CN112398562B - Clock synchronization method for transmitting analog signal waveform by using digital signal - Google Patents
Clock synchronization method for transmitting analog signal waveform by using digital signal Download PDFInfo
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- CN112398562B CN112398562B CN202011079257.2A CN202011079257A CN112398562B CN 112398562 B CN112398562 B CN 112398562B CN 202011079257 A CN202011079257 A CN 202011079257A CN 112398562 B CN112398562 B CN 112398562B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0602—Systems characterised by the synchronising information used
- H04J3/0605—Special codes used as synchronising signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/24—Time-division multiplex systems in which the allocation is indicated by an address the different channels being transmitted sequentially
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0078—Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location
- H04L1/0083—Formatting with frames or packets; Protocol or part of protocol for error control
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Abstract
The invention discloses a clock synchronization method for transmitting analog signal waveform by using digital signal, comprising the following steps: starting a timer of the main sensor, starting the main sensor to transmit data, and calling the rest sensors as slave sensors; each slave sensor receives data sent by the master sensor, starts a timer of the slave sensor after finishing receiving the data of the master sensor, and then determines a time slot for each slave sensor to transmit the data by using the timer of the slave sensor; the sensor signal receiving end receives the data of each sensor and puts the data into a buffer, the data is read out from the corresponding buffer area of the buffer under the control of a digital-to-analog conversion clock corresponding to the sensor, and then the received data is restored into an analog waveform through a digital-to-analog conversion circuit. The invention realizes the transmission of analog waveforms and the synchronization of each sensor and the synchronization of analog-digital conversion and digital-analog conversion clocks in the waveform transmission process by utilizing a wireless digital communication mode.
Description
Technical Field
The invention relates to the technical field of communication transmission synchronization, in particular to a clock synchronization method for transmitting analog signal waveforms by using digital signals.
Background
In the conventional remote automatic control system and the remote measuring system (as shown in fig. 1), the signals collected by the sensors are transmitted to the central control unit in an analog signal manner through cables or radio waves. Due to electromagnetic interference in the nature and the influence of cable transmission characteristics, sensor signals are distorted more or less in the transmission process, in a control system, the control precision of the system and even the stability of the system cannot be guaranteed, and in a measurement system, due to the influence of interference and distortion, the measurement precision is influenced by errors generated in the transmission process.
In order to reduce the influence of disturbances on the sensor measurement signal, sensors for remote measurement usually employ a current signal. Although the anti-interference capability of the current signal is higher than that of the voltage signal, the signal is still affected by thermal noise and various interferences, and the trouble that the sensor needs to be powered exists, especially in the use scenes such as oil drilling and coal mining, and the requirement on power supply is very strict due to the requirement on safe production.
It is desirable to convert the measurement signal to a digital signal at the sensor end and send the measurement result in the form of a digital quantity to the central control unit. In a practical system, there are a large number of central control units that require input signals to be analog signals, which requires that digital signals are converted into analog quantities at a receiving end through a digital-to-analog conversion circuit, and then the analog signals are input to the central control units.
In order to solve the interference problem of the sensor measurement data in the transmission process, a method for realizing the transmission of the analog waveform and the synchronization of each sensor and the analog-to-digital conversion and the synchronization of the digital-to-analog conversion clock in the waveform transmission process by using a wireless digital communication mode is urgently needed.
Disclosure of Invention
The present invention is directed to solve the above-mentioned drawbacks of the prior art, and provides a clock synchronization method for transmitting analog signal waveforms using digital signals.
The purpose of the invention can be achieved by adopting the following technical scheme:
a clock synchronization method for transmitting analog signal waveform by using digital signal is applied to a remote automatic control system or a remote measurement system, the remote automatic control system or the remote measurement system comprises a plurality of sensors for remote measurement and sensor signal receiving ends, the clock synchronization method divides signal transmission time into M time slots, all M time slots form a frame, wherein the first time slot is a main time slot, a sensor for transmitting data in the main time slot is a main sensor, the main sensor comprises a timer for controlling the synchronization of each sensor, which is called as a main sensor timer, each sensor acquires signals, and the signals to be acquired are transmitted to the sensor signal receiving ends in a time slot allocated to the sensor after the number of the signals to be acquired is equal to or exceeds one frame, the clock synchronization method comprises the following steps:
s1, starting a timer of the main sensor, starting the main sensor to transmit data, and calling the rest sensors as slave sensors;
s2, each slave sensor receives the data sent by the master sensor, the slave sensor starts the own timer of the slave sensor after finishing receiving the data of the master sensor, and then the own timer of the slave sensor is utilized to determine the time slot of each slave sensor for transmitting the data;
s3, a sensor signal receiving end receives each sensor data and puts in a buffer, under the control of a digital-to-analog conversion clock corresponding to the sensor, the data is read out from a buffer area corresponding to the buffer, then the received data is restored into an analog waveform through a digital-to-analog conversion circuit, wherein the sensor signal receiving end comprises a timer with the length equal to the frame length, the working mode of the timer of the sensor signal receiving end is the same as that of a main sensor timer, the timing of the next frame is started automatically after the timer is finished, and when each frame is finished, the position of the data in the digital-to-analog conversion reading buffer is adjusted through the difference between the number of the received data in one frame and the number of the data which are subjected to digital-to-analog conversion by the sensor signal receiving end, so that the synchronization of the analog-to-digital conversion clock and the digital-to-analog conversion clock is realized.
Further, in step S3, the sensor signal receiving end adjusts the position of the data in the digital-to-analog conversion reading buffer by the difference between the number of the received data in a frame and the number of the data that has undergone digital-to-analog conversion, so as to synchronize the analog-to-digital conversion clock and the digital-to-analog conversion clock, and the process is as follows:
assuming that the number of measured digital quantities of the Nth sensor received by a sensor signal receiving end at the beginning of the Mth frame is mReceive, at the end of the frame, reading mSend digital quantities from a buffer by a digital-to-analog conversion clock, wherein the difference between the mSend digital quantities is as follows: and a deltaIndex-mResive-mSend, at the end of the frame, reading the digital-to-analog conversion clock used for the Nth sensor analog waveform recovery from the mIndex of the buffer and sending the data used for digital-to-analog conversion, and from the next frame, adjusting the position of the digital-to-analog conversion clock reading the data from the buffer as follows: and mIndex +1+ deltaIndex, wherein the deltaIndex value can be positive or negative, and after the reading position is adjusted, the number of data which are sent and used for digital-to-analog conversion is modified as follows: mSend ═ mReceive.
Further, the sensor transmits to the sensor signal receiving end through the wireless transmitter together with the address of the sensor during the period of time assigned to the sensor.
Further, after the sensor signal receiving end receives the sensor data, the sensor corresponding to the signal is distinguished through the address, and then the received data is stored in the buffer area corresponding to the sensor.
Further, in step S2, each slave sensor starts to transmit data when its own timer expires.
Furthermore, the timing lengths of the sensor timers are different, and the transmission time and the length of the occupied time slot of each sensor are further determined by setting the timing lengths of the sensor timers.
Further, the main sensor timer and the sensor signal receiving end timer automatically start new timing after the timing is finished, the rest timers stop running after the timing is finished, and the next timing operation is started only after new main sensor data are received.
Compared with the prior art, the invention has the following advantages and effects:
the invention discloses a clock synchronization method for transmitting analog signal waveforms by using digital signals, and provides a method for realizing the transmission of analog waveforms and the synchronization of each sensor and the synchronization of analog-to-digital conversion and digital-to-analog conversion clocks in the waveform transmission process by using a wireless digital communication mode. Compared with a common handshake communication mode, the sender and the receiver can only transmit information point to point, and in the scheme, the sensor sends data in a broadcasting mode, and can adopt a plurality of receiving terminals to receive information simultaneously, so that the communication efficiency is improved. Compared with a system which does not use a clock synchronization method, the system has the advantages that the signal changes of the sensors are synchronous, and the system is crucial to a system which needs a plurality of sensor data for correlation processing.
Drawings
FIG. 1 is a diagram illustrating measurement data transmission in a conventional sensor network;
FIG. 2 is a schematic diagram of an embodiment of the present invention for implementing analog waveform transmission using digital communication;
FIG. 3 is a time slot division diagram for implementing analog waveform transmission using digital communication in an embodiment of the present invention;
fig. 4 is a schematic diagram of a wireless transceiving system in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Examples
The embodiment provides a synchronization method between sensors and a clock synchronization method for analog-to-digital conversion and digital-to-analog conversion when digital signals are used for transmitting analog waveforms, and the synchronization method is suitable for half-duplex, half-duplex or full-duplex wireless digital channels.
To realize the transmission of a plurality of analog waveforms by using digital signals, synchronization between the sensors is ensured, otherwise, data communication between the sensors and the receiving unit cannot be performed. In order to ensure correct transmission of the analog waveform, the sampling clock for analog-to-digital conversion and the sampling clock for digital-to-analog conversion must be synchronized, otherwise the analog waveform is distorted, and measurement errors occur.
In order to avoid signal distortion caused by interference and line characteristics during transmission of the sensor, the present embodiment proposes a method for implementing analog waveform transmission by using digital signals. The method comprises a transmitting process and a receiving process, wherein the transmitting process comprises the following steps: the method comprises the following steps of sensor data acquisition, signal conditioning, analog-to-digital conversion, data caching, central control processing and wireless transmitter data transmission, wherein the receiving process comprises the following steps: the wireless receiver comprises a wireless receiver, a data receiving part, a data caching part, a central control processing part, a clock synchronization part, a digital-to-analog conversion part, a signal caching amplification part, a control execution part and the like, and the structure of the wireless receiver is shown in figure 2.
After the signals collected by the sensor are amplified and conditioned, the signals are converted into digital signals by an analog-to-digital conversion circuit, the collected digital signals are stored by a buffer, the signals to be collected are delivered to a controller after the number of the signals to be collected is equal to or more than one frame number, and the signals are transmitted to a sensor signal receiving end through a wireless transmitter and the address of the sensor in a time period allocated to the sensor.
At a sensor signal receiving end, after receiving data, the wireless receiver identifies the sensor corresponding to the signal through an address, and then stores the received data in a buffer area corresponding to the sensor. Under the control of a digital-to-analog conversion clock corresponding to the sensor, data is read out from a corresponding buffer area of the buffer, and then the received data is restored to an analog waveform through a digital-to-analog conversion circuit.
The following describes the synchronization method of the various sensors using a single communication frequency:
in order to ensure that the receiving end of the sensor signal can receive multiple sensor signals at the same time, the sensors need to work cooperatively, and for this purpose, the signal transmission time is divided into M time slots (as shown in fig. 3), wherein the first time slot is a main time slot, and all the time slots form a frame. In fig. 4, a wireless transceiver system with 5-way sensors and 1-way data processor is shown.
The pressure sensor is a main sensor, transmits data in a main time slot, a single chip microcomputer MCU used for collecting data is arranged in the pressure sensor, and a timer in the single chip microcomputer is used for controlling the synchronization of all the sensors. The length of the timer is equal to the length of time that all sensors send a frame of data, and in this example, the length of the timer is set to 2.5 seconds, which is determined by dividing the data bits of a frame by the transmission rate of the wireless signal system.
After the timer of the pressure sensor is started, the internal wireless module starts to transmit data, the data is transmitted in a broadcasting mode, and all wireless receivers in the same frequency band can receive the transmitted signals. Each of the remaining sensors in the system is a slave sensor that starts its own timer after completing receiving the master sensor data. The sensor timers have different timing lengths, and the length determines the transmission time of data. In the system, the pressure sensor data is sent after 1.2 seconds, the timers of other sensors start to work, the timing of hooking the sensor is 0 second, the timing of pumping the sensor is 0.2 second, the timing of the well depth sensor is 0.8 second, and the timing of sitting the card sensor is 1.0 second. And starting the sending module to send the measurement data after the timing time is up. The main sensor timer automatically starts new timing after the timing is finished, the rest timers stop running after the timing is finished, and the next timing operation is started only after new main sensor data are received. The length of each sensor timer is set, so that the sending time of each sensor and the length of the occupied time slot are determined.
The following describes a synchronization method of analog-to-digital and digital-to-analog conversion clocks at the signal receiving ends of each sensor and the sensor:
to ensure that the analog signal waveform recovered by the sensor signal receiving end is consistent with the waveform generated by the sensor, the digital-to-analog conversion clock of the sensor signal receiving end and the analog-to-digital conversion clock of each sensor transmitting end must be synchronous. Because the digital signal in the communication process only contains the clock information necessary for the communication circuit and does not contain the clock information of digital-to-analog conversion, the digital-to-analog conversion clock necessary for the signal receiving end of the sensor cannot be generated through the clock recovery circuit. To this end, the present embodiment discloses a clock synchronization method when transmitting an analog signal waveform using a digital signal.
The clock synchronization method utilizes the number of the received digital signals to synchronize a digital-to-analog conversion clock and an analog-to-digital conversion clock. The sensor signal receiving end is provided with a timer with the length equal to the frame length, the working mode of the timer at the sensor signal receiving end is the same as that of the main sensor timer, and the timing of the next frame is automatically started after the timer is finished. When each frame is finished, the signal receiving end of the sensor adjusts the digital-to-analog conversion clock, and the specific process is as follows:
assuming that the number of measured digital quantities of the Nth sensor received by a sensor signal receiving end at the beginning of the Mth frame is mReceive, at the end of the frame, reading mSend digital quantities from a buffer by a digital-to-analog conversion clock, wherein the difference between the mSend digital quantities is as follows:
deltaIndex＝mReceive-mSend
at the end of the frame, the digital-to-analog conversion clock for the nth sensor analog waveform recovery is read from the mldex of the buffer and sent as data for digital-to-analog conversion, and then starting from the next frame, the position at which the digital-to-analog conversion clock reads data from the buffer is adjusted as follows:
mIndex+1+deltaIndex
wherein, the deltaIndex value can be positive or negative. After the reading position is adjusted, the number of data sent for digital-to-analog conversion is modified as follows:
mSend＝mReceive。
the above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (7)
1. A clock synchronization method for transmitting analog signal waveform by using digital signal is applied to remote automatic control system or remote measurement system, the remote automatic control system or the remote measuring system comprises a plurality of sensors for remote measurement and sensor signal receiving ends, the clock synchronization method divides a signal transmission time into M time slots, all of which constitute one frame, wherein, the first time slot is a main time slot, the sensor for transmitting data in the main time slot is a main sensor, the main sensor comprises a timer for controlling the synchronization of each sensor, which is called as a main sensor timer, each sensor collects signals, after the number of the signals to be collected is equal to or exceeds one frame, transmitting to a sensor signal receiving end during a time period allocated to the sensor, characterized in that the clock synchronization method comprises the steps of:
s1, starting a timer of the main sensor, starting the main sensor to transmit data, and calling the rest sensors as slave sensors;
s2, each slave sensor receives the data sent by the master sensor, the slave sensor starts the own timer of the slave sensor after finishing receiving the data of the master sensor, and then the own timer of the slave sensor is utilized to determine the time slot of each slave sensor for transmitting the data;
s3, a sensor signal receiving end receives each sensor data and puts in a buffer, under the control of a digital-to-analog conversion clock corresponding to the sensor, the data is read out from a buffer area corresponding to the buffer, then the received data is restored into an analog waveform through a digital-to-analog conversion circuit, wherein the sensor signal receiving end comprises a timer with the length equal to the frame length, the working mode of the timer of the sensor signal receiving end is the same as that of a main sensor timer, the timing of the next frame is started automatically after the timer is finished, and when each frame is finished, the position of the data in the digital-to-analog conversion reading buffer is adjusted through the difference between the number of the received data in one frame and the number of the data which are subjected to digital-to-analog conversion by the sensor signal receiving end, so that the synchronization of the analog-to-digital conversion clock and the digital-to-analog conversion clock is realized.
2. The method according to claim 1, wherein the sensor signal receiving end in step S3 adjusts the position of the data in the digital-to-analog conversion read buffer by the difference between the number of received data in a frame and the number of data that has undergone digital-to-analog conversion, so as to synchronize the analog-to-digital conversion clock with the digital-to-analog conversion clock, and the method comprises the following steps:
assuming that the number of measured digital quantities of the Nth sensor received by the sensor signal receiving end at the beginning of the Mth frame is mReceive, at the end of the frame, the digital-to-analog conversion clock reads the mSend digital quantities from the buffer, and the difference between the mSend digital quantities and the mSend digital quantities is: and a deltaIndex-mResive-mSend, at the end of the frame, reading the digital-to-analog conversion clock used for the Nth sensor analog waveform recovery from the mIndex of the buffer and sending the data used for digital-to-analog conversion, and from the next frame, adjusting the position of the digital-to-analog conversion clock reading the data from the buffer as follows: and mIndex +1+ deltaIndex, wherein the deltaIndex value can be positive or negative, and after the reading position is adjusted, the number of data which are sent and used for digital-to-analog conversion is modified as follows: mSend ═ mReceive.
3. A method of clock synchronization in transmitting analog signal waveforms using digital signals as claimed in claim 1, wherein the sensor is transmitted to the sensor signal receiving end by the wireless transmitter together with the address of the sensor during the time period allocated to the sensor.
4. The method of claim 3, wherein the sensor data received at the sensor signal receiving end is identified by an address, and the received data is stored in a buffer corresponding to the sensor.
5. The method of claim 1, wherein in step S2, each slave sensor starts sending data when its own timer expires.
6. The method of claim 1, wherein the sensor timers have different timing lengths, and the transmission time and the occupied time slot length of each sensor are determined by setting the timing lengths of the sensor timers.
7. The method of claim 1, wherein the master sensor timer and the sensor signal receiving end timer automatically start a new timing after the timing is over, the remaining timers stop running after the timing is over, and the next timing operation is started only after new master sensor data is received.
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| EP0498022A2 (en) * | 1991-01-28 | 1992-08-12 | Industrial Technology Research Institute | Timing recovery method and system for a receiver with A/D conversion |
| CN101714959A (en) * | 2008-12-30 | 2010-05-26 | 南京师范大学 | Analog/digital signal compound transfer transmitter and receiver |
| WO2014155956A1 (en) * | 2013-03-29 | 2014-10-02 | パナソニック株式会社 | Sensor unit, power measurement unit, and power measurement system |
| CN109286460A (en) * | 2017-07-21 | 2019-01-29 | 北京智云芯科技有限公司 | A kind of method for synchronizing time and system based on wireless communication |
| CN109996325A (en) * | 2019-01-28 | 2019-07-09 | 上海无线通信研究中心 | A kind of clock system and method for wireless sensor network |
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| EP0498022A2 (en) * | 1991-01-28 | 1992-08-12 | Industrial Technology Research Institute | Timing recovery method and system for a receiver with A/D conversion |
| CN101714959A (en) * | 2008-12-30 | 2010-05-26 | 南京师范大学 | Analog/digital signal compound transfer transmitter and receiver |
| WO2014155956A1 (en) * | 2013-03-29 | 2014-10-02 | パナソニック株式会社 | Sensor unit, power measurement unit, and power measurement system |
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| CN109996325A (en) * | 2019-01-28 | 2019-07-09 | 上海无线通信研究中心 | A kind of clock system and method for wireless sensor network |
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