CN1719486A - Circuits and Interfaces for Remote Controllers Equipped with Hold Buttons - Google Patents

Abstract

A remote control with a two-wire interface has control keys associated with resistors. The interface circuit of the controlled device converts the impedance value that can be measured between the terminals of the two-wire interface into commands. The holding switch is configured so that a direct current path is always present independent of the position of the holding switch. Design the interface circuit of the controlled device so that it can detect the operation of the control keys and can issue a message or indication even when the device is in low power or shutdown mode and the hold switch is activated. The user is thereby notified about the state of the hold key.

Description

Circuits and Interfaces for Remote Controllers Equipped with Hold Buttons

technical field

The present invention relates to remote controls for electronic devices, and more particularly to wired remote controls for use in portable devices.

Background technique

A remote control unit for a device such as a portable audio system is required to have several buttons, the pressing of any one of which can be detected by the device and used to control the operation of the system. For example, a remote control unit for an audio system can have buttons to increase and decrease volume, change pitch, balance left and right, and the like.

A known way for establishing communication between the remote control unit and the controlled device involves the use of a microcontroller and a common data bus, but would be complex and costly to implement.

Another known less expensive way would be to use a wired connection between the remote control unit and the device being controlled, wherein when a button in the remote control unit is pressed the impedance value between the control wires changes. The remote control unit in this case comprises a network of resistors connected to the control wires via a push button operated switch.

One known switched resistor circuit is the R-2R resistor ladder network. In this network, resistors of value R are connected in series with each other, and the last resistor is connected to one of the control lines of the remote control unit. One end of parallel resistors each having a value of 2R is connected to one end of each series resistor. Connect the other end of each shunt resistor to ground or supply voltage through a single pole double throw switch. The voltage on the output line varies in this circuit with the combination of switches activated by the buttons of the remote control unit. The downside of this circuit is that it requires the use of expensive double throw switches.

Another known resistor network is the so-called binary network, in which resistors are connected in parallel with each other across two control lines, each resistor being connected in series with a corresponding single pole single throw switch. As implied by the name of this network, the resistors have values in ratios of 1:2:4:8:16 and so on. For some applications, an advantage of this circuit is that it can detect any combination of simultaneous switch presses. However, the maximum number of switches that the circuit can unambiguously detect is limited by tolerances and variations in resistor values, voltage drift, electrical noise, and the like.

In some applications, such as the example given above, the user should not operate more than one switch at a time to control the main device. The device must likewise recognize multiple button presses simultaneously and ignore them. In this case it is not essential that the device be able to recognize which several buttons are pressed simultaneously. However, there is still a need to maximize the number of switches for a given resistor value tolerance and supply voltage drift.

All of the above remote controls can be equipped with a hold switch or key, which prevents unwanted operation of the device. Typically, a maintained switch is a series unipolar switch that interrupts one of the control lines when it is activated. If any of the control buttons is pressed while the hold button is activated, the impedance will remain infinitely high due to the interruption of the DC path. Unwanted operations are thus blocked.

However, the user may not remember that the hold key was activated, or activate the hold key unintentionally. Then, if the user wants to operate the device, the user may be misled into thinking that the device is not working properly or is malfunctioning.

In Fig. 1 a remote control according to the prior art is shown. During standard operation, hold switch 11 is closed. Disconnect control switches 2, 4, 7 and 9. Each of the control switches 2, 4, 7 and 9 is arranged in series with the control resistors 1, 3, 6 and 8, respectively. When the user operates one of the control switches 2 , 4 , 7 or 9 , there is a corresponding resistance value between terminals 12 and 13 . The relevant interface circuit of the controlled device detects and estimates the impedance value and executes the command corresponding to the corresponding impedance value. When the holding switch 11 is turned off, the direct current path is interrupted. If the user now operates any of the control switches 2, 4, 7 and 9, no DC current flows. The impedance value that can be measured between terminals 12 and 13 remains infinitely high, and it is impossible to detect that the control key has been actuated.

The remote control or the controlled device or both are often equipped with a display capable of displaying alphanumeric messages. In this case, while activating the hold key, it is desirable to notify the user that the hold key is activated when the control key is pressed.

However, portable electronic devices often require the lowest possible power consumption to maximize battery life. So, when the portable electronic device is turned off, the display is also turned off. When the device is switched off and the hold key is activated, the device can be powered on to issue a message on the display informing the user of the currently activated hold key.

Contents of the invention

Therefore, it is desirable to provide a remote control that allows changing operating conditions or power modes of connected electronic devices, especially from low power standby to higher operating levels, in order to inform the user about the current status of the hold keys. In the following, the term power mode is used to describe the "off" or "on" operating conditions. However, it is also conceivable that a device according to the invention proposes more than two power modes, for example an additional power mode, which only considers switching on the display for issuing messages. It is also desirable to provide a remote control interface for the remote control of the present invention. Ultimately, it is desirable to provide a method of operating a remote control interface of a device using the remote control and interface of the present invention.

This object is achieved by a remote control unit as set forth in claim 1 . The second object of the present invention is achieved by an interface circuit for a remote control as given in claim 5 . The third object of the present invention is achieved by a method for operating a device using a remote control as given in claim 9 . Further developments and alternative embodiments of the invention are shown in the corresponding dependent claims.

The remote controller of the present invention has a two-wire interface for communicating with the controlled device. The remote also displays one or more buttons or switches with corresponding associated resistors. When a button or switch is actuated, the value of the corresponding resistor can be measured at the two-wire interface, ie between two wires. The resistors can also work in combination with resistors built into the controlled device, forming a voltage divider. All these methods of determining the value of the corresponding resistance value should be included in the principles of the present invention. Different resistor values are unambiguously associated with different switches of the remote control, and thus with different functions of the controlled device. The hold buttons or switches are configured in the circuit in such a way that if any one of the control buttons is pressed or operated, a DC path always exists independently of the position of the hold switch. The remote controller of the present invention is characterized in that it is in a low power consumption state when the hold key is activated, when considering the convenience of user connection even in low power or off mode.

In a first embodiment, a series unipolar switch is used as the holding switch, which bypasses a holding resistor connected in parallel to the holding switch. When the hold key is activated, the switch is open. The impedance that can be measured if any of the control keys is pressed is increased by the series connection of the corresponding control resistor and hold resistor. By choosing the value of the hold resistor appropriately, an activated hold key can be unambiguously identified. Since there is a DC path when any control key is operated, the current can be used to change the power mode of the device from standby to a higher operating level, which allows, for example, a message to be displayed on a display. In case the device is already operating, it is not necessary to change the power mode.

In a second embodiment of the invention, the hold button is activated when the hold resistor is bypassed. Therefore, select the impedance value associated with the corresponding control button or key.

In a third embodiment of the invention, the hold key induces a current flow when the hold key is activated. For example, a hold button is a single pole hold switch that is connected in series with a hold resistor and between two wires of the remote control interface. Therefore, the current in hold mode and the hold resistor are chosen to be too small for changing power modes, ie starting the controlled device when the device is not operating. If any control key is operated during hold mode, the total impedance consists of the hold resistor connected in parallel with the resistor associated with the control key. The current generated by the parallel connection of the two resistors is high enough to change the power mode, ie to activate the connected device. In the power mode, which is equivalent to the operating mode, the connected device detects said impedance and compares it with all the values associated with the control keys. If no match is detected between the measured impedance value and the list of permissible impedance values, it is assumed that the hold key was actuated. So, post the message.

The impedance values of the control and hold resistors are chosen such that a hold resistor is always distinguished from any combination of control resistors. By using an appropriate impedance value, it does not matter whether the holding resistor is connected in series or in parallel to the control resistor.

The interface that detects the operation of the control key when the hold key is activated detects the current through the remote controller and sends a signal to the control circuit in the controlled device. When in a power mode equivalent to "off", the control circuit changes the power mode of the controlled device and issues a message informing the user about the current condition of the hold key. If the device has been operated, detection circuitry detects the impedance at the remote control interface and compares the detected impedance to stored impedances associated with control functions. If there is no match between the measured impedance and the stored impedance for the control function, it is assumed that the hold key is activated. Posts a message notifying the user about the current condition of the hold key.

A method for operating a device by a remote control having a hold switch which when activated prevents operation of the device, the method comprising the steps of interpreting a detected impedance into an operation to be performed by the device. The method also includes detecting a DC path between terminals of the remote control, changing the power mode of the device, and signaling when a fault occurs to interpret the measured impedance into an action to be performed.

Description of drawings

The present invention will now be further described by way of example with reference to the accompanying drawings, in which

Figure 1 shows a remote controller known in the prior art;

Fig. 2 shows the first embodiment of the remote controller of the present invention;

Fig. 3 shows the second embodiment of the remote controller of the present invention;

Figure 4 shows a third embodiment of the remote controller according to the present invention;

Figure 5 shows a fourth embodiment of a remote controller according to the invention; and

Fig. 6 shows a schematic diagram of the interface circuit of the remote controller according to the present invention.

Detailed ways

Reference has been made to FIG. 1 in the description of the prior art, so no detailed description will be given.

A first embodiment of the remote control of the present invention is shown in FIG. 2 . During normal operation, switch 11 is kept closed and resistor 14 is bypassed. Disconnect control switches 2, 4, 7 and 9. Each of the control switches 2, 4, 7 and 9 is arranged in series with the control resistors 1, 3, 6 and 8 respectively. When the user operates one of the control switches 2 , 4 , 7 and 9 , there is a corresponding impedance value between terminals 12 and 13 . The relevant interface circuit of the controlled device detects and estimates the impedance value and executes the command corresponding to the respective impedance value. The impedance value can be chosen so that the interface circuit can simultaneously detect the closure of multiple control switches. When the holding switch 11 is turned off, the holding resistor 14 is connected in series with the control resistors 1 , 3 , 6 and 8 . However, as long as none of the control switches 2, 4, 7 and 9 are closed, no direct current flows. If the user now operates any one of the control switches 2, 4, 7 and 9, then direct current flows. The impedance value that can be measured between terminals 12 and 13 corresponds to the impedance of the control resistor associated with the operating switch plus the impedance of the holding resistor. The direct current allows the device to detect that a control key has been operated while the hold switch is active. The interface circuit which detects and estimates the impedance present between the terminals 12 and 13 is now enabled to detect the inhibition or operation of any control switch and at the same time determine that the hold switch is operated. The control circuitry of the device controlled by the remote control can now issue a message or any other indication to the user that the hold switch is activated, disregarding the command associated with the control key. If the device is in a low power or standby mode prior to any control switch operation, a DC current through the control resistor and holding resistor can be used to start the device. Activation of the device may be accomplished by first activating only the control logic that controls the display or other means for notifying the user. It should be noted that throughout all the figures, the number of all resistors shown in the figures is not limited to four. Any other suitable number of resistors required to control the connected device is possible.

A second embodiment of the remote control of the present invention is shown in FIG. 3 . In this figure, each of a plurality of control resistors 1, 3 and 6 is connected in series with a control switch 2, 4 and 7 respectively. The arrangement of control resistors and control switches is coupled in parallel between two wires connected to terminals 12 and 13 . When any control switch is operating, the relative impedance between terminals 12 and 13 can be measured. The hold resistor 14 and the hold switch 11 are configured to be connected in series. The arrangement of hold resistors and hold switches is coupled in parallel to the control resistor and control switch. When the hold switch 11 is operated, the impedance of the hold resistor can be measured between the terminals 12 and 13 . The hold impedance does not correspond to any control resistor, so the hold impedance is not interpreted as a command for the device. If any control switch is operated, the control resistor associated with the respective switch is coupled in parallel. The impedance values of the control resistor and the holding resistor are chosen such that any parallel connection of the control resistor and the holding resistor is not interpreted as a command.

Figure 4 depicts a third embodiment of the remote control according to the invention. In this figure, control resistors 1, 3 and 6 are arranged in series connection. Control switches 2, 4 and 7 are coupled after each control resistor when viewed from terminal 12. Depending on the control switch operated, the impedance that can be measured between terminals 12 and 13 corresponds to the sum of the individual impedances arranged in the subsequently closed circuit. The hold resistor 14 and the hold switch 11 are configured to be connected in series and coupled across the last control switch 7 of the control switch line. The total impedance that can be measured across terminals 12 and 13 includes all control resistors 1 , 3 and 6 and holding resistor 14 when holding switch 11 is operated. Therefore, there is always a DC path between terminals 12 and 13 when the hold switch is operated. The interface circuit deciphering the impedance value which can be measured whenever any control switch is operated can now determine that the hold switch of the remote control has been operated. Any change in impedance between terminals 12 and 13 caused by operation of the control switch is detected. Control circuitry coupled to the interface can now abort the command associated with the measured impedance value and notify the user that the hold switch was operated. As in the previous example, informing the user of the status of the hold switch can be accomplished by displaying a message on a display or by issuing a visual or audible indication.

Another embodiment of the remote control of the present invention is shown in FIG. 5 . This circuit basically corresponds to the circuit shown in FIG. 4 . Control resistors 1 , 3 , 6 and 8 are coupled in series and control switches 2 , 4 , 7 and 9 are arranged after each control resistor when viewed from terminal 12 . The last control switch in the control switch line is connected to the last control resistor so that the impedance value measured when the last control switch 9 operates is equal to the sum of the impedance values of all control resistors. As explained in FIG. 4 , operating the control switch produces a value, measurable between terminals 12 and 13 , associated with the control resistor. During normal operation, the holding switch 11 is closed, bypassing the holding resistor 14 . If the hold switch 11 is opened, the hold resistor 14 is coupled in series with the control resistor. Therefore, the total impedance measurable between terminals 12 and 13 when the control switch is operating increases by the value of the holding resistor. The control logic for measuring the impedance between terminals 12 and 13 is able to detect the presence of impedance between the terminals and interpret this impedance as a command to the controlled device. The impedance values of the control resistor and the holding resistor are chosen such that a series connection of the holding resistor and either control resistor will result in a determination that the holding switch is operated. Accordingly, the control circuit will issue an indication to the user that the hold switch has been operated and discard commands that would otherwise be interpreted.

Fig. 6 shows an exemplary interface circuit according to the present invention. The interface circuit shown in the figure is suitable for the remote controller in Figure 4. Connect terminal 12 of the remote control of Figure 4 to terminal RKEY. The terminal 13 of the remote controller of FIG. 4 is grounded and is not shown in the figure. It is assumed that the maintained switch is operated and that the maintained switch 14 can be measured between terminal RKEY and ground. The impedance is chosen so that the impedance to ground present by closing the hold switch and the hold resistor is insufficient to bring transistor Q701 into a conductive state. If either control switch is operated, the associated control resistor and holding resistor are coupled in parallel. The total impedance is lower than that of a single hold resistor. The impedance value is now low enough to bring transistor Q701 into conduction. However, this switches transistor Q700 into a conductive state. Transistor Q700 issues signal EN which can be used to enable the power supply. Once the power supply is activated, there are voltages VG and DDVCC. Transistor Q703 is now on. The impedance of transistor Q703 is small compared to the impedance of the control resistor and the hold resistor. The impedance value, which can be measured between terminals 12 and 13 of the remote control via an input to the interface circuit RKEY, can now be measured at the terminal REMOCON of the interface circuit essentially unchanged. Thus, the interface circuit of the present invention allows the power supply of the device to be activated even when the key is operated and the device is in standby mode in off mode.

Claims (12)

1. A remote control unit having two wires with corresponding terminals (12, 13) and one or more control resistors (1, 3, 6, 8) connected to Corresponding control switches (2, 4, 7, 9) are associated between the wires, where the impedance between the two terminals (12, 13) of the remote control unit is converted into corresponding functions or commands of the connected device, where the control switches Operation of (2, 4, 7, 9) affects the presence of a corresponding impedance between terminals (12, 13), and wherein said remote control unit also has a hold switch (11) for inhibiting operation of the device, characterized in that : When a control switch (2, 4, 7, 9) associated with a control resistor (1, 3, 6, 8) is activated, a DC path exists independently of the position of the hold switch (11). 2. Remote control unit according to claim 1, characterized in that a holding resistor (14) is associated with the holding switch (11). 3. Remote control unit according to claim 2, characterized in that the holding resistor (14) associated with the holding switch (11) is bypassed at one position of the holding switch (11). 4. Remote control unit according to claim 3, characterized in that there is no direct current path when the control switches (2, 4, 7, 9) are not operated. 5. Interface circuit for a remote control unit according to any one of the preceding claims, wherein said interface circuit comprises means for estimating the impedance present between two input terminals, characterized in that there is provided for A component that detects a DC path established between two input terminals. 6. An interface circuit according to claim 5, characterized in that said circuit further comprises means for causing a connected device to send a message regarding the hold switch position. 7. Interface circuit according to claim 6, characterized in that said means for causing a connected device to send a message comprises means for activating a power supply. 8. A portable device comprising an interface according to any one of the preceding claims 5 to 7. 9. A method of operating a device using a remote control, wherein said remote control is connected to a controlled device via a two-terminal connection, wherein the device has at least a first and a second power mode, the method comprising the steps of: During the second power mode, the impedance between the two terminals (12, 13) is measured, wherein the impedance depends on the operated control switch (2, 4, 7, 9); interpreting the measured impedance into an operation to be performed by the device; Wherein the remote controller has a hold switch (11) for inhibiting the operation of the device, the method also includes the following steps: during said first power mode, detecting a direct current path between two terminals (12, 13); activating the device to enter the second power mode; A signal is emitted upon interpreting the measured impedance as a failure of an operation to be performed by the device. 10. The method of claim 9, wherein the first power mode is a standby or shutdown mode and the second power mode is an operational mode. 11. The method of claim 9, wherein the signal is a visual or audible distinguishable signal. 12. The method of claim 9, wherein the visually distinguishable signal is a text message displayed on a display.

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