JP2001144772A - Usb device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect physical disconnection of a host side computer and a USB device having a self power source when it is disconnected. SOLUTION: The USB device 1 is connected to the host side computer 2 by a USB cable 6 having signal lines 3 and 4, a power source line 5 and a grounded line 20, communicating with the computer 2 with its own power source 7. In the device 1, a voltage detecting part 10 for detecting a power source voltage supplied from the computer 2 is connected to a power source line connecting Vbus terminal 9 which is arranged in a connector 8 at the side of the device 1 to which the USB cable 6 is connected. The connection of the USB cable 6 is detected by the output of the voltage detecting part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a USB connected to a host computer by using a USB cable.
About the device. More specifically, the present invention relates to a USB device having a so-called self-power supply.

[0002]

2. Description of the Related Art There is a universal serial bus standard (hereinafter referred to as USB) as an interface for connecting a host computer such as a personal computer and peripheral devices. Connect U to the USB terminal of the host computer.
When a USB device such as a mouse or keyboard is connected via the SB cable, the host computer
The electrical change of the B interface is detected to recognize that the USB device is connected. The host-side computer performs electrical communication (hereinafter referred to as USB communication) to the connected USB device, recognizes the type of the USB device in response to the USB device, incorporates a corresponding USB device driver, and can control the USB device. State. This makes it possible to realize a so-called plug-and-play system that can be used only by connecting a USB device to a host computer via a USB cable.

[0003] USB communication is performed using two lines, a D + signal line and a D- signal line. Also,
A power supply line and a ground line are provided to enable power to be supplied from the host computer. That is, US
The B cable and USB terminal have these four types of lines.

There are two types of power supply methods for USB devices. One is to supply power from a USB terminal of a host-side computer via a power line of a USB cable (hereinafter, referred to as bus-powered).
One is that the USB device itself has a power supply (hereinafter, referred to as self-powered). This self-powered U
In an SB device, that is, a USB device having a so-called self-power supply, the USB device itself uses, for example, a commercial power supply, and does not require power supply from a host computer.

However, no matter which power supply method is used, the USB device cannot detect the connection state of the USB cable. However, the power supply of the bus-powered USB device is cut off when the connection state of the USB cable is canceled (for example, when the USB cable is disconnected), and the operation stops at that point.
In other words, even if the connection state of the USB cable cannot be detected, the operation is stopped if the connection state is resolved, so that it is unnecessary to detect the connection state.

[0006]

However, in the above-described USB device having a self-power supply, even if the connection state of the USB cable is canceled, the power supply continues, so that the operation continues. If the connection state of the USB cable can be detected, measures to stop the operation can be taken.
Since the connection state of the USB cable cannot be detected on the B device side, no means can be taken.

As described above, in the case of self-powered operation, it operates independently even when the connection with the host computer is cut off. That is, the operation continues even though the USB device is not under the control of the host computer.

[0008] Further, such inconveniences may occur even when the USB cable is not disconnected, such as a poor connection of the USB connector or a U-connection.
Like the disconnection of the SB cable, it may occur when the connection between the host computer and the USB device is physically disconnected.

Accordingly, an object of the present invention is to provide a USB device capable of detecting when a connection between a host-side computer and a USB device having its own power supply is physically disconnected.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a host computer is provided with:
A USB device configured to communicate with a host-side computer by being connected by a USB cable having a signal line and a power supply line, and having a self-power supply, the USB device being connected to the USB cable A voltage detection unit for detecting a power supply voltage supplied from the host computer is connected to a power line connection terminal provided in the connector unit on the side, and the connection of the USB cable can be detected by the output of the voltage detection unit. Like that.

Therefore, the output of the voltage detection unit is
USB cable connection can be detected.
When the cable is disconnected from the host computer or the connector of the USB device and the connection between them is disconnected, the disconnection can be detected and the USB device can be stopped.

According to a second aspect of the present invention, in the USB device according to the first aspect, the USB cable is a D +
A signal line comprising a signal line and a D-signal line;
A power supply line and a ground line are provided, and the connector portion on the USB device side is provided with connection terminals corresponding to each line.

Therefore, USB communication can be performed using two signal lines, the D + signal line and the D- signal line.

Further, the invention described in claim 3 is the invention according to claim 1.
Or in the USB device described in 2, the USB device operates by its own power supply,
The voltage detection unit provided in the device outputs the presence or absence of the specified voltage to the control unit in the USB device, and stops the operation of the USB device when detecting disconnection of the USB cable.

Therefore, when the disconnection of the USB cable is detected, the operation of the USB device can be stopped.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an example of an embodiment shown in the drawings. FIG. 1 shows an embodiment of the USB device 1 of the present invention. This US
The B device 1 is connected to the host computer 2 via a USB cable 6 having signal lines 3 and 4, a power supply line 5, and a ground line 20, and is configured to communicate with the host computer 2.

The USB cable 6 has a slight difference in configuration between a low-speed device and a high-speed device (for example, a high-speed device requires a shielded wire, but a low-speed device does not require a shield wire). Signal lines 3 and 4, power supply line 5 and ground line 20
Is always prepared. Therefore, in the present embodiment, the signal lines 3 and 4, the power supply line 5, and the ground line 20 provided for both the low-speed device and the high-speed device are illustrated, and are referred to as USB cables 6.

The USB device 1 has its own power supply 7. Furthermore, in this USB device 1, US
A voltage detection unit 10 for detecting a power supply voltage (Vbus) supplied from the host computer 2 to a power supply line connection Vbus terminal 9 provided in the connector unit 8 of the USB device 1 to which the B cable 6 is connected. Are connected. Thus, the connection of the USB cable 6 can be detected by the output of the voltage detection unit 10.

The voltage detector 10 provided in the USB device 1 outputs the presence or absence of a specified voltage to the CPU 11 which is a control unit in the USB device 1.
The presence or absence of the specified voltage here is output, for example, as an H or L signal. When the voltage detector 10 outputs to the CPU 11 that there is no specified voltage, the CPU 11 determines that the connection of the USB cable 6 has been physically disconnected, and
The operation of the B device 1 is stopped. Therefore, it is possible to prevent the USB device 1 from continuing to operate when the USB cable 6 is disconnected from the host computer 2 or the USB device 1, and prevent the USB device 1 from operating outside the control of the host computer 2. it can.

Not only when the USB cable 6 is unplugged, but also when the USB cable 6 and each of the USB connector portions 8, 1
The USB device 1 operates outside the control of the host computer 2 when the connection between the host computer 2 and the Vbus of the USB device 1 is physically disconnected due to poor contact with the USB cable 5, disconnection of the USB cable 6, or the like. It can be prevented from continuing.

The voltage detecting unit 10 utilizes a voltage detecting IC. In the present embodiment, an IC for voltage detection is adopted as the voltage detection unit 10. However, the voltage detection unit 10 is not limited to this, and may have a discrete configuration using transistors or FETs or a configuration using a comparator. .
Alternatively, the determination may be made by the CPU 11 using an AD converter (either external or internal to the CPU is possible). Thus, a known or new voltage detecting means can be used. In addition, the self power source 7 has an AC of 100.
It can be supplied from a volt commercial power supply, or can use a battery.

The connector section 8 of the USB device 1
It has a Vbus terminal 9 for power supply line connection, two signal line terminals 12 and 13, and a ground line terminal 14. The signal line terminals 12 and 13 include a D + signal line terminal 12 and a D− signal line terminal 13. On the other hand, the USB connector 15 of the host-side computer 2 has the same Vb as the connector 8 of the USB device 1.
It has a power line terminal 16 for outputting us, a D + signal line terminal 17, a D- signal line terminal 18, and a ground line terminal 19. In addition, these USB
US connecting device 1 and host-side computer 2
The B cable 6 has a power line 5 and a D + signal line 3
, A D-signal line 4, and a ground line 20, and connect the corresponding terminals of the USB device 1 and the host computer 2 to each other.

In this embodiment, the USB device 1 is used for either low speed or high speed. Although not particularly shown, when a low-speed device is used, a low-speed U
Using the SB cable 6 and the D of the USB device 1
Pull up to 3.3V line using 1.5 kOhm ± 5% resistor inside USB device 1 for signal line 4 In the case of a high-speed device,
A high-speed USB cable 6 is used, and the D + signal line 3 of the USB device 1 is pulled up to a 3.3 V line by using a resistance of 1.5 kΩ ± 5% inside the USB device 1. In each case, U is determined using both the D + signal line 3 and the D− signal line 4.
Perform SB communication.

The operation of the USB device 1 will be described with reference to the flowchart shown in FIG. The USB device 1 including the CPU 11 operates by the power supplied from the self-power supply 7. The CPU 11 of the USB device 1 executes a connection confirmation routine of the USB cable 6 as needed (for example, at regular intervals) (step 1). CPU1
1 determines the presence or absence of the power supply voltage (Vbus) supplied from the host computer 2 based on the output of the voltage detection unit 10 (step 2). If the CPU 11 determines that there is a Vbus (step 2; YES), it determines that the USB cable 6 is connected, ends the connection confirmation routine, and
Is continued (step 3).

The CPU 11 uses the output of the voltage
Is determined (step 2). If the CPU 11 determines that there is no Vbus (step 2; NO), the operation of the USB device 1 is stopped assuming that the connection of the USB cable 6 has been physically disconnected for some reason (step 4). This prevents the USB device 1 from continuing to operate outside of the control of the host computer 2 when the connection of the USB cable 6 is disconnected.

Also, by notifying the user that the USB connection has been disconnected in step 4 by means of a display, sound or communication, it is possible to artificially restore the USB connection or to discover an artificial failure. It is considered convenient.

Then, the CPU 11 determines again whether or not there is a Vbus based on the output of the voltage detector 10 as necessary (step 5). If the CPU 11 determines that there is no Vbus (step 5; NO), the operation stop state is maintained. On the other hand, CPU1
If 1 judges that Vbus is present (step 5; YES), U
It is determined that the SB cable 6 has been reconnected, and the operation of the USB device 1 is restarted or started from initialization (step 6).

According to the USB device 1, the connection of the USB cable 6 can be confirmed at the time of the initial operation. That is, when the USB device 1 is energized (power is turned on), the initialization operation of the CPU 11 is started, and preparation for USB communication on the USB device 1 side is completed, the connection of the USB cable 6 is confirmed. To do. Here, if it is determined that the USB cable 6 is connected, the processing shifts to communication processing for plug and play. On the other hand, if it is determined that the USB cable 6 is not connected, the process waits until the USB cable 6 is connected.

The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the USB cable 6 includes two signal lines 3 and 4, a power supply line 5, and a ground line 20 provided for both a low-speed device and a high-speed device so as to conform to the current USB standard. However, the present invention is not limited to this, and the lines constituting the USB cable 6 may be changed when the USB standard is changed. Also in this case, since the disconnection of the power supply line 5 can be detected by the output of the voltage detection unit 10, the USB device 1 can be stopped by detecting this disconnection.

[0030]

As is clear from the above description, according to the USB device of the first aspect, the connection of the USB cable can be detected by the output of the voltage detection unit, so that the USB cable can be connected to the host computer or the host computer. U
When the connection between the two devices is disconnected due to disconnection from the connector portion of the SB device or the like, the disconnection can be detected and the USB device can be stopped.

According to the USB device of the second aspect, USB communication can be performed using two signal lines of the D + signal line and the D- signal line.

Further, according to the USB device of the third aspect, when the disconnection of the USB cable is detected, the operation of the USB device can be stopped.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a USB device of the present invention.

FIG. 2 is a flowchart illustrating an operation procedure of a CPU of the USB device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 USB device 2 Host side computer 3 D + signal line (signal line) 4 D- signal line (signal line) 5 Power supply line 6 USB cable 7 Self-power supply 8 USB device side connector part 9 Vbus terminal 10 Voltage detection part 20 Ground line

Claims (3)

[Claims] 1. A USB device connected to a host-side computer by a USB cable having a signal line and a power supply line to communicate with the host-side computer, and configured to have its own power supply In the above, a voltage detection unit for detecting a power supply voltage supplied from the host-side computer is connected to the power line connection terminal provided in the USB device-side connector unit to which the USB cable is connected. A USB device, wherein the connection of the USB cable can be detected based on an output of the voltage detection unit. 2. The USB cable includes: the signal line including a D + signal line and a D− signal line; the power supply line; and a ground line. 2. The USB device according to claim 1, further comprising a connection terminal corresponding to said line. 3. The USB device is operated by the self-power supply, and the voltage detection unit provided in the USB device determines whether or not a specified voltage exists in the USB device.
2. The device according to claim 1, wherein an output is output to a control unit in the B device, and when the disconnection of the USB cable is detected, the operation of the USB device is stopped.
Or the USB device according to 2.