WO1999031867A1

WO1999031867A1 - Method and apparatus for providing a power adjustable infrared signal

Info

Publication number: WO1999031867A1
Application number: PCT/US1998/023783
Authority: WO
Inventors: Cris Steven Estanislao; William J. Macko; John B. Van Zile
Original assignee: Motorola Inc.
Priority date: 1997-12-18
Filing date: 1998-11-09
Publication date: 1999-06-24

Abstract

An electronic device which can determine if the electronic device is in close physical proximity to an external device (604) and in which the electronic device can communicate with using the electronic device's infrared transmitter; and reducing the power level (606) of the electronic device's infrared transmitter automatically, if it is determined that the electronic device is in close physical proximity to the external device (608).

Description

METHOD AND APPARATUS FOR PROVIDING A POWER ADJUSTABLE INFRARED SIGNAL

Field of the Invention This invention relates in general to electronic devices, and more specifically to a method and apparatus for providing an adjustable infrared signal.

Background of the Invention There are many electronic devices which use built-in infrared (IR) circuitry in order to allow the electronic devices to communicate with other remote devices. For example, some calculators have built-in infrared circuits which allow them to communicate with remote printers. Infrared links are cost effective solutions and are especially suited for portable electronic devices given that they are fairly simply to implement, do not take up much room on the electronic device's main printed circuit board (PCB) and are fairly inexpensive to design-in.

Infrared communication links however present several drawbacks over other types of communication links, such as RS-232 serial links, etc. One drawback to IR communications is that if the two devices which are communicating with each other are placed in very close physical proximity to each other, IR distortion may affect the communications if the IR transmitter(s) are operating at high IR power (intensity) levels. This problem typically comes about because the IR transceivers in the electronic devices may be set at a certain power level in order to guarantee IR communications at up to a certain distance (e.g., one meter) from the other device. In order to meet the distance specification, the IR transceivers are set with IR transmit power levels which will guarantee communications at the given distance (e.g., one meter, etc.), while still providing a high level of noise immunity in a typical use (e.g., office) environment. One standard setting body which sets such specifications for the industry is "The Infrared Data Association" (IrDA), which has been set up to establish standards for infrared communications. In order to be compliant with some of the IrDA standard(s), an IR transmitter must typically transmit at a high enough power level to guarantee communications at up to a certain distance (e.g., one meter) away from the remote device. Another problem typically encountered using IR communications is found when the IR transmitters (or transceivers) are designed into portable radio frequency (RF) communication devices such as two-way pagers, personal digital assistance (PDAs) having radio communications capabilities, etc. The problem in this environment is that the embedded IR circuitry can sometimes generate noise which affects the radio frequency transmissions of the device in question. This noise generation of the IR circuitry is sometimes worse at higher IR transmissions levels. A final problem typically found with the use of IR circuitry in portable electronic devices is that in situations were the IR transmissions are set at high power levels, the IR transceiver operation will increase the battery charge times for the portable electronic devices when the electronic device is being charged, if IR communications are taking place during the charging of the electronic device at such high power levels. A need thus exists for a method and apparatus which can provide a solution to the above mentioned problems.

Brief Description of the Drawings

FIG. 1 is a block diagram of an electronic device in accordance with the preferred embodiment of the present invention.

FIG. 2 shows a more detailed block diagram of the decoder /controller of FIG. 1 in accordance with the preferred embodiment of the invention.

FIG. 3 shows an electronic device in accordance with the preferred embodiment of the invention.

FIG. 4 shows a system in accordance with the invention which includes an electronic device and a remote device which can communicate with each other using IR communications.

FIG. 5 shows a schematic of the adaptive IR transceiver circuit in accordance with the invention.

FIG. 6 shows a flowchart highlighting the steps taken by the present invention in order to adaptively control the IR power level. Description of the Preferred Embodiment

Referring now to the drawings and in particular to FIG. 1, an electrical block diagram of an electronic device such as a selective call transceiver (e.g., a two-way pager, etc.) in accordance with the preferred embodiment of the present invention is shown. The selective call transceiver (communication device) 50 comprises an antenna 52 for intercepting transmitted radio frequency (R.F.) signals which are coupled to the input of a receiver section 54. The R.F. signals are preferably selective call (paging) message signals which provide a receiver address and an associated message, such as numeric or alphanumeric message. However, it will be appreciated that other well known paging signaling formats, such as tone only signaling or tone and voice signaling, would be suitable for use as well. The receiver 54 processes the R.F. signal and produces at the output a data stream representative of a demodulated address and message information. The demodulated address and message information are coupled into the input of a decoder/controller 56 which processes the information in a manner well known in the art. A power switch 70, coupled to the decoder/controller 56, is used to control the supply of power to the receiver 54, thereby providing a battery saving function as is well known in the art for use with selective call receivers. For purposes of this illustration, it will be assumed that the FLEX™ (FLEX a trademark of Motorola, Inc.) protocol for two-way paging which is well known in the art is used, although other signaling formats (e.g., POCSAG, etc.) could be utilized as well. When the address is received by the decoder/controller 56, the received address information is compared with one or more addresses stored in a code plug (or code memory) 64, and when a match is detected, the message is stored in memory. Optionally, an alert signal is generated to alert a user that a selective call message, or page, has been received. The alert signal is directed to an audible alerting device 58 for generating an audible alert or to a tactile alerting device 60 for generating a silent vibrating alert. Switches 62 allow the user of the selective call receiver to select between the audible alert 58 and the tactile alert 60 in a manner well known in the art.

The message information which is subsequently received is stored in memory (not shown) and can be accessed by the user for display using one or more of the switches 62 which provide such additional functions as reset, read, delete, etc. Specifically, by the use of appropriate functions provided by the switches 62, the stored message is recovered from memory and processed by the decoder/controller 56 for displaying by a display 68 which enables the user to view the message. A real time clock circuit 74 provides conventional timing features such as the information required to display time of day information on display 68. A paging transmitter 80 under the control of controller 56 transmits messages and user requests. A conventional antenna switch 82 selectively couples the transmitter 80 or receiver 54 to antenna 52.

A battery 86 provides power to the two-way pager 50. Preferably, battery 86 is a rechargeable battery variety such as those made using nickel-metal hydride cells, etc. Pager 50 also includes an internal infrared transceiver 84 for communicating with external devices. The internal infrared transceiver 84 will be discussed in more detail further below.

Although in the preferred embodiment an infrared transceiver 84 is used, it can be appreciated that if the pager 50 does not need to have bidirectional communication with the external devices, an infrared transmitter 84 could be utilized to transmit information out to an external device (e.g., a printer, etc.).

The controller /decoder 56 of FIG. 1 can be constructed utilizing a microcomputer as shown in FIG. 2, although other hardware arrangements as known in the art can also be used. FIG. 2 is an electrical block diagram of a microcomputer based decoder /controller suitable for use in the selective call receiver of FIG. 1. As shown, the microcomputer 56 can preferably comprise a MC68HC05 or MC68HC11 or other similar microcomputer manufactured by Motorola, Inc. which preferably includes an on-board display driver 114. The microcomputer 56 includes an oscillator 100 which generates the timing signals utilized in the operation of the microcomputer 56. A crystal, or crystal oscillator (not shown) is coupled to the inputs of the oscillator 100 to provide a reference signal for establishing the microcomputer timing. A timer /counter 102 couples to the oscillator 100 and provides programmable timing functions which are utilized in controlling the operation of the receiver. A RAM (random access memory) 104 is utilized to store variables derived during processing, as well as to provide storage of message information which are received during operation as a selective call receiver as previously discussed. A ROM (read only memory) 106 stores the subroutines which control the operation of the receiver as well as the routines required to perform the present invention. Although the RAM 104 and ROM 106 have been shown internal to the controller 56, these memory types can also include external memory devices coupled to the controller 56.

It will be appreciated that in many microcomputer implementations, the programmable-ROM (PROM) memory area can be provided by, or further include, an EEPROM (electrically erasable programmable read only memory). The oscillator 100, timer/counter 102, RAM 104, and ROM 106 couple through an address /data /control bus 108 to a central processing unit (CPU) 110 which performs the instructions and controls the operations of the microcomputer 56.

The demodulated data generated by the receiver is coupled into the microcomputer 56 through an input/output (I/O) port 112A. The demodulated data is processed by the CPU 110, and when the received address information is the same as the code-plug memory which couples into the microcomputer through an I/O port 112B, the message, if any, is received and stored in RAM 104. Recovery of the stored message, and selection of the predetermined destination address, is provided by the switches which are coupled to the I/O port 112A.

At the time a message is received, an alert signal can be generated which can be routed through the data bus 108 to an alert tone generator 116 that generates the alert signal which is coupled to the audible alert device 58 that was described above. Alternatively, when the vibrator alert is selected as described above, the microcomputer generates an alert enable signal which is coupled through data bus 108 to the I/O port 112B to enable generation of a vibratory, or silent alert.

The battery saver operation of pager 50 is controlled by the CPU 110 with battery saving signals which are directed over the data bus 108 to the I/O port 112A which couples to the power switch. Power is periodically supplied to the receiver to enable decoding of the received selective call receiver address signals and any message information which is directed to the receiver. Infrared communications to and from the infrared transceiver circuit 84 are coupled to the controller 56 via a universal asynchronous receiver transmitter (UART) 118. Information from the real-time clock 74 are also coupled to the controller via I/O port 112A. Information to be transmitted are acted upon by the CPU 110 and sent via bus 108 to I/O port 112B. Although not shown, a signal indicating that the pager 50 is docked in docking station 420 (see FIG. 4) is received via the I/O port 112B as well be discussed further below.

Referring now to FIG. 3, a top view of the two way pager 50 is shown. In the preferred embodiment the two way pager 50 comprises an electronic device such as a PAGEWRITER™ 2000 two-way pager, although the present invention can be used with any electronic device which requires or could use an IR circuit (e.g., a bi-directional transceiver or a unidirectional transmitter, etc.) as will be explained below. Operational control of the device is controlled by a keypad which includes a plurality of user controls which allows a user to move within different fields (user selectable) or button locations which are displayed on display 68. The general operation (except for the present invention) of a two way pager 50 is discussed in detail in the PAGEWRITER™ 2000 User' s manual which is hereby incorporated by reference. An IR port 302 found in the rear of pager 50 provides a port for IR transmissions to be sent and received by pager 50.

In FIG. 4, an IR system is shown which includes pager 50 and a docking/charging station 420. Docking station 420 includes a plurality of electrical contacts 410 (three are presented here) which mate with corresponding contacts 412 found on pager 50. These electrical contacts allow for the charging of the battery 86 found inside of pager 50 when the pager 50 is properly seated within the docking station 420. One of these contacts 412 is used by pager 50 to sense that it has been docked in the docking station 420 and that therefore pager 50 is in close physical proximity to the docking station 420. Several conventional design alternatives are available which allow a "docked" indication signal to be provided to pager 50 via the one input port 412. In a simple design, this indication signal can be produced by the docking station having a pull- down (or pull-up in an alternate design) resistor coupled to the corresponding contact port 410 which mates to the select one input port 412. In this example, when the pager 50 is properly seated within docking station 420 one of the pager controller's input ports via I/O port 112B is caused to go to a low voltage state (in the case one uses a pull-up resistor, the controller port would change state to a high voltage state) when the pager is docked. This signal indicates to controller 56 that the pager is in close physical proximity to the docking station 420 or other remote device. Other well known alternative designs could also be used to provide a signal to controller 56 that the pager 50 is docked. These alternative designs can include the use of switches (electrical or mechanical) which get activated and send a signal to the pager 50 when the pager 50 is docked, the use of pull-up or pull-down circuits which cause one of the ports in controller 56 to change voltage level state, etc. Another design for determining the docking of the pager 50 uses the fact that the charger /docking station 420 knows that pager 50 is docked by sensing a thermistor located within the pager's battery 86 when the pager is properly docked. The thermistor is sensed using one of the electrical contacts 410 which mates to a corresponding contact 412 located on the pager 50. This contact also known as the "sense line" detects the presence of the thermistor and causes the charger to commence charging the pager's batter 86 and causes a battery charging LED found on the docking station 420 to be lit. The pager's controller 56 via one of its input ports can also sense that the pager 50 has been docked to the docking station 420 by monitoring that particular port 412.

A battery cavity 414 which includes a set of electrical contacts 408 allows for the charging of a second (replacement) battery (not shown) while the two-way pager 50 is removed from the docking/charging station 420. The docking station 420 further includes a connector which accepts a power cord 406 which provides power to the docking station 420. The power cord is attached to a conventional block transformer which gets connected to an AC outlet. A communications cable 404 couples to the docking station via a RS232 connector found in the rear of the docking station 420. The communications cable 404 is connected at the other end to a personal computer (PC) so that information (e.g., personal phone book information, data, etc. ) can be shared and downloaded between the PC and pager 50 while the pager is docked. Communications between pager 50 and docking station 420 is accomplished via the IR port 302 found on pager 50 and IR port 402 located on the docking station 420. When pager 50 is properly placed ("docked") within docking station 420, IR port 302 is properly aligned with IR port 402 in fairly close physical proximity (e.g., in this particular example less than one inch apart). The docking station 420 includes an internal IR transceiver circuit for transforming the information from RS- 232 format to an IR format for communication with pager 50. Information sent via the PC (not shown) to the pager 50 is sent via cable 404 and converted into IR by the internal IR transceiver found in the docking station 420. The IR is sent out via port 402 to port 302 which receives the IR information stream and provides the IR information to the internal IR circuitry 84 found in pager 50. Information sent from pager 50 to the PC travels in a reverse path to the information flow discussed above.

Referring now to FIG. 5, a detailed schematic of the IR circuit 84 located within the pager 50 is shown. The IR circuit 84 includes a conventional IR transceiver 510 such as an HSDL1001 IR transceiver manufactured by Hewlett-Packard, Inc. or other conventional IR transceivers manufactured by other manufacturers. IR transceiver 510 has built-in the IR receiver and transmitter. Data to be transmitted by pager 50 is sent via signal line 508 (labeled IRDA-TXD), the data to be transmitted is processed by controller 56 and sent via UART 118 to the IR transceiver 510 via the transmit signal line 508. A chip enable signal 512 (labeled IRDA_EN) is used to enable the IR transceiver 510, this signal is provided by controller 56.

IR signals received by the IR transceiver via IR port 302 are decoded by the IR transceiver 510 and sent to controller 56 via receive signal line 514 (labeled IRDA_RXD) and UART 118. In accordance with the present invention, when pager 50 is placed (docked) in docking station 420, a control signal is sent via controller 56 via line 506 (IN_CHARGER) to field-effect transistor (FET) 504. This signal is sent in response to controller 56 determining that the pager is properly docked in docking station 420 as previously mentioned above.

FET 504 acts as a power control circuit which controls the supply current to IR transceiver 510. The IR intensity emitted by IR transceiver 510 is determined by the current into the LEDA pin. By controlling the current into this pin, the IR light intensity of the transmitter is adapted (adjusted) to the current close physical proximity operating condition. In this specific case, the operating condition is that the IR transceivers which are communicating with each other are less than one inch away from each other, so very low IR intensity at either end is required to communicate. In one particular design example, if the voltage at line 502 (REG3V .MISC) is 3.0 volts and the voltage at LEDA is 2.5 volts, then the current at LEDA is determined by:

I_LEDA = (3-0 ^_ 2.5) /R, where R in the example shown in FIG. 5 is either 20 ohms or 20 ohms in parallel with 2.2 ohms.

The IN_CHARGER line 506 is used to control FET 504 which effectively switches the 2.2 ohm resistor in or out of the circuit.

CASE 1: Pager 50 is loaded into the docking station 420, controller 56 causes a high voltage state (e.g., 3.3. Volts) to appear on control line 506, this in turn causes FET 504 to turn off. So we have,

R = 20 ohms between the REG3V .MISC voltage supply line and input LEDA on transceiver 510, which gives a value for the current supplied of:

I_LEDA = (3.0 -2.5) /20 = 25 milliamp (mA).

CASE 2: Pager 50 is not loaded into the docking station 420, controller 56 causes a low voltage state (e.g., 0 volt) to appear on control line 506, this in turn causes FET 504 to turn on. So we have,

R = 1/(1/2.2 ohm + 1/20 ohm) = 1.98 ohm which gives,

I_LEDA = (3.0 V - 2.5 V)/1.98 = 250 mA.

The IN_CHARGER line 506 can be controlled by controller 56 as discussed above using control software stored in ROM 106, or can be implemented using other hardware circuitry which can sense when the pager is loaded in the docking station 420 as well as control the state of the voltage on line 506, depending on whether the pager is docked or not. Although in the preferred embodiment, a FET 504 is used as the power control circuit, other well known electrical designs can accomplish the same power cut- back needed for IR transceiver 510.

Sensing of the docking of the pager 50 as mentioned before can be accomplished using a number of well know techniques known in the art as previously discussed. The controller 56 upon determining that the pager 50 has been docked adjusts the voltage on the IN-CHARGER line 506 accordingly.

In FIG. 6, a flowchart highlighting the steps taken in the present invention are shown. After the routine is started, in step 604 it is determined if the electronic device 50 has been docked into the docking station 420. If the electronic device has been docked in docking station 420, controller 56 via one of its I/O ports which is coupled to one of the three charger contacts 412 (the sense line), receives a pull-down condition (or pull-up condition in an alternate design) on that port. This docked condition signal causes the controller 56 to send a high voltage signal via one of its output ports to the IN_CHARGER line 506. The high voltage signal causes the FET 506 to turn off, thereby cutting the amount of current supplied to IR transceiver 510. This causes the pager 50 to move from a first IR power level to a second and lower IR power level operating condition.

In step 608, the controller continues to monitor that the pager 50 is still in the charger by monitoring the charger's sense line via the select pager port 412 which indicates that the pager 50 is still docked. If it is determined in step 608 that pager 50 is no longer docked in the docking station 420, controller 56 places a logic low condition (0 volt) on the IN_CHARGER line 506. This causes the current supplied to the IR transceiver 510 to increase, which in turn causes the IR transmitter to transmit IR signals with greater intensity using the first IR power level (e.g., in order to conform to IrDA standard distance requirements, etc.). As discussed above, the present invention is very useful in situations where the electronic device 50 has to operate with an IR intensity (power) level which allows it to communicate with other remote devices up to a certain distance, maybe due to a standard requirement (IrDA, etc.), etc. But in situations, such as when the pager 50 is docked into its docking station 420 and is in close physical proximity to the docking station's IR transceiver, the ability to sense this proximity condition and automatically reduce the power level of the IR transceiver provides several advantages. Lower current drain by the device's IR transceiver 510 means lower IR intensity, which reduces the chance of IR distortion from occurring due to the close proximity of the IR transceivers. Lower current drain by the IR transceiver 510 will induce much less transmit noise on the pager's RF transmitter section and will also help reduce the amount of time the pager's battery 86 requires to charge when it is in the docking station 420.

The preferred embodiment as described above requires minimal changes and cost to a conventional IR transceiver circuit. By using a "sense signal" as provided by the docking station's charging circuit, or by use of another proximity sensor (e.g., mechanical switch, etc.) in the charging station 420 or in pager 50 itself, the pager's IR power output can be adjusted automatically upon being placed in close physical proximity to another device, in this case the docking station 420.

While the preferred embodiments of the invention have been illustrated and described, it will be clear that changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

What is claimed is:

Claims

1. A method for automatically adjusting the infrared power level of an electronic device's infrared transmitter, comprising the steps of: (a)- determining if the electronic device is in close physical proximity to an external device which the electronic device can communicate with using the electronic device's infrared transmitter; and

(b) reducing the power level of the electronic device's infrared transmitter automatically if it is determined that the electronic device is in close physical proximity to the external device.

2. A method as defined in claim 1, wherein step (b) comprises reducing the amount of current supplied to the infrared transmitter.

3. A method as defined in claim 1, further comprising the further step of:

(c) increasing the power level of the electronic device's infrared transmitter automatically back to the level it had before step (b) occurred once it is determined that the electronic device is no longer in close physical proximity to the external device.

4. A method as defined in claim 3, wherein the external device is a docking station which can receive the electronic device and step (a) comprises determining that the electronic device has been placed in the docking station.

5. A method as defined in claim 4, wherein the electronic device receives a signal from the docking station indicating that the electronic device has been docked in the docking station when the electronic device is placed in the docking station.

6. A method as defined in claim 5, wherein the electronic device in response to receiving the signal from the docking station automatically reduces the amount of current provided to the infrared transmitter.

7. A method as defined in claim 5, wherein the electronic device upon determining the signal is no longer being received from the docking station automatically increases the amount of current provided to the infrared transmitter to the level it was set at before the current to the infrared transmitter was reduced.

8. An electronic device which can communicate with an external device using infrared (IR) communications, comprising: an IR transmitter operable between a first and a second IR power level, the second IR power level being lower than the first IR power level; an input port for receiving a signal from the external device indicating that the electronic device is in close physical proximity to the external device; and a power control circuit in response to the signal being received at the input port automatically adjusts the IR transmitter to operate using the second IR power level.

9. An electronic device as defined in claim 8, wherein the power control circuit automatically adjusts the IR transmitter to operate using the first IR power level when the electronic device is no longer in close physical proximity to the external device.

10. An electronic device as defined in claim 8, wherein the electronic device is a communication device and the external device is a docking station which can receive the communication device.

11. An electronic device having an infrared circuit for communicating with a docking station which can accept the electronic device, the electronic device comprising: an infrared transmitter set at a first power level; and a controller coupled to the infrared transmitter, the controller automatically adjusts the infrared transmitter to operate at a second power level which is lower than the first power level when the electronic device is docked in the docking station.

12. An electronic device as defined in claim 11, wherein the controller adjusts the infrared transmitter to operate at the second power level by lowering the amount of current supplied to the infrared transmitter.

13. An electronic device as defined in claim 11, wherein the controller automatically adjusts the infrared transmitter to operate at the first power level when the electronic device is removed from the docking station.