Bus-addressed four-wire cascaded long-distance microphone selection acquisition system

Abstract

The present invention provides a bus-addressed four-wire cascaded long-distance microphone gating acquisition system, comprising: an edge processing module for generating and sending a return-to-zero code control signal containing a self-test mode code or a polling mode code; a plurality of gating acquisition modules serially cascaded via a four-wire bus; each of the gating acquisition modules is composed of a pure hardware circuit without a computing unit, comprising: a return-to-zero code chip for receiving the return-to-zero code control signal and transmitting it step by step to the next-level gating acquisition module, and outputting a control signal to an analog switch; an analog switch array for switching paths according to the control signal of the return-to-zero code chip, gating a microphone or a self-test signal; a relay amplifier chip for following and amplifying an audio signal to compensate for long-distance transmission attenuation; the edge processing module is configured with only one analog-to-digital converter, and time-sharing acquisition of audio signals of all cascaded gating acquisition modules is achieved by time-sharing gating the analog switch.

Description

Technical Field

[0001] The present invention belongs to the technical field of application system design of sound-to-electricity conversion equipment (microphone), and in particular relates to a bus-addressable four-wire cascaded long-distance microphone gating acquisition system. Background Art

[0002] In industrial scenarios such as mines, power plants, and ports, in order to ensure the stable operation of long-distance belt conveyor systems, it is necessary to monitor the operating status of belt rollers and other related components through multi-point sound collection and recognition technology. Figure 1 As shown in the figure, the current multi-point sound collection system adopts a tree-like forest structure and consists of multiple processing nodes. Each node contains an AI edge processing device and a limited number of collection pickups. The pickup is responsible for collecting audio signals and transmitting them for processing. However, the current monitoring solution has certain drawbacks. First, the tree-like topology collection system is difficult to wire in a complex industrial equipment environment, and it is difficult to flexibly adjust the wiring method according to the monitoring sample collection requirements. Secondly, since each node processes a limited number of pickup signals, multiple AI edge processing devices need to be configured, which leads to redundancy in equipment resources, thereby significantly increasing system costs. Finally, considering the impact of dust and vibration on the long-term reliability of pickups and edge devices, edge systems using multiple complex computing chips are difficult to maintain.

[0003] Figure 1 The implementation difficulties of the corresponding tree topology + parallel computing solution include:

[0004] Wiring issues in tree topology;

[0005] Too few fault samples;

[0006] Interference from different ambient sounds;

[0007] Multi-point voice is transmitted back in real time;

[0008] The effects of dust and vibration on the long-term reliability of pickups and edge devices. Summary of the Invention

[0009] In view of the defects and shortcomings of the tree-topology microphone acquisition system in the prior art, such as complex wiring, equipment redundancy (requiring multiple edge processing devices), and high maintenance difficulty (multiple computing chips are affected by dust and vibration), the present invention provides a bus-addressed four-wire cascaded long-distance microphone selection acquisition system.

[0010] The present invention achieves a technological breakthrough through the following innovative designs: using a serial bus cascade topology to replace the traditional tree structure, and realizing long-distance flexible wiring through a four-wire bus (power positive / negative, control line, audio line); designing a pure hardware selection acquisition module (without MCU and other computing units), which is composed of a return-to-zero code chip (such as SM16703P), a low on-resistance analog switch (such as TS5A3359DCUR) and a low-noise relay amplifier (such as OPA2335AID). The control signal is transmitted step by step through the return-to-zero code protocol, without the need for node handshaking or software programming, and supports theoretically unlimited levels. cascade; innovative dynamic address allocation mechanism (addresses are automatically determined by access sequence and detected through self-test mode) enables flexible replacement and expansion of modules; only a single AD converter is configured, and audio acquisition of all cascaded nodes is completed through time-sharing selection of analog switches, significantly reducing equipment cost and redundancy; combined with anti-interference designs such as shielded twisted pair cables, common-mode filter capacitors and differential input and output modules, it ensures the integrity of long-distance (200-meter cascade) audio signals; supports self-test and polling dual-mode operation (self-test mode detects valid nodes, polling mode time-sharing acquisition), improving system reliability and monitoring efficiency.

[0011] The present invention effectively solves the wiring, cost and maintenance problems of the microphone acquisition system in industrial long-distance belt monitoring scenarios, and has the advantages of high scalability, low redundancy and strong reliability.

[0012] The technical solution specifically adopted by the present invention to solve the technical problem is:

[0013] A bus-addressable four-wire cascaded long-distance microphone gating acquisition system, comprising:

[0014] An edge processing module, configured to generate and send a return-to-zero code control signal including a self-test mode code or a polling mode code;

[0015] Several strobe acquisition modules are serially cascaded via a four-wire bus, wherein the four-wire bus includes a positive power line, a negative power line, a control line, and an audio line;

[0016] Each of the strobe acquisition modules is composed of a pure hardware circuit without a computing unit, and the pure hardware circuit includes:

[0017] A return-to-zero code chip is used to receive the return-to-zero code control signal and transmit it step by step to the next-level strobe acquisition module, and output the control signal to the analog switch;

[0018] An analog switch array, used for switching paths according to the control signal of the return-to-zero code chip, and selecting a microphone or a self-test signal;

[0019] Relay amplifier chip, used to follow and amplify audio signals to compensate for long-distance transmission attenuation;

[0020] The edge processing module is configured with only one analog-to-digital converter, and realizes time-sharing acquisition of audio signals of all cascaded acquisition modules by time-sharing gating the analog switch.

[0021] Furthermore, the address of the strobe acquisition module is automatically determined by the access sequence, the address of the first strobe acquisition module accessed is 0, and the addresses of the subsequent strobe acquisition modules accessed are incremented in sequence, and the address information is dynamically detected and acquired through the self-test mode.

[0022] Furthermore, the code length of the return-to-zero code control signal is 24 bits, wherein:

[0023] The self-test mode code includes a first group of control bits, a second group of reserved bits, and a switchable third group of self-test signal bits for selecting the module to generate a self-test signal; the self-test signal bits are alternating level bits used to generate a test audio signal;

[0024] The polling mode code includes a first group of reserved bits, a second group of control bits for switching the strobe module to the microphone acquisition path, and a third group of reserved bits.

[0025] Furthermore, the relay amplifier chip is a low-noise operational amplifier, which is used to compensate for signal attenuation during long-distance transmission, so that the audio signal amplitude loss is controllable when the cascade transmission distance is not less than 200 meters.

[0026] Furthermore, the strobe acquisition module also includes a microphone preamplifier circuit composed of an operational amplifier, a resistor voltage divider network and a negative feedback resistor, and the output audio signal amplitude is made lower than 1.2V by adjusting the negative feedback resistor.

[0027] Furthermore, each cascade module of the power positive line is independently provided with a self-recovery fuse, which is used to automatically disconnect the lower-level power supply when a short circuit or overload occurs in the cascade module.

[0028] Furthermore, the audio line adopts a shielded twisted pair, and the cascade interface is configured with a common-mode filter capacitor, or connected to a differential input and output module to suppress external coupling voltage interference.

[0029] Furthermore, the edge processing module supports two operating modes:

[0030] Self-test mode: dynamically detect the number of valid strobe acquisition modules by sending self-test mode code;

[0031] Polling mode, sending a polling mode code according to the effective number, selecting the microphone node by node to collect audio signals;

[0032] Among them, the self-test mode takes precedence over the polling mode.

[0033] Furthermore, the strobe acquisition module adopts a detachable cascade structure, which supports dynamic increase or decrease in the number of modules.

[0034] Furthermore, the output amplitude of the preamplifier circuit is adjusted to 1V, so that the noise amplitude is relatively reduced.

[0035] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects:

[0036] First, by replacing the traditional tree structure with a serial bus cascade topology, the problem of difficult wiring in complex industrial scenarios is solved, supporting flexible arrangement of pickup points over long distances, greatly improving the convenience of system installation and maintenance; second, a pure hardware-gated acquisition module (without MCU or other computing units) is used in combination with a return-to-zero code control protocol to achieve step-by-step transmission and hardware gating of control signals, avoiding handshakes or software programming between nodes, significantly improving the system response speed and long-term operation reliability; finally, through a single AD time-sharing acquisition mechanism, only one analog-to-digital converter is required to complete audio acquisition of all cascaded nodes, effectively reducing equipment redundancy, hardware costs and maintenance difficulty.

[0037] The dynamic address allocation mechanism (the address is automatically determined by the access sequence and detected through the self-test mode) avoids the tedious operation of physical or software address setting and supports flexible replacement and expansion of modules; the detachable cascade structure allows the number of nodes to be dynamically increased or decreased according to actual needs, further improving the adaptability of the system; the anti-interference design (such as shielded twisted pair cables, differential input and output modules, etc.) ensures the integrity of audio signals during long-distance transmission and enhances stability in complex industrial environments; the dual-mode operation mechanism (self-test mode detects valid nodes, polling mode time-sharing collection) realizes reliable management of the entire process from node status verification to signal acquisition, further improving monitoring efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] Figure 1 It is a schematic diagram of the existing technical solution;

[0040] Figure 2 Basic concept diagram developed for the design of this invention;

[0041] Figure 3 This is a schematic diagram of the hardware connection of the present invention;

[0042] Figure 4 This is a diagram of the edge processing module structure of the present invention;

[0043] Figure 5 This is a structural diagram of the strobe acquisition module of the present invention;

[0044] Figure 6 This is an example diagram of data transmission according to the present invention;

[0045] Figure 7 This is the overall system structure diagram of the present invention;

[0046] Figure 8 This is a diagram of the acquisition subsystem of the present invention;

[0047] Figure 9 This is a flow chart of the path self-check mode of the present invention;

[0048] Figure 10 This is a flow chart of the polling acquisition mode of the present invention;

[0049] Figure 11 This is a schematic diagram of the cascade structure of the present invention;

[0050] Figure 12 This is a circuit diagram of the cascade structure of the present invention;

[0051] Figure 13 This is a circuit diagram of the cascade acquisition module of the present invention;

[0052] Figure 14 is a schematic diagram of a microphone preamplifier circuit of the present invention;

[0053] Figure 15 This is a schematic diagram of the long-distance multi-stage cascade circuit of the present invention. DETAILED DESCRIPTION

[0054] In order to make the features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description:

[0055] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art to which this application belongs.

[0056] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0057] In view of the problems of difficult wiring and equipment redundancy in current multi-point sound collection and recognition systems, the present invention provides an audio collection system based on a serial polling bus, which is called a "bus-addressed four-wire cascaded long-distance microphone selection collection system." This collection system adopts a serial bus topology rather than a tree-type parallel connection, which makes it easier to install, wire, debug, and maintain in engineering applications. The basic concept of its design and development is as follows: Figure 2 shown.

[0058] Feasibility Analysis of a Serial Acquisition Structure: Assume that a belt idler malfunctions during the operation of a long-distance belt conveyor system. A serial acquisition system is now used to collect the audio signals generated when the malfunction occurs. Considering that in long-distance belt conveyor systems, abnormal audio signals from the belt idler will persist for a certain period of time after the malfunction occurs, the monitoring and identification task places lower real-time requirements on the acquisition system. Abnormal signals can be monitored using a timed polling method on a serial bus. Furthermore, the acoustic signals from the belt idler and other belt-related signals are periodic, with short signal cycles, resulting in a small amount of collected data and a short single acquisition time. During the bus polling process, single-point acquisition does not take up excessive time, thus ensuring efficient system operation.

[0059] To this end, the basic design provided in the embodiments of this invention consists of two main components: a gated acquisition module and an edge processing module. The gated acquisition module consists of pure hardware circuitry without any software, while the edge processing module serves as the system's control host, driving the gated acquisition module. The following describes the process: The edge processing module first sends an operating signal to the gated acquisition module. Upon receiving the signal, the gated acquisition module's hardware circuitry immediately executes the corresponding action.

[0060] Hardware connection diagram as follows Figure 3 As shown, the bus consists of four lines, including two lines for power supply, one line for sending control and acquisition signals, and one line for receiving electrical analog signals of sound.

[0061] The main functions of each part are described as follows:

[0062] 1. The edge processing module is a processing module that connects the back-end server and the front-end selection acquisition module. It is mainly responsible for controlling the acquisition module to poll and collect the audio signal of the belt transmission system or to collect the self-test audio signal of the acquisition module, and transmits the collected signal to the back-end server through the network protocol after processing. Figure 4 shown.

[0063] 2. The strobe acquisition module is composed of pure hardware circuits, such as Figure 5 As shown, it is responsible for receiving and responding to control signals from the edge processing module in real time. It consists of a four-wire cascade and is connected to the edge processing module, namely:

[0064] (1) Power positive: responsible for the positive power level of the module, providing power signals for chips and other circuits

[0065] (2) Negative power supply: responsible for the negative pole of the module power supply. The negative pole in the designed circuit is grounded and used as the ground wire of the chip and other circuits.

[0066] (3) Control signal line: responsible for transmitting the control signal from the edge processing module, using the unipolar return-to-zero code protocol, sending the control signal codewords in sequence, and the corresponding cascade modules receive them in sequence.

[0067] (4) Audio receiving line: responsible for periodically transmitting the analog audio signals of each microphone cascade node back to the system, and returning the collected sound information according to the changes of the control signal line.

[0068] In the strobe acquisition module, each control circuit and MIC head form an independent minimum receiving unit module. These unit modules are serially cascaded to form a complete strobe acquisition module. Each unit module is detachable, allowing the number of receiving units in the strobe acquisition module to be flexibly adjusted to meet different application requirements.

[0069] The components of the unit module are described as follows:

[0070] (1) U1 uses the SM16703P return-to-zero code transmission chip. The distance between the two chips can be up to 30m, which meets the wiring requirements of monitoring long-distance belt conveyor systems. The RGB three pins of U1 can receive communication codes and send different currents. The current can be converted into different voltages through voltage conversion. The current of U1's R pin changes to a voltage through a resistor or optocoupler to control the analog switch U2. Data transmission example is as follows Figure 6 As shown: DIN input data format: Trst + 24-bit grayscale data of the first chip + 24-bit grayscale data of the second chip + ... + 24-bit grayscale data of the Nth chip.

[0071] (2) U2 analog switch selects a three-way electronic analog switch.

[0072] (3) The relay can be equipped with a chip with audio green wave shaping capability, or a single operational amplifier, so that the module can adapt to long-distance audio signal transmission.

[0073] (4) MIC can be active or passive. Passive MIC requires an additional MIC driving circuit.

[0074] The total system constructed based on the above modules consists of a remote server, an edge cabinet, n edge processing modules, and n cascade acquisition modules. Each detection path is composed of an edge processing module and n cascade acquisition modules, such as Figure 7 shown.

[0075] Its core part is the acquisition subsystem consisting of one edge processing module and n cascade acquisition modules, such as Figure 8 shown.

[0076] The main design points include: (1) Cascading is a physical step-by-step gating, rather than a digital communication method that relies on MCU digital coding quantization:

[0077] The smallest controllable acquisition unit of the edge processing module in this embodiment is composed of three chips, such as Figure 5 U1-U3 are shown in the dashed box. The smallest acquisition unit does not include a computing unit like an MCU. This control unit can be cascaded one by one. Using a single-wire return-to-zero (RRZ) data protocol, control data is transmitted to each module via RRZ codes. The output pins of the RRZ code chip control analog switches to select different paths. Therefore, in the designed control acquisition scenario, a theoretically unlimited number of connections are possible.

[0078] (2) The shaping and filtering of the analog signal of this embodiment is transmitted step by step without handshake and conversion into a specific coded digital signal:

[0079] The control data is transmitted through the return-to-zero code transmission chip, which will latch the control signal of the output switch step by step according to the return-to-zero (RESET) signal. Figure 6 As shown in the figure, the processing module sends a 24 * n bits control signal. The cascaded return-to-zero code transmission chips follow the output in descending order. When the zero-level signal is received, the status of each chip is latched and output. Therefore, by sending the 24 bits of control data in sequence, that is, sending the high-address bits first and the low-address bits last, the chip with the corresponding address bit can be confirmed to have received and latched the corresponding control signal when the zero-level signal is received.

[0080] Satisfy the signal transmission of the edge processing module to each control unit.

[0081] Therefore, there is no need for handshaking between the various acquisition strobes. The edge processing module only needs to perform certain encoding and sending, and the audio and electrical signals can be returned through the transmission chip to control the analog switch.

[0082] Since the transmission and response between acquisition modules is pure digital circuit signal transmission, the response is fast, no setting and programming is required, and the reliability is good.

[0083] (3) No need to program specific nodes or physically set phase addresses, they can be changed at will:

[0084] Because the control method uses return-to-zero code, control signals are transmitted step by step. Therefore, once a module is connected to the system, its address is encoded one by one. The closer the access point is to the edge processing module, the lower the acquisition module address. The first acquisition module address is 0, and each module address increases by 1. This address code does not need to be stored. During system startup, the self-test mode detects available modules and determines the actual number of connected modules.

[0085] (4) The stages are connected in series, which is suitable for long-distance linear series connection:

[0086] The modules are designed to be connected in series one by one. Since the number of connections is unlimited, flexible wiring over long distances is convenient. This embodiment incorporates a mid-level shaping chip within the module unit to follow and amplify the signal, ensuring reliable transmission and return.

[0087] (5) The acquisition system only needs one AD to realize the time-sharing sound acquisition of all the pickups of the linear long-distance line:

[0088] In the above logic, since time-sharing acquisition is used, only the AD converter and MCU need to be configured in the edge module, saving equipment costs. Time-sharing acquisition is performed by the edge processing module, which controls the analog switches of chip U1 output one by one according to the return-to-zero code method, releasing the audio signal of the corresponding node for return.

[0089] The collection system designed in this embodiment has two operating modes: path self-check mode and polling collection mode:

[0090] (1) Path self-test mode: During self-test, the specified module U1_R is 0, U1_G is 1 to select the self-test path, and the unspecified module U1_R is 1, U1_G is 0, and U1_B is the corresponding self-test voltage. Figure 4 The transmission rules compile N* 24-bit code-length round-robin control information and send it to the acquisition module one by one. The acquisition module generates a specific self-test voltage signal based on this and directly returns it to the AD sampling and sound recognition system of the main control system.

[0091] More specifically, the control flow is as follows:

[0092] ① The edge processing module generates N * 24-bit round-robin control information, called a control token. Initially, N is set to 10. As the number of monitored signals increases, the processing module sends control signals one by one using a return-to-zero code. The format of the 24-bit self-test control code for the selected module is ([00000000][11111111][00000000 / 11111111]), while the format of the 24-bit self-test control code for the unselected module is ([11111111][00000000][00000000]).

[0093] ② The acquisition module node receives the token selection signal, latches it, and transmits it to the output. In self-test mode, the U1_R and U1_G pins of the selection module output a binary-coded 01 to the U2 analog switch, thereby selecting the module's self-test path. The U1_B output alternates between high and low levels, generating a test audio signal or a specific DC signal. For the remaining modules, U1_R is high, and U1_G and U1_B are low.

[0094] ③ The switch switches the channel according to the status of the RGB control line, connects the acquisition line to the generated self-test audio signal or specific DC signal, and returns it to the AD sampling and sound recognition system of the main control system through relay amplification, thus cyclically self-testing.

[0095] The pseudo code is as follows:

[0096] N = 10

[0097] checkedN = 0

[0098] Start:

[0099] i = checkedN

[0100] for i in N:

[0101] sendOnePointCheck(i) #Send the self-check control code of the specified address bit

[0102] if(checkPointEnable()):

[0103] CheckedN++

[0104] else:

[0105] return CheckedN

[0106] if(CheckedN>N)

[0107] goto Start

[0108] Process such as Figure 9 shown.

[0109] (2) Polling acquisition mode: When the acquisition is working, the designated modules U1_R and U1_G are 1, that is, the MIC path is selected. If the module is not designated, U1_R is 1 and U1_G is 0. Figure 6 The transmission rules compile N * 24-bit code length round-robin control information and send it to the acquisition module one by one. The acquisition module controls the analog switch to select the MIC one by one according to the status of U1_R, collects the signal accordingly, and directly returns it to the AD sampling and sound recognition system of the main control system.

[0110] More specifically, the control flow is as follows:

[0111] ① The edge processing module generates a round-robin control token with a length of N * 24 bits, where N is the number of valid paths obtained during self-test mode. The processing module sends control signals using a return-to-zero code. In round-robin acquisition mode, the 24-bit acquisition control code format for the selected module is ([11111111][11111111][00000000]), and the 24-bit acquisition control code format for the unselected module is ([11111111][00000000][00000000]).

[0112] ② The acquisition module node receives the token strobe signal, latches it, and transmits it to the output. In acquisition mode, the strobe module's U1_R and U1_G pins output a binary-coded 11 to the U2 analog switch, thereby enabling the module's third analog switch path, the audio acquisition path, and switching the receiving route to the pickup. For the remaining modules, U1_R is high, and U1_G and U1_B are low.

[0113] ③ The acquisition module collects the sound and electrical signals generated by the microphone, and returns them to the AD sampling and sound recognition system of the main control system through relay amplification, thus cyclically collecting.

[0114] The pseudo code is as follows:

[0115] N = checkPointsNum()

[0116] for i in N:

[0117] sendOnePointSample(i) #Send the acquisition control code of the specified address bit

[0118] saveOnePointToCache()

[0119] processCacheVoice()

[0120] Flowchart as Figure 10 shown.

[0121] The outstanding features and advantages of the above design of this embodiment include:

[0122] 1. The MIC pickup heads are connected in series. The number of pickup heads can be arbitrarily specified according to actual needs, and the spacing between pickup heads can also be flexibly configured. In addition, the installation location of the pickup points can be flexibly arranged according to the application scenario, facilitating installation and wiring operations, and improving the applicability and convenience of the system.

[0123] 2. According to the working mode of this system, in the application scenario within a range of 200 meters, regardless of the number of MIC acquisition heads, the edge device only needs to be equipped with one analog-to-digital converter (AD), one voice recognition system and one four-core serial bus. This design greatly reduces the system equipment cost, reduces system redundancy, improves operational reliability, and reduces maintenance costs. Figure 11 、 Figure 12 shown.

[0124] 3. After being installed in the monitoring environment, this acquisition system can communicate with the back-end processing server to realize the collection, processing and transmission of audio information of the working status of the long-distance belt conveyor system.

[0125] 4. This system can collect and analyze on-site audio information. By identifying and judging the characteristics of sound signals, it can provide real-time alerts to on-site personnel about the operating status of long-distance belt conveyor systems. At the same time, the system can accurately locate and report potential problem points and related information, providing timely and accurate basis for equipment maintenance and management.

[0126] Finally, this embodiment is Figure 5 A preferred implementation scheme of the circuit implementation details of the key cascade acquisition module shown is further demonstrated and introduced:

[0127] In this cascade acquisition module with three chips as the core, U1-SM16703P is a return-to-zero code chip that transmits control signals, controls the switching circuit to switch paths, and outputs a self-test signal through pin U1_B; U2 is an analog switch for three-path switching; and U3 is a follower amplifier.

[0128] The circuit principle is as follows: Figure 13 As shown:

[0129] Upper access terminal: power supply 24V, power ground GNDI, cascade analog signal output AOUT, return-to-zero signal input DIN;

[0130] Lower input terminal: power supply 24VO, power ground GNDO, cascade analog signal input AIN, return-to-zero code signal output DOUT;

[0131] Chip selection:

[0132] U1-SM16703 is a return-to-zero LED control chip. Through return-to-zero single-line communication, it can simultaneously control the current of U1's OUTR, OUTG, OUTB, and convert it into voltage control through R2, R3, and R4.

[0133] The voltages of the OUTR and OUTG signals serve as the channel select signal for analog switch U2. OUT_B serves as the path self-test voltage signal. By setting different voltages, the conduction voltage drop across the entire cascade path can be measured, thereby identifying any connection faults. The return-to-zero signal is connected via DIN and transmitted to the next-level module via U1's DOUT port.

[0134] The U2-TS5A3359DCUR is a bidirectional single-channel single-pole three-throw analog switch with low on-resistance characteristics. The channel selection is controlled by the input second-line pin.

[0135] The U3-OPA2335AID is a dual-channel operational amplifier chip with low noise, low input bias current, and high precision. It is used to follow the audio signal in the amplification cascade chain to ensure the integrity of the output signal.

[0136] Power supply

[0137] The 24V power supply is connected to the next level power supply 24VO through a 50V / 1A self-recovery fuse to ensure that the next level power supply is automatically disconnected in the event of a short circuit or overload fault. The 24V is converted to 5V by the switching power supply to power the module.

[0138] The principle of microphone preamplifier circuit is as follows Figure 14 As shown:

[0139] U4 is a dual-channel single-power supply rail-to-rail operational amplifier OPA2335AID.

[0140] C5 filters the acoustic signal, attenuating signals above 20 kHz. MIC_IN can be connected to an electret microphone or an active microphone. R16 serves as the bias resistor for the electret microphone. If an active microphone is connected, R16 pull-up bias is not required and can be connected directly to C5.

[0141] U4B is an emitter follower, and its positive terminal is connected to 2.5V by two resistors as the power midpoint of the U4A amplifier.

[0142] U4A and its surrounding power supply form a proportional amplifier. R11 and R12 create a DC voltage bias of 1.25V. R13 and R14 also create a DC voltage bias of 1.25V. R19 is a negative feedback resistor. Its AC amplification factor is (R19 + R13 / / R14) / (R13 / / R14) = (R19 + 5000) / 5000. Adjust R19 to keep the maximum output signal amplitude below 1.2V.

[0143] Circuit simulation experiment

[0144] Long distance multi-stage cascade:

[0145] like Figure 15 As shown, by cascading multiple modules, long-distance signal transmission is tested, and variable resistors are set between cascades to test signal attenuation. The test steps are as follows:

[0146] 1. Set the MIC part of the rightmost cascade module to input a sine wave signal with an amplitude of 20mV and a frequency of 5kHz.

[0147] 2. Set up an oscilloscope on the AOUT output of the leftmost cascade module;

[0148] 3. The last module is connected to the MIC signal through the simulated return-to-zero code cascade control;

[0149] 4. The remaining modules are controlled to be in signal transmission mode through simulated return-to-zero code cascade;

[0150] 5. Adjust the variable resistance test signal attenuation between cascades;

[0151] 6. Observe the collected audio signal in the oscilloscope on the far left.

[0152] Since a relay follower amplifier module is provided in the cascade module and the analog switch in the module is a low on-resistance switch, the integrity of the signal can be maintained during the inter-stage transmission, and the signal amplitude of the first-stage output can be maintained.

[0153] Signal-to-noise ratio under multi-node cascade:

[0154] The system maintains a certain signal-to-noise ratio through the following strategies:

[0155] 1. The output amplitude of the microphone preamplifier circuit is adjusted to about 1V so that the interference noise amplitude is smaller than the output signal amplitude.

[0156] 2. During the transmission process, since the signal path only passes through the emitter follower of the op amp and the analog switch, there is no other noise source. At the same time, the emitter follower has sufficient load capacity, which effectively improves the signal-to-noise ratio.

[0157] 3. Shielded wires are used during the transmission process to shield external coupled voltage interference.

[0158] 4. Depending on the specific application scenario, differential input and output modules can be connected to AOUT and AIN to further improve the signal-to-noise ratio.

[0159] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0160] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

[0161] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of bus-addressed four-wire cascaded long-distance microphone selection acquisition systems based on the inspiration of the present invention. All equivalent changes and modifications made within the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A bus-addressable four-wire cascaded long-distance microphone gating acquisition system, characterized in that: include: An edge processing module, configured to generate and send a return-to-zero code control signal including a self-test mode code or a polling mode code; Several strobe acquisition modules are serially cascaded via a four-wire bus, wherein the four-wire bus includes a positive power line, a negative power line, a control line, and an audio line; Each of the strobe acquisition modules is composed of a pure hardware circuit without a computing unit, and the pure hardware circuit includes: A return-to-zero code chip is used to receive the return-to-zero code control signal and transmit it step by step to the next-level strobe acquisition module, and output the control signal to the analog switch; An analog switch array, used for switching paths according to the control signal of the return-to-zero code chip, and selecting a microphone or a self-test signal; Relay amplifier chip, used to follow and amplify audio signals to compensate for long-distance transmission attenuation; The edge processing module is configured with only one analog-to-digital converter, and realizes time-sharing acquisition of audio signals of all cascaded acquisition modules by time-sharing gating the analog switch; The edge processing module supports two operating modes: Self-test mode: dynamically detect the number of valid strobe acquisition modules by sending self-test mode code; Polling mode, sending a polling mode code according to the number of valid selected acquisition modules, and selecting the microphone node by node to collect audio signals; Among them, the self-test mode takes precedence over the polling mode.

2. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The address of the strobe acquisition module is automatically determined by the access sequence. The address of the first strobe acquisition module accessed is 0, and the addresses of the subsequent strobe acquisition modules accessed are incremented in sequence. The address information is dynamically detected and acquired through the self-test mode.

3. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The code length of the return-to-zero code control signal is 24 bits, where: The self-test mode code includes a first group of control bits, a second group of reserved bits, and a switchable third group of self-test signal bits for selecting the module to generate a self-test signal; the self-test signal bits are alternating level bits used to generate a test audio signal; The polling mode code includes a first group of reserved bits, a second group of control bits for switching the strobe module to the microphone acquisition path, and a third group of reserved bits.

4. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The relay amplifier chip is a low-noise operational amplifier used to compensate for signal attenuation during long-distance transmission, so that the audio signal amplitude loss is controllable when the cascade transmission distance is not less than 200 meters.

5. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The strobe acquisition module also includes a microphone preamplifier circuit composed of an operational amplifier, a resistor voltage divider network and a negative feedback resistor. The output audio signal amplitude is lower than 1.2V by adjusting the negative feedback resistor.

6. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: Each cascade module of the power positive line is independently provided with a self-recovery fuse, which is used to automatically disconnect the lower power supply when a short circuit or overload occurs in the cascade module.

7. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The audio line adopts a shielded twisted pair, and the cascade interface is configured with a common-mode filter capacitor, or connected to a differential input and output module to suppress external coupling voltage interference.

8. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 1, characterized in that: The strobe acquisition module adopts a detachable cascade structure and supports dynamic increase or decrease in the number of modules.

9. The bus-addressable four-wire cascaded long-distance microphone gating acquisition system according to claim 5, characterized in that: The output amplitude of the preamplifier circuit is adjusted to 1V, so that the noise amplitude is relatively reduced.

Images