Single-channel mode I2S interface MEMS microphone single-differential bus transmission method

Abstract

The application belongs to the technical field of I2S interface MEMS microphone voice sampling data transmission, and particularly relates to a single-channel mode digital MEMS microphone I2S interface and single-differential bus interface conversion transmission method. When a MEMS microphone protocol interface module is in a slave state, a configuration instruction issued by a remote device is received, and the configuration instruction contains a configuration frame synchronization code and MEMS microphone configuration information. After the frame synchronization code is correctly identified and the configuration instruction is received, the protocol module is switched from a receiving state to a sending state, audio data is sampled according to the configuration instruction content, the sampled data is encapsulated according to a serial communication data format, and then the data is transmitted in real time to the remote device through a single-differential serial bus. The idle timing of the I2S protocol is used to receive an initialization instruction, the utilization rate of signal resources is improved, the number of IO interfaces is reduced by using single-line differential serial bus transmission, and electromagnetic interference of the MEMS microphone I2S bus in the transmission process is avoided.

Description

A Single-Channel Mode I2S Interface MEMS Microphone Single Differential Bus Transmission Method Technical Field

[0001] This invention belongs to the field of microphone signal transmission technology, specifically relating to a single-channel mode I2S interface MEMS microphone single differential bus transmission method. Background Technology

[0002] The I2S (Inter-IC Sound) bus is a bus standard developed by Philips for audio data transmission between digital audio devices. This bus is used for data transmission between audio devices and is widely used in various multimedia systems. The I2S bus has three data signal lines: serial clock (SCK), serial data (SD), and word select (WS). The serial clock corresponds to each bit of digital audio data, and SCK has one pulse. The SCK clock frequency is 2 × sample bits × sampling frequency. SD represents the audio data in two's complement binary, and the most significant bit is always transmitted first.

[0003] Field Selection Signal Line WS: Typically used for left and right channel data switching control. When WS is low, the I2S signal line interface latches the output data on the rising edge of the SCK clock; when WS is high, the I2S signal line interface is high impedance.

[0004] The I2S bus interface is based on a three-wire serial data bus interface with a master / slave structure. The master device provides the clock and can initiate read or write operations to slave devices. When multiple slave devices exist on the bus, to initiate a transmission, the master device pulls the slave device select line WS low and then initiates data transmission or reception via the CLK and DATA lines respectively. Each slave device requires a separate slave select signal, resulting in a total of N+2 signals, where N is the number of slave devices on the bus. Having multiple slave devices on the bus inevitably leads to excessive signal line resources. Furthermore, because the I2S bus uses single-ended signals for data transmission, it is susceptible to noise interference, making it unsuitable for applications such as large microphone arrays or long cross-board connections. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a single-channel mode I2S interface MEMS microphone single differential bus transmission method, the specific technical solution of which is as follows:

[0006] A single-channel mode I2S interface MEMS microphone single differential bus transmission method includes:

[0007] The remote device is connected to the single-bus differential interface of the protocol interface module via a single differential serial bus, and the MEMS microphone is connected to the I2S bus interface of the protocol interface module via an I2S protocol signal line.

[0008] In single-channel mode, the protocol interface module adheres to the following communication protocol, converting the I2S protocol signal line transmission of the MEMS microphone into single differential serial bus transmission, thereby realizing information interaction and data transmission between the MEMS microphone I2S interface and remote devices; the communication protocol specifically includes:

[0009] In step S1, the protocol interface module is in slave mode. At this time, the single differential serial bus is kept at a high level through external hardware circuitry, and the single bus differential interface of the protocol interface module is in high-impedance receiving mode. The protocol interface module, as the receiver, waits to receive the activation configuration command sent by the remote device to initialize and configure the MEMS microphone. The activation configuration command is sent periodically. The activation protocol interface module reads the audio data of the MEMS microphone through the I2S protocol signal line. The frequency of sending the activation configuration command is the sampling frequency of the MEMS microphone signal.

[0010] Step S2: After correctly identifying the frame synchronization code and receive activation configuration command sent by the remote device, the protocol interface module completes the switch from receiving state to sending state. At this time, the protocol interface module acts as the sender. The protocol interface module encapsulates the audio signal of the MEMS microphone sampled through the I2S protocol signal line according to the data frame format of serial communication, and then transmits it to the remote device in real time through the single differential serial bus.

[0011] Step S3: After the audio data transmission is completed, the single-bus differential interface of the protocol interface module releases the bus and waits for the activation configuration command sent by the remote device in the next cycle. That is, the single-bus differential interface of the protocol interface module is in a high-impedance receiving state and remains idle for two BCLK cycles before the next data transmission begins. During the idle period, the single-wire differential serial signal line is kept at a high level through external hardware circuitry.

[0012] Furthermore, the activation configuration instruction includes address configuration information and read / write configuration information, as well as configuration of the MEMS microphone's clock SCK, sampling bit depth, and data transmission rate.

[0013] Furthermore, the data transmission rate = 32 × 2 × sampling frequency.

[0014] Furthermore, the frame format of the activation configuration instruction includes a start bit, a Barker code synchronization bit, a read / write bit, an address bit, a write configuration bit, and a read / write switching protection bit;

[0015] The start bit is a marker for the start of data, starting from 0, i.e., low level. When the protocol interface module is in the receiving state, it detects that the single-bus differential interface is low level and then starts receiving the activation configuration instruction data sent by the remote device.

[0016] The Barker code synchronization bit is used to achieve frame synchronization, and the code type is a seven-bit Barker code.

[0017] The read / write bit is a flag bit for read / write commands. When the read / write bit is 1, it is a read command, indicating that this command frame is a start data transmission command, used to transmit audio data start command of MEMS microphone; when the read / write bit is 0, it is a write command, indicating that this command frame is a configuration frame.

[0018] The address bits are used to configure the device address of the MEMS microphone;

[0019] The write configuration bit contains the MEMS microphone's clock SCK, sampling bit depth, and data transmission rate configuration information. The read / write configuration information is only valid when the read / write bit is 0.

[0020] The read / write switching protection bit is the time interval for the port to release the bus after the read / write configuration is completed. It is used to provide a buffer time for the transmit / receive switching of the single-bus differential interface of the protocol interface module. At this time, the single-bus differential interface of the protocol interface module is in a high-impedance state.

[0021] Furthermore, the audio data frame format includes a start bit, data bits, and an end bit;

[0022] The start bit is a marker indicating the start of data frame transmission, starting with 0, i.e., low level.

[0023] The data bits are digitized audio signal data from a MEMS microphone sampled via the I2S protocol signal line.

[0024] The end bit is a marker indicating the end of a data frame.

[0025] Furthermore, after the protocol interface module completes the switch from the receive state to the transmit state, and before the audio data is transmitted, it is idle for two BCLK cycles. During the idle period, the single differential serial bus is kept at a high level by external hardware circuitry.

[0026] The BCLK period mentioned above is the clock SCK of the MEMS microphone.

[0027] The beneficial effects of this invention are as follows: This invention provides a single-channel mode I2S interface MEMS microphone single differential bus transmission method. Based on the characteristics of the I2S protocol, the single-bus differential interface of the protocol interface module receives the activation configuration command sent by the remote device. The command includes address configuration and read / write configuration information, configuring the MEMS microphone's clock (SCK), sampling bit depth, and data transmission rate. After correctly identifying the frame synchronization code and completing the configuration command reception, the protocol interface module switches from the receiving state to the transmitting state. The MEMS microphone samples audio data according to the sampling rate of the activation configuration command. The sampled audio data is encapsulated according to the serial communication data format and then transmitted to the remote device in real time via the single differential serial bus. This invention utilizes the idle timing of the I2S protocol to receive the initialization activation configuration command, improving the utilization rate of signal resources. Simultaneously, the use of single differential serial bus transmission reduces the number of I / O interfaces and lowers electromagnetic interference on the I2S single-ended signal line during transmission. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0029] Figure 1 is a schematic diagram of the system structure of the single-channel mode MEMS microphone single differential bus transmission method of the present invention;

[0030] Figure 2 shows the timing diagram of the SEL pin of the I2S protocol MEMS microphone device when it is low.

[0031] Figure 3 shows the timing diagram of the SEL pin of the I2S protocol MEMS microphone device when it is high.

[0032] Figure 4 is a timing diagram of the instruction frame and data frame of the present invention;

[0033] Figure 5 is a flowchart of the single-channel mode MEMS microphone single differential bus transmission method of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0036] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0037] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0038] The I2S protocol is a three-wire serial data bus interface protocol. During long-distance transmission or transmission between multiple MEMS microphone devices, signal interference between signal lines may occur, consuming excessive signal resources. To address this issue, this invention provides a single-channel mode I2S interface MEMS microphone single differential bus transmission method, as shown in Figure 1, including:

[0039] The remote device is connected to the single-bus differential interface of the protocol interface module via a single differential serial bus, and the MEMS microphone is connected to the I2S bus interface of the protocol interface module via an I2S protocol signal line.

[0040] In single-channel mode, the protocol interface module adheres to the following communication protocol, converting the I2S protocol signal line transmission of the MEMS microphone into single differential serial bus transmission, enabling information exchange and data transmission between the MEMS microphone's I2S interface and remote devices. The single differential serial bus uses differential signal transmission; there are no reference level lines in the differential signal transmission lines—all are signal lines. The voltage difference between signal lines represents symbols 0 and 1. Compared to level signals, differential signals are less susceptible to interference, resulting in more stable signal quality.

[0041] The I2S timing diagrams for single-channel mode are shown in Figures 2 and 3. Specifically, as shown in Figure 2, the SEL pin of the MEMS microphone device is at a low level. When WS is low, the I2S signal line interface latches the output data on the rising edge of the SCK clock; when WS is high, the I2S signal line interface is at high impedance. As shown in Figure 3, the SEL pin of the MEMS microphone device is at a high level. When WS is high, the I2S signal line interface latches the output data on the rising edge of the SCK clock; when WS is low, the I2S signal line interface is at high impedance. According to the I2S timing diagrams, regardless of the level of the SEL pin of the MEMS microphone device, the I2S signal line interface is in a high-impedance state during half a cycle of WS, and the SCK clock line still provides a 32-cycle clock signal. Based on the characteristics of the I2S protocol timing diagrams, this invention specifically adopts the following communication protocol:

[0042] In step S1, the MEMS microphone protocol interface module is in slave mode. At this time, the single differential serial bus is kept at a high level through external hardware circuitry, and the single bus differential interface of the protocol interface module is in a high-impedance receiving state. The protocol interface module, as the receiver, waits to receive the activation configuration command sent by the remote device to initialize and configure the MEMS microphone. The activation configuration command is sent periodically. The activation protocol interface module reads the audio data of the MEMS microphone through the I2S protocol signal line. The frequency of sending the activation configuration command is the sampling frequency of the MEMS microphone signal.

[0043] The activation configuration command includes address configuration information and read / write configuration information, as well as configuring the MEMS microphone's clock (SCK), sampling bit depth, and data transmission rate. The data transmission rate is calculated as 32 × 2 × sampling frequency.

[0044] The frame format of the activation configuration instruction is shown in Figure (4). The frame length of the instruction is 32 bits, consisting of a 1-bit start bit, a 7-bit Barker code synchronization bit, a 1-bit read / write bit, an 11-bit address bit, a 10-bit write configuration bit, and a 2-bit read / write switching protection bit. The start bit is the marker for the start of data, starting from 0, i.e., low level. When in the receiving state, a low level is detected to start receiving instruction data. The Barker code synchronization bit realizes frame synchronization. In digital communication systems, synchronization is a very important issue. In order for the received symbols to be understood, it is necessary to know how they are grouped. The receiving end needs to perform frame synchronization on the data. Barker code is a non-periodic binary sequence with special rules. Its local autocorrelation function has a sharp single-peak characteristic, which meets the main requirements of continuous insertion frame synchronization code. The Barker code type used in this invention is a seven-bit Barker code. The read / write bit is a flag for read / write commands. When the read / write bit is 1, it's a read command, indicating that this command frame is for initiating data transmission, used to transmit audio data from the MEMS microphone. When the read / write bit is 0, it's a write command, indicating that this command frame is a configuration frame. The address bit is used to configure the device address of the MEMS microphone; there are 2 address bits. 11 The address space is followed by a write configuration bit and a read / write switch protection bit. The write configuration bit contains configuration information for the MEMS microphone's clock (SCK), sampling bit depth, and data transmission rate. This configuration information is only valid when the read / write bit is 0. The read / write switch protection bit is the time interval for the port to release the bus after the read / write configuration is complete. It provides a buffer time for the transmit / receive switching of the differential interface of the protocol interface module. During this time, the single-bus differential interface of the protocol interface module is in a high-impedance state, and the single differential serial bus is kept high through external hardware circuitry.

[0045] In step S2, after correctly identifying the frame synchronization code and receive activation configuration command sent by the remote device, the protocol interface module switches from the receive state to the transmit state. It idles for two BCLK cycles before audio data transmission, during which the single differential serial bus is kept high by external hardware circuitry. The BCLK cycle is the clock SCK of the MEMS microphone; the two idle BCLK cycles provide a buffer time for the MEMS microphone to start audio data sampling. At this point, the protocol interface module acts as the sender, encapsulating the audio signal sampled by the MEMS microphone according to the serial communication data frame format, and then transmitting it to the remote device in real time via the single differential serial bus.

[0046] The audio data frame format is shown in Figure 4. The frame length is 26 bits, consisting of a 1-bit start bit, 24-bit data bits, and a 1-bit end bit. The start bit marks the beginning of the data frame and starts at a low level, similar to the command frame. The data bits are the digitized audio signal data sampled by the MEMS microphone. The end bit marks the end of the data frame.

[0047] Step S3: Once the remote device successfully receives and identifies the end bit of the data frame, it completes one cycle of transmit / receive operation. This also means that the single-bus differential interface of the protocol interface module has successfully transmitted the audio data. After completing the audio data transmission, the single-bus differential interface of the protocol interface module releases the bus and waits for the activation configuration command sent by the remote device in the next cycle. That is, the single-bus differential interface of the protocol interface module is in a high-impedance reception state and remains idle for two BCLK cycles before the next data transmission begins. During the idle period, the single-wire differential serial signal line is kept high through external hardware circuitry.

[0048] The specific process of this invention is shown in Figure (5). The protocol interface module is in slave mode. At this time, the single-bus differential interface of the protocol interface module is in a high-impedance receiving state, waiting for the activation configuration command from the remote device. The activation configuration command is sent periodically to activate the protocol interface module as a slave to read the audio data of the MEMS microphone through the I2S protocol signal line. After frame synchronization, read / write configuration and address configuration operations are performed according to the relevant information of the activation configuration command. This operation lasts for 32 SCK cycles. After correctly identifying the frame synchronization code and receiving the activation configuration command, the protocol interface module completes the switch from receiving state to sending state. The MEMS microphone samples the audio data according to the set parameters, encapsulates the data frame structure, and transmits it to the remote device through the single differential serial bus. According to the timing characteristics of I2S, the protocol interface module receives the activation configuration command and transmits audio data periodically. This is equivalent to the protocol interface module waiting for the remote device to periodically receive the activation configuration command to wake it up and periodically transmit data. The wake-up period or the data transmission period is the sampling rate of the MEMS microphone.

[0049] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0050] In the embodiments provided in this application, it should be understood that the division of units is only a logical functional division. In actual implementation, there may be other division methods, such as multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A single-channel mode I2S interface MEMS microphone single differential bus transmission method, characterized in that, include: The remote device is connected to the single-bus differential interface of the protocol interface module via a single differential serial bus, and the MEMS microphone is connected to the I2S bus interface of the protocol interface module via an I2S protocol signal line. In single-channel mode, the MEMS microphone and the remote device follow the following communication protocol to convert the three-wire serial bus transmission of the MEMS microphone's I2S interface into a single differential serial bus transmission, thereby realizing information interaction and data transmission between the MEMS microphone's I2S interface and the remote device. The communication protocol specifically includes: Step S1, the protocol interface module is in slave mode. At this time, the single differential serial bus is kept at a high level through external hardware circuitry, and the single-bus differential interface of the protocol interface module is in a high-impedance receiving state. The protocol interface module, as the receiver, waits to receive the activation configuration command sent by the remote device to initialize and configure the MEMS microphone. The activation configuration command is sent periodically, and the activation protocol interface module reads the audio data of the MEMS microphone in real time through the I2S protocol signal line. Step S2: After correctly identifying the frame synchronization code and receive activation configuration command sent by the remote device, the protocol interface module switches from the receive state to the send state. At this time, the protocol interface module acts as the sender. The protocol interface module encapsulates the audio signal sampled by the MEMS microphone according to the serial communication data format, and then transmits it to the remote device in real time through a single differential serial bus. Step S3: After the audio data transmission is completed, the single-bus differential interface of the protocol interface module releases the bus and waits for the activation configuration command sent by the remote device in the next cycle. That is, the single-bus differential interface of the protocol interface module is in a high-impedance receive state and remains idle for two BCLK cycles before the next data transmission begins. During the idle period, the single-wire differential serial signal line is kept high through external hardware circuitry. The activation configuration command includes address configuration information and read / write configuration information, as well as configuring the MEMS microphone clock SCK, sampling bit depth, and data transmission rate. The frame format of the activation configuration command includes a start bit, Barker code synchronization bit, read / write bit, address bit, write configuration bit, read... The write switching protection bit; the start bit is a data start flag, starting from 0, i.e., low level. When the protocol interface module is in the receiving state, it detects that the single-bus differential interface is low level and starts receiving the activation configuration command data sent by the remote device; the Barker code synchronization bit is used to realize frame synchronization, and the code type is a seven-bit Barker code; the read / write bit is a flag bit for read / write commands. When the read / write bit is 1, it is a read command, indicating that this command frame is to start data transmission, used to transmit the audio data start command of the MEMS microphone; when the read / write bit is 0, it is a write command, indicating that this command frame is a configuration frame; the address bit is used to configure the device address of the MEMS microphone; the write configuration bit contains the MEMS microphone clock SCK, sampling bit depth, and data transmission rate configuration information. The read / write configuration information is only valid when the read / write bit is 0; the read / write switching protection bit is the time interval for the port to release the bus after the read / write configuration is completed, used to provide a buffer time for the transmit / receive switching of the single-bus differential interface of the protocol interface module. At this time, the single-bus differential interface of the protocol interface module is in a high-impedance state.

2. The single-channel mode I2S interface MEMS microphone single differential bus transmission method according to claim 1, characterized in that, The data transmission rate = 32 × 2 × sampling frequency.

3. The single-channel mode I2S interface MEMS microphone single differential bus transmission method according to claim 1, characterized in that, The audio data frame format includes a start bit, data bits, and an end bit; the start bit is a marker indicating the start of data frame transmission, starting with 0, i.e., low level; the data bits are digitized audio signal data from a MEMS microphone sampled via the I2S protocol signal line; and the end bit is a marker indicating the end of the data frame.

4. The single-channel mode I2S interface MEMS microphone single differential bus transmission method according to claim 3, characterized in that, After the protocol interface module completes the switch from the receive state to the transmit state, and before the audio data is transmitted, it idles for two BCLK cycles. During the idle period, the single differential serial bus is kept at a high level by external hardware circuitry; the BCLK cycle is the clock SCK of the MEMS microphone.

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