JP4444219B2 - Communications system - Google Patents

Description

The present invention relates to a communication system, and in particular, when a communication between a host device and a device device via a bus is started or resumed (recovered), the host device performs an initialization process on the device device. The present invention relates to a suitable communication system .

  FIG. 3 shows a communication system 1 in which a host apparatus 2 and a device apparatus 3 are connected via a USB bus as an application example of a general USB (Universal Serial Bus) conventionally employed.

  As shown in FIG. 3, the host device 2 includes a host-side USB controller 5 that performs various controls and processes for communication with the device device 3 via USB.

  In addition, the device apparatus 3 includes a device-side USB controller 6 that performs various processes, control, and processing for communication with the host apparatus 2 via the USB on the device apparatus 3 side.

  The host-side USB controller 5 and the device-side USB controller 6 are connected by a power supply line 8 as a USB bus and two differential type data signal lines 9 and 10 (D + and D−).

  In FIG. 3, the ground line as the USB bus is omitted. Further, a portion between the host device 2 and the device device 3 in each USB bus 8, 9, 10 is formed as a USB cable 12 so as to be detachable from both the devices 2, 3.

  When the device device 6 is connected via the USB cable 12, the host device 2 supplies power to the device device 3 from the power supply terminal VBUS via the power supply line 8 under the control of the host-side USB controller 5. It has become.

  The power supplied to the device apparatus 3 is input to the device-side USB controller 6.

  When power is supplied to the device device 3 by the host device 2, the voltage level of the power supply line 8 detected by the host-side USB controller 5 of the host device 2 is as shown in (1) of FIG. , A high level (High) (+5 V in (1) of FIG. 4).

  FIG. 3 schematically shows that a + 5V DC power supply 14 is supplied from the host apparatus 2 to the device apparatus 3 as a power supply.

  When the power supply 14 is supplied from the host apparatus 2 to the device apparatus 3, the voltage level of the power supply on the device side is changed from a low level (Low) (0V) to a high level (High) as shown in (2) of FIG. It rises to (+ 5V).

  The device-side USB controller 6 converts the power supply 14 supplied from the host apparatus 2 side into a pull-up power supply having a voltage lower than the voltage of the power supply 14 (for example, +3 V) and holds it.

  A pull-up resistor 16 having a predetermined resistance value (1.5 kΩ in FIG. 3) is connected between the terminal portion 15 of the pull-up power supply in the device-side USB controller 6 and the plus-side data signal line 9.

  Further, a positive pull-down resistor having a resistance value (15 kΩ in FIG. 3) higher than that of the pull-up resistor 16 between the D + data signal line 9 (hereinafter referred to as a positive data signal line 9) and the ground GND. 17 is connected. Further, a negative pull-down resistor 18 having the same resistance value as that of the positive pull-down resistor 17 is connected between the D- data signal line 10 (hereinafter referred to as the negative data signal line 10) and the ground GND. Yes.

  Here, when the power supply 14 is supplied from the host device 2 to the device device 3, pull-up is performed in which the plus-side data signal line 9 is connected to the pull-up power supply via the pull-up resistor 16.

  As a result of this pull-up, as shown in FIG. 4 (3), the voltage level of the plus-side data signal line 9 detected by the host-side USB controller 5 of the host device 2 becomes low (ground level: 0 V). ) To a higher level (+ 3V).

  As a result, the host apparatus 2 can recognize that the device apparatus 3 is connected, and can execute initialization processing such as enumeration on the device apparatus 3 under the control of the host-side USB controller 5.

  This initialization process is known as an indispensable process when communication is started between the host apparatus 2 and the device apparatus 3 or when communication is once interrupted and this initialization process is performed. If it is not completed, communication will not be started or resumed.

  By the way, in the communication system 1 of FIG. 3, if a problem occurs due to repeated insertion / removal of the USB cable 12, communication between the host device 2 and the device device 3 via the USB cannot be performed. In this case, the host device 2 temporarily stops the supply of the power supply 14 to the device device 3.

  At this time, as shown in (1) of FIG. 5, the voltage level of the power supply line 8 falls from a high level (High) (+5 V) to a low level (Low) (0 V).

  As the supply of the power supply 14 from the host apparatus 2 to the device apparatus 3 stops, as shown in (2) of FIG. 5, the voltage level of the power supply on the device side is also high (+ 5V). ) To low level (Low) (0V).

  As a result, pull-down is performed in which the plus-side data signal line 9 is connected to the ground GND via the plus-side pull-down resistor 17, and the host-side USB controller 5 of the host device 2 performs the pull-down as shown in FIG. The detected voltage level of the positive data signal line 9 is lowered from a high level (High) (+3 V) to a low level (Low) (0 V).

  In this way, the device device 3 is reset by lowering the voltage level of the plus-side data signal line 9 to a low level (Low) (0 V).

  By this reset, the host device 2 can recognize (simulate) that the device device 3 has been removed from the host device 2 (physically connected).

  Then, as shown in (1) of FIG. 5, when the host device 2 resumes the supply of the power supply 14 immediately after resetting, as shown in (3) of FIG. When the voltage level of 9 rises to a high level (High) (+3 V) again, it can be recognized that the device apparatus 3 is connected again.

  Thereby, the host apparatus 2 can perform the initialization process with respect to the device apparatus 3 again, and can restart communication.

JP-A-7-182070

  However, in the case where the device apparatus 3 is an apparatus having an internal power supply such as a mobile phone, the positive data signal line is always provided regardless of whether the power supply 14 is supplied from the host apparatus 2 to the device apparatus 3 or not. 9 may be pulled up.

  In such a case, as shown in (3) of FIG. 6, even if the supply of the power supply 14 from the host device 2 to the device device 3 is temporarily stopped, as shown in (1) of FIG. The voltage level of the plus-side data signal line 9 detected by the host device 2 (host-side USB controller 5) cannot be lowered to a low level (Low).

  As a result, the host device 2 cannot reset the device device 3 and cannot perform initialization processing on the device device 3.

  Although it is conceivable to modify the host driver of the host device 2 so that the device device 3 can be reset, the host driver is usually in a black box and cannot be repaired in many cases.

  Therefore, conventionally, there has been a problem that the initialization process cannot be performed on the device apparatus depending on the configuration of the device apparatus.

Therefore, the present invention has been made in view of such a problem, and the initialization process for the device device by the host device can be reliably performed. As a result, communication between the host device and the device device can be performed. It is an object of the present invention to provide a communication system that can be reliably started or restarted.

To achieve the above object, a communication system according to the present invention, a host device, a device unit having a power supply therein, a communication system connected via a bus, the device apparatus in the host device to but on the data signal line of the bus connected, in a state in which the device apparatus is connected via the bus to the host device, by lowering the voltage level of the data signal lines from a high level to a low level, Brighter set circuit by resetting for initialization is provided to the device apparatus, wherein the host device to supply power to the device units via a power supply line of the bus And a reset signal is supplied to the reset circuit in conjunction with stopping the supply of the power to the device device. And the reset circuit is configured to apply the reset to the device device when the reset signal is supplied, and the host device causes the device device to be turned on by the reset device. When the voltage level of the data signal line rises again to the high level by restarting the supply of power to the device device, the device device is reconnected to the host device. It is characterized in that it is configured to perform the initialization process on the device device in a false manner . According to such a configuration, the device device can be surely reset by lowering the voltage level of the data signal line to a low level. Further, the device apparatus can be reliably reset by lowering the voltage level of the data signal line to a low level in conjunction with the stop of the supply of power to the device apparatus.

Further, in the communication system according to the present invention, the reset circuit is switched from an off state to an on state when the reset signal is supplied, and the data signal line is connected to the ground in the on state, whereby the data A switching element for reducing the voltage level of the signal line to the low level is provided. And according to such a structure, it becomes possible to reset with respect to a device apparatus by the simple structure provided with the switching element.

Furthermore, the communication system according to the present invention is characterized in that the bus is a USB bus. According to such a configuration, the device device can be reliably reset by lowering the voltage level of the data signal line in the USB bus to a low level.

The communication system according to the present invention is characterized in that the host device is a hands-free vehicle-mounted device or a vehicle-mounted navigation device, and the device device is a mobile phone. According to such a configuration, the voltage level of the data signal line in the bus connecting the hands-free in-vehicle device or the in-vehicle navigation device and the mobile phone is lowered to a low level, thereby reliably resetting the mobile phone. Can be applied.

According to the communication system according to the present invention, the device device can be reliably reset by the reset circuit. As a result, the initialization process for the device device can be performed reliably. As a result, the host device and the device device Can be reliably started or restarted.

  Further, by forming such a reset circuit with a simple configuration including a switching element, it is possible to reduce the size and cost of the apparatus.

  Furthermore, the present invention is effectively applied to communication between a host device and a device device via USB and communication via a bus between a hands-free in-vehicle device or an in-vehicle navigation device and a mobile phone. be able to.

Hereinafter, an embodiment of a communication system according to the present invention will be described with reference to FIGS. 1 and 2.

  Note that portions having the same or similar basic configuration as those in the related art will be described using the same reference numerals.

  FIG. 1 shows a host device 19 that communicates with the above-described device device 3 (simply shown in FIG. 1) via USB.

  The host device 19 is provided with the host-side USB controller 5 as in the prior art.

  The host device 19 includes three USB buses 8, 9, and 10 including a power supply line 8, a positive data signal line 9, and a negative data signal line 10 as USB buses to which the device device 3 is connected. It is arranged so as to be connected to the side USB controller 5. The host device 19 (host-side USB controller 5) is connected to a ground line (not shown) as one of the USB buses.

  Further, a first positive pull-down resistor 20 having a predetermined resistance value (15 kΩ in FIG. 1) is connected between the positive data signal line 9 and the ground GND.

  Further, a first negative pull-down resistor 21 having the same resistance value as that of the first positive pull-down resistor 20 is connected between the negative data signal line 10 and the ground GND.

  A reset circuit 23 in the present embodiment is disposed on the plus side data signal line 9 and the minus side data signal line 10.

  As shown in FIG. 1, the reset circuit 23 has a plus side switching element 24 as a switching element corresponding to the plus side data signal line 9, and the plus side switching element 24 is formed by an npn transistor. Has been.

  Between the collector terminal C of the plus side switching element 24 and the plus side data signal line 9, a second plus side pull down resistor 26 having a lower resistance value (100Ω in FIG. 1) than the first plus side pull down resistor 20. Is connected.

  The emitter terminal E of the positive side switching element 24 is connected to the ground GND.

  A host processor 28 is connected to the base terminal B of the plus side switching element 24 via a reset signal line 27. The host processor 28 is connected to the host-side USB controller 5.

  When the host processor 28 starts or resumes communication between the host apparatus 2 and the device apparatus 3, the host processor 28 is connected to the host apparatus 19 via the USB buses 8, 9, and 10. A reset signal is supplied to the plus side switching element 24 via a reset signal line 27.

  The reset signal may be supplied in conjunction with stopping the supply of the power supply 14 to the device device 3 (see FIG. 2).

  The positive side switching element 24 is switched from an off state to an on state when a reset signal is supplied from the host processor 28.

  In the ON state, the plus side switching element 24 connects (pulls down) the plus side data signal line 9 to the ground GND via the second plus side pull down resistor 26.

  Thereby, the voltage level of the plus-side data signal line 9 detected by the host-side USB controller 5 of the host device 19 can be forcibly lowered from a high level to a low level, and the device device 3 is reset. Can be done.

  Further, as shown in FIG. 1, the reset circuit 23 has a minus side switching element 25 as a switching element corresponding to the minus side data signal line 10, and the minus side switching element 25 is a plus side switching element. Similarly to 24, it is formed of an npn type transistor.

  Between the collector terminal C of the minus side switching element 25 and the minus side data signal line 10, there is a second minus side pull down resistor 30 having the same resistance value (100Ω in FIG. 1) as the second plus side pull down resistor 26. It is connected.

  The emitter terminal E of the negative side switching element 25 is connected to the ground GND.

  A host processor 28 is connected to the base terminal B of the negative side switching element 25 via a reset signal line 27. The host processor 28 supplies a reset signal to the minus side switching element 25 through the reset signal line 27 as in the case of the plus side switching element 24.

  The minus side switching element 25 is switched from an off state to an on state when a reset signal is supplied from the host processor 28. In the on state, the minus side data signal line 10 is connected to the ground GND via the second minus side pull-down resistor 30. Is connected (pull-down).

  Thereby, the voltage level of the minus side data signal line 10 detected by the host side USB controller 5 of the host device 19 can be forcibly lowered from a high level to a low level, and the device device 3 can be reset. It is like that.

  Next, the operation of this embodiment will be described.

  Here, in the initial state, the host device 19 supplies the power supply 14 to the device device 3 via the power supply line 8 under the control of the host-side USB controller 5, as shown in FIG. It is assumed that the voltage level of the power supply line 8 detected by the host-side USB controller 5 of the host device 19 is at a high level (High).

  Further, (2) in FIG. 2 shows the voltage level of the reset signal line 27 detected by the host processor 28 of the host device 19, and this voltage level is “High” from the host processor 28. This indicates that the reset signal is supplied to the plus side switching element 24, while the voltage level of “Low” indicates that the reset signal is not supplied. As shown in (2) of FIG. 2, in the initial state, the reset signal is not supplied to the plus side switching element 24, and the plus side switching element 24 is in the off state.

  Further, as shown in (3) of FIG. 2, in the initial state, the voltage level of the plus side data signal line 9 recognized by the host device 19 is at a high level (High) by pull-up, and the plus side data It is assumed that communication for transmitting data from the host device 19 to the device device 3 is performed via the signal line 9.

  The host-side USB controller 5 temporarily stops the supply of the power supply 14 to the device device 3 after communication cannot be performed for some reason from the initial state.

  At this time, as shown in FIG. 2 (1), the voltage level of the power supply line 8 falls from a high level (High) to a low level (Low).

  At this time, as shown in (2) of FIG. 2, the host processor 28 sends a reset signal (“High” in (2) of FIG. 2) to the plus side switching element 24 of the reset circuit 23 via the reset signal line 27. Voltage level signal).

  As a result, the plus-side switching element 24 is switched from the off state to the on state, and the pull-down in which the plus-side data signal line 9 is connected to the ground GND through the second plus-side pull-down resistor 26 is performed.

  As a result, even if the device apparatus 3 has an internal power supply and the positive data signal line 9 is always pulled up, as shown in FIG. The voltage state of the plus-side data signal line 9 detected by the host-side USB controller 5 can be forcibly lowered from a high level (High) to a low level (Low) to reliably reset the device device 3. it can.

  By this reset, the host device 19 can recognize (simulate) that the device device 3 has been removed from the host device 19.

  Then, as shown in (1) of FIG. 2, when the host device 19 resumes supplying the power supply 14 to the device device 3 immediately after the reset, the host device 19 performs another pull-up as shown in (3) of FIG. When the voltage level of the plus side data signal line 9 rises again to a high level (High), it can be recognized that the device apparatus 3 is connected again.

  Thereby, the host apparatus 19 can perform the initialization process with respect to the device apparatus 3 again, and can restart communication.

  As described above, according to the present embodiment, the device circuit 3 can be reliably reset by the reset circuit 23. As a result, the initialization process for the device apparatus 3 can be performed reliably. Communication between the host apparatus 19 and the device apparatus 3 via the USB can be reliably started or restarted.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed.

  For example, the host device 19 may be a hands-free vehicle-mounted device or a vehicle-mounted navigation device, and the device device 3 may be a mobile phone.

  Further, the plus side switching element 24 and the minus side switching element 25 may be formed by transistors other than npn transistors.

  Furthermore, the supply of the reset signal to the plus side switching element 24 and the minus side switching element 25 is performed when the supply of the power supply 14 to the device device 3 as described above is stopped (in other words, when the communication is resumed). Not limited to this, it may be performed at any time when the device apparatus 3 is reset (for example, when communication is started).

  Furthermore, as a bus, a bus other than USB may be used as long as the present invention can be effectively applied.

Shown to circuit diagram of an embodiment of a communication system according to the present invention The time chart which shows the effect | action of a reset circuit in embodiment of the communication system which concerns on this invention The figure which shows the communication system provided with the circuit structure of USB conventionally employ | adopted Time chart showing the operation of the communication system of FIG. Time chart showing ideal reset operation of communication system of FIG. Time chart showing conventional problems

Explanation of symbols

3 Device Device 9 Positive Data Signal Line 10 Negative Data Signal Line 19 Host Device 23 Reset Circuit 24 Positive Switching Element 25 Negative Switching Element

Claims (4)

A communication system in which a host device and a device device having an internal power supply are connected via a bus,
On the data signal line of the bus that the device apparatus in the host device is connected, in a state in which the device apparatus is connected via the bus to the host device, the voltage level of the data signal lines from a high level by lowering the low level, lapis lazuli set circuit by resetting for initialization is provided to the device units,
The host device is configured to supply power to the device device via a power supply line of the bus, and in conjunction with stopping the supply of power to the device device. Formed to supply a reset signal to the reset circuit,
The reset circuit is configured to apply the reset to the device device by being supplied with the reset signal,
The host device assumes that the device device has been removed from the host device by the reset, and then restarts the supply of power to the device device, whereby the voltage level of the data signal line is again increased to the high level. The device device is configured to perform the initialization process on the device device by assuming that the device device is reconnected to the host device.
A communication system characterized by the above . The reset circuit is switched from an off state to an on state when the reset signal is supplied, and the voltage level of the data signal line is set to the low level by connecting the data signal line to the ground in the on state. The communication system according to claim 1, further comprising a switching element to be lowered. The bus is a communication system according to claim 1 or claim 2, characterized in that there is a USB bus. The communication system according to any one of claims 1 to 3 , wherein the host device is a hands-free in-vehicle device or an in-vehicle navigation device, and the device device is a mobile phone. .

Images