A device for realizing long-distance transmission of KVM multi-channel audio

Abstract

The application provides a device for realizing long-distance transmission of KVM multi-channel audio, comprising module A, module B and a controlled host computer, wherein module A comprises an FPGA, an RJ45 interface 1, an RJ45 interface 2 and an RJ45 interface 3, module B comprises an RJ45, an FPGA, an MCU and a USB interface, the controlled host computer is bidirectionally connected with the USB interface of module B, the FPGAs of module A and module B are both used for transmission by using BLVDS interfaces, the transmission medium is a pair of differential lines, half-duplex communication is formed, the communication signal is a BLVDS level signal, the RJ45 of module B is bidirectionally connected with the RJ45 interface 1 of module A, and the FPGA of module A is used for audio decoding output. The application has the beneficial effects that the FPGA chip is used for processing in the host processor, and the BLVDS signal is directly used for data transmission, so that the cost is saved, and a faster transmission rate can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of data transmission, and in particular to a device for realizing long-distance transmission of KVM multi-channel audio. Background Art

[0002] Nowadays, there are many servers in the subway machine room, mainly including servers for communication, integrated monitoring, ticketing system, passenger system, etc. In order to ensure the stable and reliable operation of these servers, and at the same time ensure the safety of equipment and personal safety, the number of relevant personnel entering the machine room for on-site operation should be reduced as much as possible when maintaining and monitoring the servers. In response to this, the KVM system was born. In some application scenarios, not only the video image of the controlled host is needed, but also the audio data of the controlled host needs to be played. Especially when controlling multiple controlled hosts at the same time, multiple channels of audio data will be transmitted at the same time, and as the transmission distance increases, there are shortcomings such as signal attenuation and poor interference resistance. How to process multiple channels of audio data and play them at a farther control host has become a problem that needs to be solved. In order to solve these problems, the present invention uses differential signals to transmit audio data, so that the transmission distance and anti-interference ability of audio data are greatly enhanced, and the transmission line is only an ordinary Category 5e network cable, or even an ordinary twisted pair cable, and multiple channels of audio data can be encoded and played at the same time.

[0003] Existing technologies use an audio / video selector to process multiple audio channels, selecting a specific channel for transmission. This fails to meet the requirements for simultaneous multi-channel audio transmission. For long-distance transmission, traditional RS485 transmission is used, requiring the addition of an additional RS485 transceiver circuit to the FPGA processing chip, increasing design costs. Furthermore, traditional RS485 chips have a limited transmission rate of up to 10 Mbps. Summary of the Invention

[0004] To solve the above problems, the present invention provides a device for realizing long-distance transmission of multi-channel audio of KVM. The device adopts the MCU+FPGA control method, has the transmission function of multi-channel audio, and also realizes the function of simultaneous transmission of multi-channel audio. In addition, for long-distance transmission, there is no need to add an additional 485 chip. The FPGA can not only realize audio processing, but also directly use its own bus-type low voltage differential (BLVDS) for long-distance transmission. In addition, the transmission medium only requires a pair of differential lines, a pair of differential lines in the network cable or a twisted pair, and the speed can reach 20Mbps-50Mbps, which greatly improves the cost and speed. It mainly includes: module A, module B and controlled host. Module A includes FPGA, RJ45 interface 1, RJ45 interface 2 and RJ45 interface 3. Module B includes RJ45, FPGA, MCU and USB interface. The controlled host is bidirectionally connected to the USB interface of module B. The FPGAs of module A and module B both use BLVDS interface for transmission. The transmission medium is a pair of differential lines to form half-duplex communication. The communication signal is a BLVDS level signal. The RJ45 of module B is bidirectionally connected to the RJ45 interface 1 of module A. The FPGA of module A is used for audio decoding output.

[0005] Furthermore, the MCU includes an STM32F103C8T6 chip and its peripheral circuits, a crystal oscillator circuit, a reset circuit and a download circuit.

[0006] Furthermore, the differential lines are connected to the IO ports of the FPGAs of module A and module B. In order to prevent signal interference and mutual interference between two adjacent pairs of differential lines, the P end of the differential line is set to pull up and the N end is set to pull down.

[0007] Furthermore, the MCU of module B allows the controlled host to recognize the USB sound card device, and at the same time uses the SPI high-speed interface to transmit audio data to the FPGA of module B. The FPGA of module B uses the BLVDS interface to send audio data or audio requests to module A through the network cable.

[0008] Furthermore, the data flow of module B is as follows: the FPGA of module B receives the audio request command and sends it to the MCU through the SPI1 host. The MCU uses the USB bus to interact with the controlled host. The controlled host sends the audio data to the MCU. The MCU then sends the data to the FPGA of module B through the SPI2 host. The FPGA of module B uses the BLVDS interface to send the data to module A.

[0009] Furthermore, when simultaneous transmission of multiple audio channels is required, module A can be connected to multiple modules B.

[0010] Furthermore, the FPGA of module A converts the differential signal transmitted from module B into a single-ended signal through the BLVDS interface for processing. After serializing the multiple channels of audio data into one channel of data, the multiplexing of the multiple channels of audio is completed. Then, the multiplexed multiple channels of audio serial data are sent to the audio decoding module for decoding and playback at each aligned clock.

[0011] The technical solution provided by the present invention has the beneficial effect of using an FPGA chip for processing in a main processor and directly using its BLVDS signal for data transmission, thereby saving costs and achieving a faster transmission rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0013] Figure 1 This is a framework diagram of a device for implementing long-distance transmission of KVM multi-channel audio in an embodiment of the present invention.

[0014] Figure 2 This is a signal flow diagram of the FPGA portion in an embodiment of the present invention.

[0015] Figure 3 It is the data flow diagram of module B in the embodiment of the present invention.

[0016] Figure 4 This is a block diagram of multi-channel audio transmission in an embodiment of the present invention.

[0017] Figure 5 This is a flowchart of multi-channel audio processing in an embodiment of the present invention.

[0018] Figure 6 It is a multiplexing timing diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0020] Please refer to Figure 1 , Figure 1This is a schematic diagram of a device for long-distance transmission of multi-channel KVM audio, according to an embodiment of the present invention. The device specifically comprises: module A, module B, and a controlled host. A Category 5e or Category 6 network cable is used as the transmission medium. Essentially, the transmission medium only requires one differential pair within the cable; the remaining differential pairs are used to transmit VGA video signals within the KVM system. Module A includes an FPGA, RJ45 ports 1, 2, and 3. Module B includes an RJ45, FPGA, MCU, and a USB port. The controlled host is bidirectionally connected to the USB port of module B, and the RJ45 port of module B is bidirectionally connected to the RJ45 port 1 of module A. The FPGA of module A is used for audio decoding and output.

[0021] like Figure 2 As shown, the FPGAs in both modules A and B use a BLVDS interface for long-distance transmission. The transmission medium is a pair of differential lines, enabling half-duplex communication, with BLVDS level signals. For transmission distances of 50-100 meters, no additional signal modulation chip is required; the differential lines can be directly connected to the IO ports of the two FPGAs. Crucially, to prevent signal interference and mutual interference between adjacent differential lines, the P-terminal (io_p) of the differential pair is set to pull-up, and the N-terminal (io_n) of the differential pair is set to pull-down. The transmitted data protocol uses a custom protocol.

[0022] BLVDS (Low-Voltage Differential Signaling) is a differential signaling technology that offers low power consumption, low bit error rate, low crosstalk, and low radiation. This transmission technology can reach speeds exceeding 155Mbps. The core of LVDS technology is high-speed differential data transmission using extremely low voltage swings, enabling point-to-point or point-to-multipoint connections. The transmission medium can be copper PCB traces or balanced cables. BLVDS is a new family of bus interface circuits based on LVDS technology, specifically designed for multi-point cable or backplane applications. It features a low-voltage differential signal of approximately 250mV and fast transition times.

[0023] The MCU part of module B can also be said to be a sound card device that collects audio from the controlled server. It contains the STM32F103C8T6 chip and its peripheral circuits, crystal oscillator circuit, reset circuit, download circuit, etc. Its main function is to provide a USB sound card device driver, which allows the controlled host to recognize the USB sound card device. The sound card device connects to the controlled host through the USB port, collects the audio data from the controlled host, and uses the SPI high-speed interface to transmit the audio data to the FPGA of module B. The FPGA of module B uses the BLVDS interface to send the data through the network cable. Its data flow diagram is as follows Figure 3As shown, two pairs of SPI interfaces form true full-duplex communication. When data needs to be sent, it is sent directly through the SPI master. The FPGA in module B receives an audio request command and sends it to the MCU via the SPI1 master. The MCU interacts with the controlled host using the USB bus. The controlled host sends audio data to the MCU, which then sends the data to the FPGA in module B via the SPI2 master. The FPGA in module B then transmits the data using the BLVDS interface. In module B, if only one SPI interface is used for communication, such as the FPGA acting as the SPI master and the MCU as the SPI slave, then when the MCU wants to return data to the FPGA, the FPGA must first send a certain number of bytes of invalid data, significantly increasing the complexity of the communication protocol and making it cumbersome to handle.

[0024] like Figure 4 As shown in the figure, when multiple audio channels need to be transmitted simultaneously, module A can be connected to multiple modules B. After the sound cards of multiple modules B send out the audio data, it is transmitted 50-100 meters via the network cable to reach the BLVDS interface of the FPGA in module A. The FPGA in module A multiplexes the multiple audio signals and then transmits them for decoding and playback.

[0025] The FPGA of module A converts the differential signal transmitted from module B into a single-ended signal through the BLVDS interface for processing, serializes the multi-channel audio data into one channel, and sends it to the upper-layer processing module. The specific processing flow is as follows:

[0026] The FPGA of module A sends an audio function enable command to module B, and numbers the modules B that have audio enabled in turn. At this time, module B receives the audio PCM data from the controlled host through the USB interface and stores it in the buffer. Module A sends a request audio data command at regular intervals. After receiving the request, the corresponding module B returns the data to module A. Figure 5 As shown in the figure, module A opens a receive buffer FIFO for each module B, denoted as R_FIFO, and opens an additional serial FIFO to multiplex multiple audio data. According to the IIS audio format, module A takes out one byte of data from R_FIFO and puts it into the serial FIFO in turn under each corresponding BCLK (bit clock) within an LRC (aligned clock), thus completing the multiplexing of multiple audio channels. The multiplexing timing diagram is shown in the figure. Figure 6 As shown, the multiplexed multi-channel audio serial data is then sent to the audio decoding module for decoding and playback under each LRC.

[0027] In this embodiment, the FPGA used as the main processor in module A and module B can be replaced with other chips with a BLVDS interface;

[0028] The MCU chip in this embodiment can be replaced by a domestic compatible chip, such as HK32, CKS32, GD32, CH32, APM32, or a single-chip microcomputer of the NXP LPC series.

[0029] To address the challenges of long-distance data transmission and data rate limitations, traditional 485 transmission solutions require additional chip control circuits and offer low data rates. This invention directly utilizes an FPGA chip and its BLVDS level signals to connect a pair of differential lines directly to the IO port, and also performs pull-up and pull-down operations on the IO port. This eliminates the need for additional control circuits and chips, and can achieve 20Mbps over a transmission distance of 50-100 meters.

[0030] When the MCU and FPGA exchange data, dual SPI communication is used to solve the problem that during SPI communication, the host must initiate a data request before the slave can return data to the host.

[0031] To solve the problem of simultaneous transmission of multi-channel audio data, a master-slave mode audio data transmission method is adopted. The multi-channel parallel request, parallel reception and serial output method are used to multiplex and output the multi-channel audio data at the same time, and then decode and play them.

[0032] Traditional USB sound cards have a maximum data transmission distance of only 5 meters, making them impractical for long-distance transmission. Furthermore, conventional KVM systems do not support the simultaneous transmission of multiple channels of audio data. Therefore, the present invention converts multi-channel audio data into BLVDS level signals for long-distance transmission, while simultaneously utilizing a receiving device to multiplex the multiple differential data channels into one channel for transmission and playback. This device offers advantages such as simple design, excellent versatility, strong anti-interference capabilities, low cost, and a short development cycle. It is applicable to any multi-channel audio long-distance transmission solution and offers excellent economic benefits.

[0033] The beneficial effects of the present invention are as follows: currently, conventional solutions adopted by products on the market mostly use RS485 transmission for long-distance transmission. A 485 transmitting chip is used next to the main processor to convert single-ended signals into differential signals for transmission. Then, an RS485 receiving chip is used to convert the differential signals into single-ended signals before transmitting them to the main processor for processing. This adds additional circuits and chips, and the transmission rate is limited by the 485 chip, making it impossible to achieve a faster transmission rate. The present invention uses an FPGA chip for processing in the main processor and directly uses its BLVDS signal for data transmission, saving costs and achieving a faster transmission rate.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for realizing long-distance transmission of KVM multi-channel audio, characterized by: include: Module A, module B, and the controlled host. Module A includes an FPGA, RJ45 interface 1, RJ45 interface 2, and RJ45 interface 3. Module B includes an RJ45, FPGA, MCU, and USB interface. The controlled host is bidirectionally connected to the USB interface of module B. The FPGAs of modules A and B both use the BLVDS interface for transmission. The transmission medium is a pair of differential lines, forming half-duplex communication. The communication signal is a BLVDS level signal. The RJ45 of module B is bidirectionally connected to the RJ45 interface 1 of module A. The FPGA of module A is used for audio decoding and output. The MCU includes an STM32F103C8T6 chip and its peripheral circuits, a crystal oscillator circuit, a reset circuit and a download circuit; The differential lines are connected to the IO ports of the FPGAs of module A and module B. To prevent signal interference and mutual interference between two adjacent pairs of differential lines, the P end of the differential line is set to pull up and the N end is set to pull down. The MCU of module B allows the controlled host to recognize the USB sound card device and transmits the audio data to the FPGA of module B using the SPI high-speed interface. The FPGA of module B uses the BLVDS interface to send the audio data or audio request to module A via the network cable. The data flow of module B is as follows: the FPGA of module B receives the audio request command and sends it to the MCU via the SPI1 host. The MCU interacts with the controlled host via the USB bus. The controlled host sends the audio data to the MCU. The MCU then sends the data to the FPGA of module B via the SPI2 host. The FPGA of module B sends the data to module A via the BLVDS interface. When multiple audio channels need to be transmitted simultaneously, module A can be connected to multiple modules B; The FPGA of module A converts the differential signal transmitted from module B into a single-ended signal through the BLVDS interface for processing. After serializing the multiple channels of audio data into one channel, the multiplexing of multiple channels of audio is completed. Then, the multiplexed multi-channel audio serial data is sent to the audio decoding module for decoding and playback at each aligned clock.

Images