JP2002290490A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically recognize communication standards of the destination and carry out communication in compliance with the communication standards. SOLUTION: In an electronic device 1, a detection means 1a detects an interface specifications of an interface circuit 3a of a device 3 which carries out communication through a communication cable 2. A switching means 1b changes connections between the communication cable 2 and interface circuits 1d and 1e according to the interface specifications detected by the detection device 1a. At this time, the switching means 1b switches to the interface circuit 1d or 1e which complies with the communication standards of the device 3. The selecting means 1c changes over communication protocol of a software level in compliance with the communication standards of the device 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device, and more particularly, to an electronic device that performs communication by connecting a communication cable.

[0002]

2. Description of the Related Art Various interface specifications are introduced to peripheral devices connected to a PC (personal computer) as technology advances. Therefore, it is necessary to match the specifications of the interface between the PC and the peripheral device.

In order to cope with a plurality of communication standards with a single electronic device, a circuit corresponding to each communication standard is mounted, and a circuit conforming to the communication standard and a communication cable are appropriately connected by a jumper wire or the like. There is. For example, Japanese Unexamined Patent Publication
There is an electronic device as disclosed in JP-A-90305.

[0004] Further, among electronic devices to which a power supply voltage is externally supplied via a communication cable, there are electronic devices that use the polarity of the supplied power supply voltage. For example, a certain communication standard uses a cable in which the polarity of the power supply voltage is not inverted, and a certain communication standard uses a cable in which the polarity is inverted. The electronic device detects the voltage polarity sent from the cable, selects a circuit of a communication standard corresponding to the device to be connected, and switches the connection according to the result.

[0005]

As described above, in order to perform communication in accordance with a plurality of communication standards with one electronic device, a circuit corresponding to each communication standard is mounted, and a communication standard used as appropriate is used. The corresponding circuit must be manually switched, which is complicated.

Further, in order to detect the polarity of the power supply voltage sent via the communication cable and determine the communication standard, a plurality of dedicated cables must be prepared, resulting in erroneous connection of the cables.

[0007] The present invention has been made in view of the above points, and it is an object of the present invention to provide an electronic apparatus which can automatically cope with an interface of a device to which a communication cable is connected.

Another object of the present invention is to provide an electronic apparatus which can cope with an interface of a connection destination device with a single cable.

[0009]

According to the present invention, in order to solve the above-mentioned problems, in an electronic device which can be connected to an interface having a different specification, a detecting means for detecting an interface of a device to be connected, and an interface corresponding to the interface An electronic apparatus is provided, comprising: a circuit; and switching means for switching connection to the interface circuit in accordance with the specification of the interface detected by the detection means.

According to such an electronic device, by connecting to another device with a communication cable, communication is automatically switched to the communication standard of the connected device and communication is performed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram illustrating the operation principle of the electronic device of the present invention. As shown in this figure, the electronic device 1 of the present invention includes a detecting unit 1a, a switching unit 1b, a selecting unit 1c, and interface circuits 1d and 1e. The communication cable 2 includes a communication line for transmitting various electric signals between the electronic device 1 and the device 3. Device 3
Is composed of an interface circuit 3a.

The detecting means 1a detects the specifications of the interface of the device 3 to be connected. The switching means 1b is connected to the communication cable 2 and the interface circuits 1d, 1d in accordance with the specification of the interface of the connection destination detected by the detection means 1a.
Switch the connection with e.

The selecting means 1c is equipped with a communication protocol at the software level, and selects and executes a communication protocol conforming to the interface of the device 3 to be connected.
The interface circuits 1d, 1e, and 3a satisfy electrical communication standards and transmit and receive signals between the electronic device 1 and the device 3.

The communication cable 2 transmits various signals of the electronic device 1 and the device 3, and is connected to the detecting means 1a and the switching means 1b. Next, the operation of the above principle diagram will be described.

Now, it is assumed that the electronic device 1 and the device 3 are connected by the communication cable 2. At this time, the detecting means 1a detects the specifications of the interface of the device 3.
Therefore, the switching unit 1b switches the connection between the communication cable 2 and the interface circuit 1d or the interface circuit 1e according to the detected interface specification. At this time, it is connected to an interface circuit conforming to the communication standard of the device 3. The selecting means 1c selects and executes a protocol conforming to each communication standard at the software level in accordance with the detected interface specification.

In the above electronic device 1, the number of interface circuits is two, but may be more.
As described above, the electronic device 1 detects the interface specification of the device 3 by the detection unit 1a, and the switching unit 1b sets the interface cable 1d or the interface circuit 1e and the communication cable 2e corresponding to the detected interface specification. And the selecting means 1c selects a communication protocol at the software level, so that communication can be automatically performed with a device using any communication standard.

Next, an example of an embodiment of the present invention will be described. FIG. 2 is a circuit diagram showing a case where a USB standard device is connected to the electronic apparatus of the present invention, and FIG. 3 is a circuit diagram of a detection voltage at the time of USB connection.

An electronic device 10 according to the present invention shown in FIG. 2 is a communication interface portion of a digital camera connected to, for example, a PC, and includes a control device 11, an interface circuit 12a,
12b, switches SW1, SW2, SW3, and a resistor R
1, R2, R3, R4 and a voltage source VCC. The communication cable 20 includes the electronic device 10 and the device 3
It is composed of communication lines for transmitting various electric signals between 0, and signal lines 21 and 22 therein are shown in the figure. The device 30 includes resistors R5 and R6 and an interface circuit 31, and is, for example, an interface portion of a PC that communicates with a digital camera.

The control device 11 has an analog-to-digital converter and a terminal A / D which is an input terminal of an analog signal.
It has an input and converts a voltage input to a terminal A / D input into a digital signal. The control device 11 has terminals CONT1, CONT2, and CONT3 that output control signals, and changes the state of the voltage “H” or “L” according to the value of the digital signal of the voltage input to the terminal A / D input. Output. Although not shown in the figure, the USB standard, RS-232
Equipped with a software protocol that conforms to the standard.

The interface circuits 12a and 12b transmit and receive signals. The interface circuit 12a is a US
B, and the interface circuit 12b
Meets the RS-232 communication standard. Here, the USB standard has two types of categories, a high-speed device and a low-speed device, but it is assumed that a high-speed device is used.

The switches SW1, SW2, and SW3 are constituted by semiconductor switches and the like. Switch SW1,
SW2 and SW3 are terminals CONT1, CONT2, CO
ON when the voltage applied from NT3 is "H",
In the state of “L”, the state is OFF.

The resistor R1 supplies a voltage to the signal line 21 and has a resistance of 15 kΩ. The resistors R2 and R3 function as pull-down resistors. The resistor R4 is connected between the voltage source VCC and the signal line 21 to use a USB standard high-speed device, and has a resistance of 1.5 kΩ.

The voltage of the voltage source VCC is set to 3.3V. The device 30 has a USB standard interface circuit 31 mounted thereon. The interface circuit 31 has terminals D + and D- for transmitting and receiving signals. The resistors R5 and R6 are resistors defined by the USB standard, are connected between the terminal D + and the ground and between the terminal D- and the ground, and each have a resistance of 15 kΩ.

The communication cable 20 is connected to terminals D + and D- of the interface circuit 31 and switches SW1, SW2 and SW.
3 are connected by signal lines 21 and 22. The circuit of FIG.
1, R5. When the switch SW1 is ON, the resistors R1 and R5 are connected in series between the voltage source VCC and the ground. The connection point between the resistors R1 and R5 is connected to a terminal A / D input of the control device 11.

Hereinafter, the operation of the circuit diagram of FIG. 2 will be described. First, the control device 11 sets the terminals CONT2 and CONT3 to the “L” state and turns off the switches SW2 and SW3 at the same time when the power of the electronic device 10 is turned on. Even before the control device 11 starts operating, the terminals CONT2 and CONT3 have the resistance R
2, since it is connected to the ground via R3, it is in the "L" state.

Subsequently, the terminal CONT1 is set to the "H" state,
The switch SW1 is turned on. At this time, the electronic device 10
However, when it is not connected to the device 30 via the communication cable 20, the voltage of the terminal A / D input is 3.3V.
If connected, the input terminal of the A / D converter has a high input impedance, and the connection relationship between the resistors R1 and R5 is as shown in FIG. For this reason, the voltage of the terminal A / D input is obtained by connecting the voltage between the voltage source VCC and the ground to the resistor R1,
It becomes a value divided by R5 and becomes 1.65V.

The control device 11 converts the voltage input from the terminal A / D input into a digital signal. If the voltage is 3.3 V, the device 30 is not connected. If the voltage is 1.65 V, the device 30 conforms to the USB standard.
Is determined to be connected. At this time, a communication protocol conforming to the USB standard at the software level is selected and executed.

If it is determined that the USB standard device 30 is connected, the control device 11 sets the terminal CONT1 to the "L" state and turns off the switch SW1. Subsequently, the control device 11 sets the terminal CONT2 to the “H” state and sets the switch S
Turn W2 ON. Thus, the communication line of the communication cable 20 is connected to the interface circuit 12a, and the device 3
Communicates with 0.

With the above operation, the electronic device 10 automatically switches to the USB communication standard of the device 30. Further, even when a device having a communication standard not provided in the electronic device 10 is connected, the switches SW2 and SW3 are turned off when the power is turned on.
Interface circuit 12 of the electronic device 10
a, 12b is prevented from being damaged. In addition, since the switch SW1 is turned off after the device 30 is determined, the resistor R1 does not load the terminal D + of the interface circuit 31.

FIG. 4 is a block diagram showing an electronic device according to the present invention.
FIG. 5 is a circuit diagram showing a case where a standard device is connected, and FIG.
It is a circuit diagram of the detection voltage at the time of S-232 connection. The electronic device 10 has the same configuration as the electronic device 10 in FIG. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The device 40 is, for example, a PC, and is an interface circuit 4 of the RS-232 standard for communicating with a digital camera.
1 is mounted. The interface circuit 41 has terminals RxD and TxD for transmitting and receiving signals. Also, RS-2
According to the 32 standard, the input impedance of the terminal RxD is 3
It is specified as k to 7 kΩ.

The communication cable 20 connects the terminals RxD, TxD of the interface circuit 41 and the switches SW1, SW2, SW3 with signal lines 21, 22. The circuit diagram of FIG.
1. An interface circuit 41 is provided. The terminal RxD of the interface circuit 41 has an input impedance Z
One. The terminal TxD is omitted. When the switch SW1 is ON, the resistor R1 and the input impedance Z1 are connected in series between the voltage source VCC and the ground. The resistance R
1 and the input impedance Z1 are connected to the terminal A / D input of the control device 11.

Hereinafter, the operation of the circuit diagram of FIG. 4 will be described. First, the control device 11 sets the terminals CONT2 and CONT3 to the “L” state and turns off the switches SW2 and SW3. Next, the terminal CONT1 is set to the “H” state, and the switch SW1 is turned on.

At this time, when the electronic device 10 is not connected to the device 40 via the communication cable 20, the terminal A
The voltage at the / D input is 3.3V. When connected, since the input terminal of the A / D converter has a high input impedance, the connection relationship between the resistor R1 and the input impedance Z1 is as shown in FIG. The voltage of the terminal A / D input is obtained by connecting the voltage between the voltage source VCC and the ground to the resistor R1 and the terminal RxD.
Is a value divided by the input impedance Z1 (3 k to 7 kΩ), which is 0.55 to 1.05 V.

The control device 11 converts the voltage input from the terminal A / D input into a digital signal. If the voltage is 3.3 V, the device 40 is not connected.
It is determined that the two-standard device 40 is connected. At this time,
A communication protocol conforming to the RS-232 standard at the software level is selected and executed.

When it is determined that the RS-232 standard device 40 is connected, the control device 11 sets the terminal CONT1 to the "L" state, and turns off the switch SW1. Subsequently, the control device 11 sets the terminal CONT3 to the “H” state and turns on the switch SW3. Thus, the communication line of the communication cable 20 is connected to the interface circuit 12b, and communicates with the device 40.

With the above operation, the electronic device 10 automatically switches to the RS-232 communication standard of the device 40. Further, even when a device having a communication standard not provided in the electronic device 10 is connected, the switches SW2, SW
Since 3 is turned off, the interface circuits 12a and 12b of the electronic device 10 are prevented from being damaged. After the device 40 is determined, the switch R1 is turned off.
Does not load the terminal RxD of the interface circuit 41.

FIG. 6 is a diagram showing the relationship between the connected device and the voltage of the terminal A / D input. Electronic equipment 10 and device 3
The voltage of the terminal A / D input when 0 and 40 are not connected is 3.
3V.

The terminal A / when the device 30 is connected
The voltage at the D input is 1.65V. When the device 40 is connected, the voltage of the terminal A / D input is 0.55 to 1.0.
5V.

As described above, the difference in impedance can be detected as a voltage. Based on the difference in the value, it is determined whether or not there is a connection, and whether or not a USB standard or RS-232 standard device is connected. In the control device 11, the terminal A
If the voltage at the / D input is less than 1.3V, connect the device 40;
If the voltage is 1.3 V or more and less than 2.0 V, connect the device 30;
If it is 2.0 V or more, it is possible to determine that the connection is not established by setting a threshold value.

FIG. 7 shows an operation procedure of the control device. When the electronic device 10 is turned on (S61), the control device 11
Sets the terminals CONT2 and CONT3 to the “L” state (S
62), switches SW2 and SW3 are turned off.

Subsequently, the control device 11 sets the terminal CONT1 to "H" (S63), and turns on the switch SW1. Therefore, the control device 11 detects the voltage of the terminal A / D input as a digital signal (S64), and determines the communication standard of the device based on the detected voltage value. If the voltage is less than 1.3 V, the terminal CONT1 is set to the "L" state (S65), and the switch SW1 is turned off.

Subsequently, the control device 11 sets the terminal CONT3 to the "H" state (S66), turns on the switch SW3, and terminates (S69). On the other hand, when the voltage of the terminal A / D input is 1.3 V or more and less than 2.0 V, the control device 11
The terminal CONT1 is set to the “L” state (S67), and the switch SW1 is turned off.

Subsequently, the controller 11 sets the CONT2 to the "H" state (S68), turns on the switch SW2, and terminates (S69). On the other hand, when the voltage of the terminal A / D input is 2.0 V or more, the voltage of the terminal A / D input is detected (S64).

As described above, when the voltage of the terminal A / D input is 1.
If less than 3 V (S65): RS-232 standard device 40
Connection, 1.3V or more and less than 2.0V (S67)
USB device 30 connection, 2.0 V or more (S
64) It can also be determined by setting a threshold value as not connected.

When the control device 11 determines the communication standard based on the voltage of the terminal A / D input (S64), it selects and executes a protocol conforming to each communication standard at the software level.

Although the present invention is a digital camera for an example of the embodiment of the present invention, the present invention may be other peripheral devices of a PC, for example, a keyboard of the PC, but is not limited to these.

Although the voltage source VCC is set to 3.3 V and the resistor R1 is set to 15 kΩ, the values are not limited to these values. Further, the electronic device 10 has only an interface circuit that satisfies the communication standards of USB and RS-232, but a single electronic device can further support a plurality of communication standards by mounting an interface circuit of another standard. It becomes possible.

Although the description has been made using two interface circuits, three or more interface circuits may be mounted. Further, the threshold value is not limited to the value described above.

As described above, the communication standard of another device is automatically recognized, a plurality of communication standards can be supported, and connection can be easily performed. In addition, since communication with a plurality of devices becomes possible, restrictions on devices to be connected are reduced.

Also, for example, using two connectors,
Compared to the case of supporting various types of communication standards, only one connector is required, so that the device size and cost can be reduced.

Further, it is possible to develop a product corresponding to several kinds of communication specifications while maintaining upward compatibility with existing equipment by adding only a few circuits. Therefore, the development cost can be reduced and the development speed can be reduced.

Further, since the number of pins of the connector can be minimized, the size of the connector can be reduced. As a result, the size of the electronic device and the size of the cable can be reduced, and the cost can be reduced.

[0054]

As described above, according to the present invention, since the interface of the connected device is detected and the connection of the interface circuit is switched, the communication with the connected device can be performed without manually connecting to the corresponding interface circuit. It can be performed.

Further, communication can be performed without requiring a special communication cable.

[Brief description of the drawings]

FIG. 1 is a principle diagram illustrating an operation principle of an electronic device of the present invention.

FIG. 2 is a circuit diagram illustrating a case where a USB standard device is connected to the electronic apparatus.

FIG. 3 is a circuit diagram of a detection voltage at the time of USB connection.

FIG. 4 is a circuit diagram showing a case where an RS-232 standard device is connected to the electronic apparatus.

FIG. 5 is a circuit diagram of a detection voltage when RS-232 is connected.

FIG. 6 is a diagram illustrating a relationship between a connected device and a voltage of a terminal A / D input.

FIG. 7 is a diagram showing an operation procedure of the control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic equipment, 1a ... Detection means, 1b ... Switching means, 1
c: selection means, 1d, 1e: interface circuit, 2 ...
Communication cable, 3 ... device, 3a ... interface, 10
... Electronic equipment, 11 ... Control device, 12a, 12b ... Interface circuit, 20 ... Communication cable, 21, 22 ... Signal line, 30 ... Device, 31 ... Interface circuit, 40 ... Device, 41 ... Interface circuit

Claims (4)

[Claims] 1. An electronic device which can be connected to an interface having a different specification, a detection unit for detecting an interface of a device to be connected, an interface circuit corresponding to the interface, and a specification for the interface detected by the detection unit. Switching means for switching connection with the interface circuit; a communication protocol corresponding to the interface circuit; and a selection means for selecting the communication protocol in accordance with the specification of the interface detected by the detection means. An electronic device comprising: 2. The apparatus according to claim 1, wherein said detecting means is connected to a device to be connected by a communication cable, and has impedance detecting means for detecting an impedance between a signal line and a ground line of said communication cable. Electronic device as described. 3. The impedance detection unit includes: a voltage supply unit that applies a voltage from a voltage source via a resistor to the signal line; and a digital signal that changes a voltage of the signal line according to an impedance value of the signal line. The electronic device according to claim 2, further comprising: a control device configured to convert the data into: 4. The electronic device according to claim 1, wherein one of the interfaces is a USB communication standard and the other is an RS-232 communication standard.