WO1998029944A1

WO1998029944A1 - Interface

Info

Publication number: WO1998029944A1
Application number: PCT/GB1997/002231
Authority: WO
Inventors: Michael Dacey
Original assignee: A-Level Software Limited
Priority date: 1997-01-02
Filing date: 1997-08-19
Publication date: 1998-07-09
Also published as: GB9700014D0; AU4022497A

Abstract

Method and apparatus for converting a signal from an infra red remote controller to an asynchronous signal which can be applied to a computer and stored in the memory of the computer for subsequent retransmissions by the computer or to allow control of the computer using the remote control handset by assigning functions to the stored codes. The method comprises the steps of demodulating the pulse coded infra red signals, generating a start bit and a stop bit and combining these to give the asynchronous signal.

Description

INTERFACE

Background to the invention

Many home appliances, especially televisions and video recorders, may be controlled by an infra red remote control signal from a remote control handset. In this way, the appliance may be controlled simply and at a large distance from the appliance.

Typically on pressing a button on the remote control handset, widely spaced bursts of infra red light are transmitted by the handset. These bursts are repeated whilst the button remains depressed. Each burst contains a pulse code which is dependent upon the key depressed. The pulse code is modulated on a high frequency carrier, typically of between 30kHz and 40kHz in frequency. The pulse code is decoded by the appliance to be controlled.

A problem with conventional remote control systems is that each remote control handset is dedicated for use with a particular appliance, and therefore it is necessary to have a separate handset for each appliance to be controlled. In recent years, manufacturers have increased the number of pulse codes stored by the remote control handsets for their appliances so that a single handset can control associated appliances, for example so that a single remote control handset can control both a television and video recorder. By pre-storing sufficient codes, a remote control handset can even control other manufacturer's appliances. This requires that the remote control is manufactured knowing a large number of pulse codes for different appliances, many of which will never be used.

Prior Art

Recently a 'teachable' remote control handset has become available. This includes an infra red receiver which receives an infra red signal transmitted from the dedicated handset of an appliance, a memory which is able to store a signal corresponding to the received signal, and an infra red transmitter which is able to reproduce the infra red pulse code from the stored information. Such devices are expensive, and require teaching from an existing, dedicated, remote control handset. Such devices have no means of displaying accurately the function associated with a particular button.

Summary of the present invention

According to a first aspect of the present invention, an interface comprises: an infra red receiver for receiving and demodulating an infra red signal from an infra red remote controller; a start bit generator; a stop bit generator; and, a means for combining the demodulated infra red signal, the start bit and the stop bit to generate an asynchronous bit pattern representative of the infra red signal .

With the interface according to the present invention, infra red signals from a remote control handset in the form of pulse codes transmitted in a series of spaced apart bursts of pulses can be converted into asynchronous data with a start bit and a stop bit which can be input to the serial port of a computer. This allows the remote control handset to be used to control the computer in addition to controlling the appliance for which it is intended. This gives many potential applications as discussed in detail later.

It is preferred that the start and the stop bit generator is a decimal or decade counter. In this case, a clock signal can be applied to the decimal counter which will generate a start bit and a stop bit separated by eight bits in which data is included. The clock signal is preferably about equal to or an integral multiple of the frequency of the high frequency carrier of the remote control signal. The asynchronous bit pattern is advantageously applied to the serial input port of a personal computer, and is stored in the memory of the personal computer. By storing the data in a computer, the data can later be accessed, thereby making possible the applications referred to below. The baud rate of the serial port of the computer is advantageously equal to the frequency of the clock signal.

Where the data is stored in a computer, a function is preferably associated with each of the codes which are stored. In this way, by retransmitting the infra red signal to the computer, the computer can execute the function associated with the code. For example, where the computer is used as part of a presentation, a speaker can associate each of the stored codes with a function such as to start a video player, start playing a compact disc, or display an image on the computer screen, and these functions can be executed remotely by the speaker.

Where the signal is applied to a computer, an infra red light source is preferably connected to the serial port of the computer. In this way, the asynchronous data stored by the computer can be output to the infra red light source to transmit infra red signals to control the appliance to which that code applies. This allows the computer to control the appliance rather than the appliance being controllable only by a dedicated remote control handset. For example, it would be possible to store all the codes associated with functions of a television remote control in the computer, and then transmit an infra red code from the computer to control the television. It is preferred that the infra red light source is an infra red light emitting diode, and in any case it is preferred that the output of the computer is applied to an amplifier which drives the light source to give an intense infra red signal.

The output of a particular code may be in response to a direct input to the computer, for example through a keyboard or by using a mouse both by controlling the position of the pointer and by the mouse buttons. In this case, it is beneficial for the computer to display icons or other images which correspond to the functions of the codes stored by the computer so that a user can select the required function easily. This is advantageous over conventional hand held remote control units in which the only indication of the function which a particular button will effect is a small, preprinted symbol on the handset. Alternatively, the output of a particular code may be in response to an input external to the computer, for example by a signal received by the computer through a modem. This allows a user to access his computer through a telephone line, and cause the computer to transmit an infra red signal to control other appliances in his home.

In any case, the output of an infra red signal from the computer to control an appliance may be timed, so that a user may preprogram his computer to control an appliance at a set future time.

According to a second aspect of the present invention, a method of converting an infra red signal to an asynchronous bit pattern for applying to a computer comprises the steps of: demodulating the infra red remote control signal; generating a start bit; generating a stop bit; and, combining the start bit and the stop bit with the demodulated infra red signal.

Brief description of the drawings

An example of the present invention will be described in accordance with the accompanying drawings, in which : Figure 1 shows a diagram of typical infra red remote control signals used for remote control of an appliance;

Figure 2 shows a block diagram of a first example of an interface circuit according to the present invention; Figure 3 shows a diagram of the signals of the interface circuit of Figure 2; Figure 4 shows a circuit diagram of a specific implementation of the interface circuit of Figure 2 ;

Figure 5 shows a block diagram of a second example of an interface according to the present invention; Figure 6 shows a circuit diagram of a specific implementation of the interface circuit of Figure 5; and,

Figure 7 shows a side view of an interface.

Detailed description of examples of the present invention Figure 1 shows a typical waveform of an infra red remote control signal. As shown in Figure la, the signal comprises a series of bursts of pulses, each burst being around 10ms in duration, and being separated by about 100ms. Within each 10ms burst, there is a series of coded pulses, the series of pulses depending upon the button depressed on the remote control handset . This is shown in Figure lb. Each pulse is itself a series of on/off pulses, typically having a frequency of between 30 and 40kHz, with a 50% duty cycle, as shown in Figure lc . The serial port of a personal computer is typically an asynchronous port so that there is no need for a common timer between the input device and the computer. However, this requires the input data to include at least a start bit, followed by the data and finally a stop bit. With the typical infra red remote control transmissions described above with respect to Figure 1, there are no start and stop bits. Therefore the signals cannot be input directly into the serial port of a computer.

The interface of the present invention demodulates infra red signals from an infra red remote control handset, and imposes start and stop bits to this data so that the data can be input through a serial port of a computer where the data can be stored in memory for subsequent use.

Two examples of an interface according to the present invention will be described. A first example, shown in block form in Figure 2, and as a detailed circuit diagram giving a concrete embodiment of a circuit in Figure 4, is designed for use with a clock frequency of 74kHz, about twice the frequency of a typical infra red carrier. The circuit shown in Figure 4 is primarily designed for input of the data to a Macintosh computer. A second example is shown in block form in Figure 5 and as a complete circuit diagram in Figure 6. This circuit includes an internal 38.4kHz clock which matches a possible baud rate of an RS232 serial port of most personal computers, and is therefore suited to use with such computers. This frequency is also equal to or an acceptable compromise to the high frequency carrier of most conventional infra red remote control signals.

The interface shown in Figure 2 includes an infra red receiver and demodulator (IC1) . On receipt of pulse coded infra red radiation from an infra red remote control handset, this receiver and demodulator outputs a signal corresponding to the high and low levels of infra red radiation received. In general, the demodulator output is normally high, and goes low when a pulse is received, and therefore the output is applied to an inverter (INI) to give a signal corresponding to the light signal received. A typical output signal of the inverter is shown in Figure 3d.

The interface includes a standard clock pulse generator (IC2), for example a 555 timer. This generates a clock pulse at a frequency of about 74kHz, approximately twice the frequency of the high frequency carrier used for conventional infra red remote control signals. The serial port of the computer is set at the same rate. To convert the data into asynchronous data with a start bit, a stop bit and eight data bits, the clock pulses are applied to a decade counter (IC3) . This counter has ten outputs, Y0-Y9. When the first clock pulse is input to the counter, the first output, Y0 , is switched high, and the remaining outputs Y1-Y9 stay low. On input of a subsequent clock pulse, Y0 switches low, and the next output, Yl, is switched high, with the other outputs remaining low. This is continued until all ten outputs have been switched high, and then the process is repeated. In this way, the output YO constitutes the required start bit of the final signal. The output Y9 is input to an inverter (IN2) , for example to both inputs of a NAND gate, to give the stop bit signal as shown in Figure 3c.

The inverted output of the demodulator is ORed with the start signal from output YO by applying the signals to an OR gate (0R1) . The resulting signal, as shown in Figure 3e, is input to a NAND gate (NAND1) together with the stop signal from the inverter (IN2) connected to Y9. This signal, and the inverse of this signal, are then input to the serial port of the computer.

The particular circuit shown in Figure 4 is designed for use with a Macintosh computer. The operating system for the Macintosh computer includes a serial driver which supports external clocking which ensures that the serial port of the computer operates at a rate exactly equal to the rate of the clock pulse generator of the device connected to the port. Therefore, the output of the clock generator (IC2) is applied directly to the input handshake pin (CTS) of the serial port. Where the interface is used for input to a serial port of a computer where this feature is not available, the clock pulse generator of the device is controlled to produce a clock pulse at the baud rate of the serial port of the computer.

The serial port of the Macintosh is an RS422 port. In this case, the DTR line is either at a high voltage of about +3v when the port is open, or at a low voltage of about -3v when the port is closed. When the port is open, the +3v from the DTR line is supplied to the positive rail of the circuit via a diode (Dl) . IC6 operates as a voltage doubler, and maintains the negative rail of the device at about -3v. The output signal from the interface unit is applied to the negative data receive of the serial port, and the inverted output signal is applied to the positive data receive of the serial port. In this way, there is always a 6v difference between the positive and negative data receive pins of the serial port, with the polarity of this voltage difference indicating a mark or space. The asynchronous data input to the serial port of the computer can be stored in memory, and used as required.

The positive and negative transmit data pins of the serial port are connected to an infra red light emitting diode (LED3) , either directly or through an amplifier (not shown) . The asynchronous data stored in the computer can be output to the light emitting diode (LED3) for transmission to the appliance to be controlled.

As the infra red signal for controlling an appliance must be modulated, it is necessary to modulate the output from the light emitting diode. This is achieved by zeroing alternate bits stored in the computer memory. As the serial port of the computer and the clock generator of the interface run at approximately twice the frequency of the high frequency carrier, this zeroing of bits will cause modulation of the lights to replicate the original control signal. By zeroing alternate bits, the modulation is generated by software rather than by hardware . The modulated output signal is shown in Figure 3g.

The alternative circuit, especially suited for conventional personal computers with an RS232 serial port is shown in Figures 5 and 6.

The interface includes a clock generator Ul which includes a 14-stage ripple carry binary counter, the sixth stage of which is combined with a 2.4576MHz crystal to generate clock pulses with a frequency of 38.4kHz. This frequency is equal to, or is a satisfactory compromise to, the typical high frequency carrier on which conventional infra red control signals are modulated. These clock pulses are applied to a decimal counter U4 corresponding to that of the first example to produce a start and a stop bit separated by eight spaces for the data. The start and stop bits are combined with the demodulated infra red control signals applied to the infra red detector and demodulator via two NOR gates, and the resulting signal is inverted and applied to a standard RS232 transmitter/receiver U2 which converts the TTL level signals into the required RS232 line levels. The signal is then applied to the RS232 port of a computer, where the codes are stored in memory as described above.

To transmit the signals, the codes are sent through the RS232 port of the computer and the RS232 transmitter/receiver U2 after which they are combined with the clock pulse from the clock pulse generator Ul via a NAND gate to give the required modulated signals which drive the infra red transmitter to transmit the infra red remote control signals. To achieve the required modulation of the output infra red light, the serial driver is used to Set Break and Clear Break. When a break is set, output from the transmitter in inhibited, and when the break is cleared, transmission is enabled. By setting and clearing breaks at the correct time intervals, the output will be modulated. It is possible that the modulation may be achieved by hardware provided in the interface circuitry.

The circuit shown in Figure 6 also includes a power supply. This is activated through the DTR line of the RS232 port when the port is activated, and provides a 5v supply to the interface circuitry. By activation of the power supply via the DTR line, battery power can be conserved when the serial port is not activated.

As shown in Figure 7, with either example according to the present invention, the infra red transmitter is provided on a flexible arm. This allows the interface to be provided near the computer with the infra red receiver pointing in one direction for receiving signals from the infra red remote controller handset, whilst the infra red transmitter is directed towards the device to be controlled. It is possible to provide the infra red receiver on a flexible arm, either instead of providing the transmitter on a flexible arm or in addition to providing the infra red receiver on such an arm, and still allow the interface to receive from and transmit to devices at different relative locations to each other. The interface according to the present invention has a large number of possible applications. One application is for a user to teach the computer the infra red signals from an existing dedicated remote control handset for the control of existing appliances, and for the computer to then be able to control the appliances. In this case, the user would point their existing dedicated remote control handset to the infra red receiver of the interface, so the interface receives the infra red signals transmitted from the handset, stores these in memory, and is able to reproduce the signals using its infra red transmitter. By storing the codes in a personal computer, rather than in a remote control handset, there is a large capacity for storing the codes of a large number of remote control handsets, and icons which represent closely the functions available can be displayed. This makes selection of the required function much easier than on a hand held remote control with which the functions performed by any particular button can only be displayed as a small preprinted symbol, for example a number. Further, re- transmission of a required code can be initiated easily using a mouse or other simple input device which is pointed to the appropriate icon. The computer can also allow a sequence of codes to be recorded, and repeatedly transmitted, and may allow one or more codes to be transmitted at a predetermined time. For example, if the system is able to remotely control the drawing of curtains, or operation of lighting or central heating, the computer can be programmed to automatically activate these devices at a required time, for example to give the appearance that premises are inhabited to deter burglars, or to heat the premises and turn on the lights for when the occupant comes home. By linking the computer to a modem, codes can be transmitted to control appliances from outside the premises, or, where the computer has a voice recognition system, allow applicances to be controlledin response to verbal instructions from a user. In addition, a conventional remote control handset for an existing appliance can be used to control the computer or peripherals of the computer. In this case, the remote control handset is aimed at the infra red receiver of the device according to the present invention, and the buttons on the handset are pressed so that the infra red pulse codes are sent to the computer and stored by the computer. In the memory of the computer, each of the codes is associated with a particular function, so that when the computer receives the code again, the appropriate function is executed. Functions which can be executed include control of a CD player which is playing audio or video signals through the computer, as well as conventional programs which can be executed on the computer, for example graphic displays. This method of control of the computer is often more simple than input of commands using a keyboard or mouse, and allows the user to be remote from the computer when the commands are instructed. This is particularly advantageous where the computer is used as part of a presentation package where the speaker is able to be remote from the computer, yet can control the computer easily when required. The remote control codes may be associated with control of a pointer on the computer screen, allowing remote control to replicate the normal control using a mouse. Another example of the use of remote control of the computer is for an Internet Web Browser, which allows the user to browse through the Worldwide Web from the comfort of his arm chair rather than from at his computer keyboard.

When the computer is used to access the Internet, the programs can be down loaded to the computer and executed by the use of Java (Trade Mark) . This is a platform independent programming language supported by most operating systems. When a web page is downloaded, a Java program (or "applet") can be downloaded simultaneously and executed by the computer.

When used in conjunction with the interface according to the present invention, identifiers may be included in a web page to cause transmission of infra red signals to control appliances. In this case, the user must associate the stored code with the appropriate identifier.

Claims

1. An interface comprising: an infra red receiver for receiving and demodulating an infra red signal from an infra red remote controller; a start bit generator; a stop bit generator; and, a means for combining the demodulated infra red signal, the start bit and the stop bit to generate an asynchronous bit pattern representative of the infra red signal.

2. An interface according to claim 1, in which the start and the stop bit generator is a decimal or decade counter.

3. An interface according to claim 1 or 2 , in which the clock signal is equal to or an integral multiple of the high frequency carrier of the remote control signal.

4. A system including the interface of any one of the preceding claims, in which the asynchronous bit pattern is applied to the serial input port of a personal computer, and is stored in the memory of the personal computer.

5. A system according to claim 4, in which a function is associated with each of the codes stored in the memory of the computer, and in which the computer executes the function associated with a code transmitted subsequently.

6. A system according to claim 4 or 5 , in which an infra red light source is connected to the serial port of the computer, and in which the asynchronous data stored in the memory is output to the infra red light source to transmit infra red signals to control the appliance to which that code applies.

7. A system according to claim 6, in which the infra red light source is an infra red light emitting diode.

8. A method of converting an infra red signal to an asynchronous bit pattern for applying to a computer comprising the steps of: demodulating the infra red remote control signal; generating a start bit; generating a stop bit; and, combining the start bit and the stop bit with the demodulated infra red signal .