away from the communication device10, or the like), the waveform of the pulse signal is changed to narrow the pulse width. Accordingly, detection accuracy of the terminal-end communication device according to the embodiment is further increased.

Further, in the above-mentioned embodiment, while the used signal is the pulse signal constituted by values of 0 and 1, there is no limitation thereto. For example, even in the case of a signal for communication or the like pursuant to HBS Standard (home bus system: Electronic Industries Association of Japan (EIAJ) Standard, ET-2101), after converting to the pulse signal constituted by values of 0 and 1 as described above, the processing in the above-mentioned embodiment may be executed.

According to the at least one embodiment as described above, since the reception unit configured to receive the signals with the prescribed pulse widths transmitted from the plurality of communication devices20, the measurement unit configured to measure the pulse widths of the signals received by the reception unit, and the detection unit configured to detect the communication device disposed near the terminal end of the communication line30on the basis of the plurality of measured pulse widths are provided, it is possible to automatically detect the communication device20of the terminal end of the communication line30without human intervention. Accordingly, since the terminating resistor can be set to the communication device20of the terminal end of the communication line30, the communication between the communication device10and each of the communication devices20can be performed at a higher speed.

A part of or the entire communication device10according to the embodiment may be realized by a computer. In this case, the program configured to realize the function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be realized by being read and executed by a computer system. Further, “the computer system” disclosed herein includes an OS or hardware such as peripheral devices or the like. In addition, “the computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optic disk, an ROM, a CD-ROM, or the like, and a storage device such as a hard disk or the like built in the computer system. Further, “the computer-readable recording medium” may include a medium configured to dynamically hold a program for a short time, for example, a communication line when the program is transmitted via a network such as the Internet, a communication line such as a telephone line or the like, or a medium configured to temporarily hold a program, for example, a volatile memory in the computer system that becomes a server or a client in this case. In addition, the program may be configured to realize a part of the above-mentioned function, and the function may be further realized by combination with the program already stored in the computer system or may be realized using hardware such as a programmable logic device (PLD), a field programmable gate array (FPGA), or the like.

In the embodiment, while circuit parts for communication or control processing for communication are simplified by using both the communication device20configured to perform conventional communication and the detection device configured to set the terminating resistor to the communication device20of the terminal end, these two devices may be separated, and a detection device having a function of detecting the communication device20of the terminal end and setting the terminating resistor to the communication device20may be provided separately.

While some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the present invention. These embodiments may be implemented in various other forms, and various omissions, replacements, and changes may be made without departing from the spirit of the present invention. These embodiments and their variants are included in the scope and the spirit of the invention, as well as in the invention described in the claims and the equivalent scope thereof.

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