CA2088046A1 - Transmission method for an infrared remote control system - Google Patents

Abstract

ABSTRACT
Transmission method for an infrared remote control system For the transmission of signals triggered by long key depressions from a transmitter to a receiver, repeat signals (R) are transmitted while the key is held down.
Releasing the key triggers a separate shift signal (S).
A burst-pause modulation method is used to transmit the repeat and shift signals (R) and (S).
Information units are defined here by different lengths of the burst intervals. The burst intervals and the burst packets are selected in such a way that infra-red transmitters with a linked power supply can be used.

(Figure 9)

Description

2~8~'~6 ;

Transmission method for an infrared remote control system FIELD OF THE INVENTION
The present invention relates to a transmis~ion method for an infrared remote control system for the transmission of data seguences or telegrams, trigyered by long and short key actuations on a keypad, between a transmitter and a receiver, where the different key depressions on the keypad are interpreted.

PRIOR ART
Pseudo-continuous operations, for example sequen-tial cycling through a series of discrete actuation values, are conventionally controlled during a key depression, for example in ~he case of a remote control-ler, by transmission of one con~and per step, or by the transmission of a few commands, the non-arrival o a command within a specific time being interpreted as the end of the key depression, or by the transmi sion of the beginning and end of the key depression.
So-called transmission protocols are used for the transmission of binary-coded data groups or data sequences, that is to say da~a which are represented by on and off states. In this case a station transmits such data sequences with the aid of high-frequency waves for example, and a receiving station evaluates the data sequences received, for which it must know the trans-mission protocol. The latter essentially defines the form ?,0880~i and the content of the transmitted data and only then i5 it possible for such data to be evaluated.
~ wide variety of su~h pro~ocols are known and are used throughou-t the data communications field. The large number of diferent protocols is primarily attributable to the variety of applications, such as data transmission of computer information or pure control information for e~uipment for example. In partîcular, data protec~ion, integrity and signaling ra~es are also the determining factors, which sometimes hinder one another. Th~ transmission medium must likewise be taken into account.
The object of the invention is ~o find a tran~-mission method which ensures a reliable transmission of a long key depre6sion with the smallast possible number o~ commands, the end o~ the key depre~sion being detected as preci~ely as possible, and which requires only a limited amount of power.

SUMMARY OF THE INVENTION
This object i9 achieved according to the inven-tion in that repeat signals R are repeatedly tr~nsmitted by the transmitter from the depre~sion until the release of the key on the keypad, the release of the key generat-ing a separate shift signal S and terminating the trans-mission of the repeat signals R, and in that a burst-pau~e modulation method is provided in the transmitter for the transmission of the repeat and shift signals R
and S, in which the num~er of burst periods per burst 2 ~

packet of the duration TB r and the burst intervals TAO, T~1... are selected in such a way that a storage means which provides the required power and voltage amplitude for the transmission is charged by means of a DC/DC
transformer during the pauses despite a power supply with low voltage and capacitance.
A preferred embodiment of the invention i9 one wherein a circuit is provided which interprets in the receiving device the non-appearance of a repeat command not as the end of the k~y depression but only as an interruption.
A further preferred embodimen-t of the invention i8 one wherein the Eirst repeat signal i~ transmitted after A key depre~sion longer than 400 milliseconds and i9 repeated at intervals of at most 1 second until the key is released~
A special preferred embodiment of the invention is one wherein a circuit is provided in the receiver, which circuit genexates a n~mber of discrete control ~ignals after receiving a repeat signal during at least one interval of the repeat signals.
By virtue of the transmission method according to the invention, p~eudo-continuous operations can be reliably controlled with the aid of a long key depress-ion, of several seconds for example, at the transmitting device. If the reception of the repeat signal is inter-rupted, the operation is not terminated, but merely interrupted, and can be continued once repeat signals are received again. As a result, for example in the case of 2n~0~6 a light control device, a dimming operation which is initiated and continued by means of a long key depress-ion, is not terminated due to the interruption of the send signal, for example as the result of a tamporary covering of the transmitter-receiver connectionr but is merely interrupted. ~s soon as further repeat signals are received, the dimming operation is continued in the original direction. In the case of a light control for example, when the key is released a shift signal is transmittad as a separate command. Said shift signal indicates the end of the curren~ operation, for example of the dimming operation illustrated. It is thus poss-ible r for example, to reverse the direct.ion of the dimming function, and tha next repeat signal~ raceived causo a dimming eEfect in the opposite direction to the original ona. Irhe preEerred embodi.ments oE the invention envisage the use of 16 periods per burst packet, and the pause interval being at least 10 times the length of the bursk packet.
A further prefarred emhodiment envisages that four different in~ormation units with four diffarent burst intervals are used, one information unit being used in each case to mark the beginning and the end of the data sequence and to represent the states O and 1.
By virtue of the method according to the inven-tion, it i5 possible to transmit telegrams or data sequencas reliably even with transmitters having a weak power supply. It is then possible for the transmitter to refresh its energy store during the burst in-tarvals in 3 4 ~

order to transmit the nex~ burst packat with suf~icient power. Thus, the energy store need no longer be dimen-sioned so large as to ensure an uninterrupted transmit-ting capacity. Energy s~ores with smaller dimensions are also noticeably smaller in their dimensions and weight than larger energy stores, which means recluced dimensions and smaller weight, and thus greater ease of operation, for hand-held transmit~ers in particular.

DESCRIPTION OF THE INVENTION
~n exemplary embodiment of the invention will be explained i.n greater detail below with reference to drawings, .in which:
Figure 1 show a block circuit diagram of the transmitter according to the invention, Figure 2 shows the total address range of the transmitter, Figure 3 shows the telegram structure of a tale-gram to be transmitted, Figure 4 shows the circuit diagram for the trans-mitter power supply, Figures 5, 6 show the PPM coding and the modulated PPM
signal of the tran~mitter, Figure 7 shows a block circui~ diagram of the receiver according to the invention, Figure 8 shows a block circuit diagram o the preamplifier, Figure 9 shows a diagram of the signal trans-mission depending on a long T key 2 ~

depression and the corresponding light con~rol, and Figure 10 shows a diagram of the signal trans-mission depending on a ~hort key depress-ion and the correspon~ing ON/OFF control.

DESCRIPTION OF THE PRI~FERRED EMBODIMENTS
Figure l 6hows the block circuit diagram of the transmitter 10. The transmitter 10 is for example an infrared transmitter for controlling various electrical consumers such as light fixtures, audio equipment and window blinds. The transmi~ter 10 comprises a keypad 12, a ~irst microprocessor or ASIC 14, a power supply 16, an address presetting means 18 and a transmitter ~tage 20"
When any key on the keypad 12 is pressed, the power supply 16 is activated by a first control signal Sl of the keypad 12 and e~tablisheA the supply voltage VS
requirad for the microprocessor or ASIC 14 and for driving the transmit diode D2 of -the transmitter stage 20. As soon as ~he power supply 16 has reached the required voltage, the microprocessor or ASI~ 14 starts up and assumes control of the power supply 16 with a second control signal S2. The output signal T5 of the keypad 12 is read in by the microprocessor or ASIC 14 and indicates which key on the keypad 12 was pre~sed.
The first control signal Sl and the second control signal S2 are assigned to a logic OR circuit 19, which generates a third control signal S3 which activates the power supply 16.

2 ~
- 7 _ The microprocessor or ASIC 14 then generates a ourth address contxol signal S~ with which the device address Al, A2, A3, ~4 ... set at the address presetting means 1~ with the aid o coding switches 22 is selected by a logic circuit 21.
The addresses are represented by eight address bits for example, the address space (see Fig. 2) being logically divided into four banks (2 bits) each with eight groups (3 bits) with eight device addresses (3 bits) each.
In each case one group address G can be set at the transmitter 10 with a coding switch 22, and four device addresses can be freely salected within said group. The bank address is hard-wired.
The transmission of aommands between the tran3-mitter 10 and the receiver of a control device is based on individual data sequ~nces or telegrams (one command is transmitted per telegram), in which the information i8 digitally encoded.
The telegram structure of a telegram is shown in Fig. 3. A telegram comprises:
- eight address bits ~ four data bit~
- four data pro~ection bits (CRC coding) - one start bit SOT (start of telegram) - one stop bit EOT (end of telegram).
The start bit SOT and the stop bit EOT are used for synchronization purposes, so that the beginning or the end of a telegram is clearly detected.

2 ~

Each key o the keypad 12 is assi~ned to exactly one of said device addresses. The device address spec-ified in ~he output signal A5 of the logic circuit 21 determines the three least significant bits of the address field in the telegram (Figure 3~. At the same time the group address G set with the coding swltch 22 is read in and determines the three most significant address bits of the telegram. The two most significant bi~s of the address fiald are filled with corresponding bank addresses. The four data bits are used to represent the corresponding commands in accordance with the length of the key depression on the keypad 12. The address and data ~ield thus generated is supplemented by the further bits or data protection (CRC coding) and the telegram (Fig.
3) is thus ormed.
The microprocessor 14 performs burst-pause modulation ~pulse position modulation and subsequent carrier frequency modulation), and generates a trans-mission control signal TM to drive a transmit amplifier 24 connected in series with ~he transmit diode D2.
Said transmit amplifier 24 generates the trans-mission current IS through the diode D2, which generates light signals in the infrared range in accordance with the current. Since the power supply cannot make suff:i-cient power available to generate the transmission current IS, a capacitor Cl is used to store the energy temporarilyl said capacitor being dimensioned such that a whole telegram can be transmitted with at least the current intensity IS.

2~3~
g ~ 9 soon as no further telegrams need be -trans-mitted as a result of the key depression (key released), the microprocessor or ASIC 14 deactivates the power supply 16 by means vf the second control signal S2, whereupon the power cons~mption can be reduced to a negligible ~alue in the standby mode.
The circuit of the power supply 16 is illustrated in Fig. 4.
Only a battery 26 with a low voltage ~1.5 volt cell) is used to supply power to the transmitter 10.
However, a higher voltage is required to drive the inrared transmit diode D2 and the microprocessor or ~SI:C
14. This is achieved in that connected downstream of the battery 26 i~ a magnetic DC~DC transfo.rmer 28 which transforms the low input voltage VB to a higher voltage level VS. A closed-loop control circuit 32 is acti~ated via the control input 30 of the third power supply control signal S3, with the result that a transistor Tl is switched on and a current IL begins to ~low through a coil L. A quantity of energy proportional to the current is stored in the coil L. If the transistor T1 is now switched off, the energy in the coil decays and flows of through a diode D4 into the capacitor C1, whereupon a voltage begins to become established across the capacitor Cl. Packets of energy are transferred into the capacitor Cl by repeatedly switching the transis-tor ~1 on and off, and the voltage is thus gradually built up. This is continued until the desired voltage VS has been estab-lished across the capacitor Cl. The closed-loop control 2 ~

circuit 32 determines that the desired voltage has been reached and terminates the period switching on and off of the transistor T1, to be precise until the control voltage UR falls below a predetermined value. The peri-odic switching on and off is generated by an oscillator, it also being possible to use the coil L as the frequency-determining component. The osc.llator is built into the closed-loop con~rol circuit 32.
When the infrared transmitter 10 is activated~
the voltage transformer 28 is set in operation. ~he voltaga of the battery 26 is thus transformed to the de~ired higher voltage level VS and is preerably stored as energy store in the capacitor Cl. After a de~ined period of time, the telegram to be transmitted is trans-mitted by means of the controlled transmit amplifier 24 and the in~rared diode D2l and the capacitor Cl is consequently partially discharged again. As a result it is possible to make do with, for example, a single 1.5 volt cell as the energy source. The IR transmitter 10 can -therefore be built smaller than hitherto/ or else ha~e more space available for the transmission electronics.
Alsol fewer batteries need bs exchanged.
The telegram ~ransmission method is illustrated diagrammatically in Figs. 5 and 6.
Only a limited power supply is a~ailable ~bat-tery/ 1.5 Vl type AAA) in the transmitter 10l 50 the transmission method must be selected such that the required range (approx. 20 m~ and the life (approx. 3 years under normal conditions of use) can be maintained 2 0 ~

for the battery 26.
The telegram is transmitted using a burs-t-pause modulation method. For this transmission, the individual bits are coded with a PPM method (pulse position modula-tion~ in the microprocessor 14 and are subsequen~ly modulated with a carrier frequency. With this type of coding the information carrier is the interval between two pulses (TA0, T~l, Fig. 5).
Overall four different intervals are used: EOT, "0", "1~' and SOT. Since the unmodulated PPM method is broadband, the individual pulses are modulated with a carrier frequency ~447.5 kHz), to be precise in such a way that 16 periods of the carrier frequency are trans-mitted per pul~e. Such a pulse packet is termed a burst with the burst length TB (32 us). The modulated PPM
signal (Fig. 6) i9 termed the BPM signal (burst position modulation). This coding and modulation method i8 very energy-saving since power is only consumed during the burst phases and the intervals between the bursts (TA0, TB, TA1-TB, etc.) can be used to refresh a temporary energy store at least par~ially, especially when the burst intervals are selected to be much longer than the burst length.

Stop bit EOT : 14*TB
Bit 0 : l9*TB
Bit 1 : 24*TB
Start bit SOT : 29*TB

- 1~ ~
A burst packe-t of the duration TB has r for example, 16 periods, that is ~o say 16 short flashes of light are transmi~ted by the IR transmit diode D2. After an interval of the duration T~O, a second burst packet is transmitted once more. The burst intervals TAO, TAl are selected so that the transmit~ar 10 has enough time, namely T~O-TB, to make the energy still missing available for the transmission of the following burst packet if it does not have a sufficient energy store constantly available. In this way transmitting devices with a weak energy source can be used to transmit such infrared signals, in that they do not transmit a weak signal continuously, but rather a stronger signal or a limited time, the burst. In particular the dimensions and the weight of the transmit~ing device can be consequent:Ly reduced since the energy source usually represents the heaviest and least flexible element in terms of its dimensions, particularly in hand-held transmitters.
The receiver 36 (Fig. 7) thus evaluates the burst intervals between the burst packets received in each case, detects the various telegrams, and forwards them to an evaluation circuit 38 in accordance with the above coding.
The receiver 36 comprises a receive diode Dl which converts infrared signals into current r and a preamplifier 40 whirh conditions the weak current signals received in such a way that they can be processed further by a downstream second microprocessor 42 of the evalu-ation circuit 38.

The infrared light signal (light burst packet) is converted into a current burst by the re~eive diode D1 in the receiver 36. ~ bandpass fil~er 44 (Fig. 8) can be used to filter said current burs-t, which bandpass ilter allows the bursts to pass ~t is able to damp sufficient-ly all ~he interference not in the range of the carriar frequency. Most of the interering frequencies in the infrared range are in the frequency range around 40 kHz (for example control gear, etc.3.
The preamplifier 40 (Fig. 8) is designed in such a way that the signals received are first filtered and then amplified. After the amplifîcation, the nu~ber of periods of the signal received is counted in a pulse counter 46 and, i~ the required n~mber o~ periods have been received, a single receive pulse S5 is Eorwarded to the second microproce~sor or ASIC 42, which then evalu~
ate~ the intervals between said pulses.
The evaluation circuit 33 of the receiver 36 furthermore contains two coding switches 48 for determin-ing the device address A1 (3 least significant bits) and the group address G ~3 most significant bits). The second microprocessor 42 reads in said addresses when a command telegram is received and compares the address field with the address set at the receiver 36. If the addresses match, the command is stored for further processing, otherwise it ls rejected. At the same time the command telegram is examined for faulty transmission with the aid of the data protection bits. The telegram is rejected if the received telegram is ~ound not to be 3K.

- l42~
The evalua-tion circuit 38 also contains a memory (RAM~EEPRO~) or storing sta-tes for driving -the control unit 52. The microprocessor 42 is notified via so-called ~OD~ inputs which type is to be driven by the control unit 52, whereupon it then calls up the corre-sponding program in the program memory 54 (ROM). It i~
thu~ possible to ~enerate a plurality of different control signals S~ for various control units 52 (for example generaliæed phase control, relay, etc.) with a single microprocessor 42, to be precise depending on the MODE inputs.
Figure 9 shows a diagram for the transmitter transmission of a long key depression with infrared transmission o the telegrams using a limited pow~r supply in the transmit~ing device or driving continuous and pseudo-continuous operation~ with only one key.
A key ~or example Tl) i~ pressed on the koypad 12 of the transmitter 10 at the time TD and is released again at the later time TE, as is illustrated in thP
upper diagram in Fig. 9.
If the key depression lasts longer than TW (TW is 400 ms), then the key depression is interpret~d as "long", and from this time repeat signals R (or HOLD
commands) are transmitted with the interval TR from the first (microprocessor 42) until the key is released at the time TE. In this connection, a shift signal S (or TOGG~E command) is sent by the microprocessor 42, and the transmission of the repeat signals R is terminated. At the same time the release of the key causes a reversal of 29~0~

direction for-the control variable. A long key depression can be used, for example, to control a pseudo-continuous operation in such a way that the output control signal S7 of the control unit 52 of ~-he receiver 36 is altared by a small amount delta S in small time steps delta T, such as the dimming of l~ninaires or example.
Owing to the limited power supp:Ly (battery) in the transmitter 10, the interval ~R of the repeat signals must be selected to be sufficiently long (due to power consumption and hence increased life of the battery), but on the other hand it is to be possible for the receiver 36 to detect the end of the key depression as precisely as possible in order, when dimming or example, to be able to set the final value as precisely as possible. For this purpose, the shift signal S is transmitted when the key is released and the recelver 36 interprets this as the end of the key depression. It is thuæ possible to select a long interval TR between the repeat commands (800 ms). The time steps dalta T ~or the control variable are short (approx. 60 ms) in relation to the interval between the repeat commands R, but the final value can nevertheles~ be set precisely because the shift signal is transmitted immediately the key is released.
An error in the transmission of the repeat signal R is not interpreted in the receiver 36 as the end of the key depression, which would indeed also result in a change of direction~ but as an interruption, the duration TT until the detection of the interruption being selected to be longer than the duration of the interval TR of the 2~0~
_ 16 -repea~ commands R (TT: 1~). If such an interrup-tion is determined at time TU, the control signal S7 is not changed un~il a repeat signal R i~ received again, no change of direction being indicated in this case. The non-~ppearance of ~he concludiny shif~ signal S is interpreted a~ an interruption, that i~ to ~ay a subse-quent long key depres~ion at the tra]nsmitter 10 is interpreted in the receiver 36 as the resumption of the original key depression.
Fig. 10 shows the diagram of ~he transmitter transmission for a short key deprsssion which las~s less than 400 ms. ~ shift signal S i~ transmitted by the microprocessor or ASIC 14 which switches the receiver 36 ON or OFF depending in each case on whe~her the current state was OFF or ON respectively.
The HOLD function is used to e~tablish a logical connection b~tween transmi-tter 10 and receiver 36, and ser~es for the transmis~ion of a long key depression > 40~ ms)-A short key depression generates a shift signalS or shift telegram, a long key deprQssion generates repeat signals R or repeat telegrams, followed by a shift telegram S when the key is released.

Claims (7)

1. PATENT CLAIMS
   
   l. A transmission method for an infrared remote control system for the transmission of data sequences or telegrams, triggered by long and short key actuations on a keypad (12), between a transmitter (10) and a receiver (36), where the different key depressions on the keypad (12) are interpreted, wherein repeat signals (R) are repeatedly transmitted by the transmitter (10) from the depression until the release of the key on the keypad (12), the release of the key generating a separate shift signal (S) and terminating the transmission of the repeat signals (R), and wherein a burst-pause modulation method is provided in the transmitter (10) for the transmission of the repeat and shift signals (R) and (S), in which the number of burst periods per burst packet of the duration TB, and the burst intervals TA0, TA1... are selected in such a way that a storage means which provides the required power and voltage amplitude for the transmission is charged by means of a DC/DC transformer (28) during said pauses despite a power supply (26) with low voltage and capacitance.
2. 2. The transmission method as claimed in claim 1, wherein a circuit is provided which interprets in the receiver (36) the non-appearance of a repeat signal (R), which is transmitted after a depression longer than 400 milliseconds and is repeated at intervals of at most 1 second until the key is released, not as the end of the key depression but as an interruption.
3. 3. The transmission method as claimed in claim 1, wherein 16 periods per burst packet are used, four different information units with four different burst intervals being required in order to have one information unit available in each case to mark the beginning and the end of the data sequence and to represent the states O
   and 1, and wherein the burst interval is at least 10 times the length of the burst packet.
4. 4. The transmission method as claimed in claim 1, wherein the voltage transformer required to generate the transmitting power is a magnetic transformer, connected downstream of which is a capacitor (C1) for temporarily storing the energy.
5. 5. The transmission method as claimed in claim 1, wherein the receiver (36) generates a number of discrete control signals (S7) after receiving a repeat signal (R) during at least the interval of the repeat signals.
6. 6. A data transmission system between an infrared transmitter (10) and an infrared receiver 136), in which the transmitter (10) contains a keypad (12) with an address presetting means (18) and at least one transmit diode (D2), wherein there is provided in the transmitter (10) a microprocessor or ASIC (14) which performs a PPM
   coding and a subsequent carrier frequency modulation in order to generate a transmission control signal (TM) which is required to drive a transmit amplifier (24) connected in series with at least one transmit diode (D2), and wherein the microprocessor or ASIC (14) deactivates the power supply (16) of the transmitter (10) when the key is released.
7. 7. The data transmission system as claimed in claim 6, wherein the receiver (36) contains at least one receive diode (D1), which is driven by a microprocessor or ASIC (42) in such a way that the received pulses or burst packets of the receive diode (D1) are filtered and formed in a preamplifier (40), and wherein the micropro-cessor or ASIC (42) evaluates the intervals between the pulses in order to detect the various telegrams.