CN201303348Y - Universal multi-serial bus converter - Google Patents

Abstract

The utility model relates to a control signal transmission system, in particular to a multi-serial bus conversion device. The universal multi-serial bus conversion device of the present utility model comprises a microcontroller, a USB interface unit, a CAN bus interface unit, an Ethernet interface unit, RS232 and RS485 interface units, wherein the USB interface unit, the CAN bus interface unit, and the Ethernet interface The units are respectively connected to the microcontroller through a parallel bus, and the RS232 and RS485 interface units are connected to the microcontroller through a photoelectric isolation device. The utility model enhances the compatibility problem of the network through the multi-serial port system, completely isolates the electrical interference between the device and the network, and has a wide range of applications.

Description

Universal Multiple Serial Bus Converter

technical field

The utility model relates to a control signal transmission system, in particular to a multi-serial bus conversion device.

Background technique

Most of the existing protocol conversion devices are for the conversion of two protocols, such as RS232 to CAN bus, RS232 to USB bus, etc. These conversion devices are only customized for specific applications and lack certain versatility. For applications where multiple different networks are controlled by a PC, the transfer rate between the conversion device and the PC is required to be greater than the rate of the controlled network, so that there will be no "bottleneck" phenomenon of the transfer rate. There are many kinds of existing network protocols, and sometimes multiple different networks are required to be seamlessly connected, or to achieve network expansion through access to third-party devices using various communication interfaces. Obviously, existing devices are difficult to meet the above-mentioned application scenarios and requirements.

Such as the Chinese patent application disclosed on January 16, 2008, the publication number is CN101105890A, which discloses a multi-serial bus system based on AT91M40800, which has CAN, Ethernet, RS485 and infrared remote control interfaces. RS232 is one of the most widely used communication protocols. Many serial devices use RS232 interface. At the same time, because the USB communication protocol has the characteristics of fast transmission rate and support for plug and play, the application of USB technology in embedded systems is increasing. more extensive. Obviously, this invention is difficult to support third-party devices using RS232 interface to access the network, nor does it support USB technology, and its versatility still has a certain lack.

Utility model content

The technical effects of the utility model can overcome the above defects, and provide a universal multi-serial bus conversion device, which integrates multiple communication protocol ports and has good versatility.

In order to achieve the above object, the utility model adopts the following technical scheme: it includes a microcontroller, a USB interface unit, a CAN bus interface unit, an Ethernet interface unit, RS232 and RS485 interface units, wherein the USB interface unit, the CAN bus interface unit, The Ethernet interface unit is connected to the microcontroller through a parallel bus, and the RS232 and RS485 interface units are connected to the microcontroller through a photoelectric isolator.

Described microcontroller unit adopts 16 single-chip microcomputers of the high-performance PIC24FJ128GA006 of Microchip Company, and the highest running speed reaches 16MIPS, has 128K ROM and 8K SRAM. This MCU comes with two UART ports, supports RS232 and RS485 communication modes, and can be used to expand the RS232 and RS485 interface units in this system, making full use of on-chip resources and saving peripheral devices, while improving the reliability of the module. According to the actual needs of each module, different data buffers are opened up for each port in the microcontroller. The working mechanism of the device is: each communication port is composed of a receiving task and a sending task, and each task is suspended or activated by a semaphore. When a port receives data, it sends the received data to the data buffers of the other ports, and at the same time sends a semaphore to the sending tasks of the other ports to notify that there is data in the buffer, and the sending tasks of the other ports receive the signal It is activated after the amount of data, and then the data in the buffer is sent to the network, thus realizing the data transmission between different networks, in which the USB port is used for the USB storage device, storing the data of the other communication ports or connecting the upper computer for realization The upper computer controls the rest of the network through the USB port.

The USB interface unit includes a USB controller and a USB socket, wherein the USB controller adopts CH375 of Biheng Electronics Company, supports USB1.1 and USB2.0 protocols, and can work in two modes of USB host and USB device. When working in the USB host mode, it is used to connect the USB storage device. Using the built-in firmware program, the microcontroller can realize various operations on it with only a few instructions, and is used to store the data transmitted through other ports of the device to the USB storage device. middle. When working in the USB device mode, it is used to connect to the host computer, which can realize the host computer to control different networks through the USB interface. The USB sockets include USB-A and USB-B sockets, which are respectively used to connect USB devices and USB hosts. The USB interface works in USB host or USB device mode with a jumper selection.

The Ethernet interface unit includes an Ethernet controller and an Ethernet transformer, wherein the Ethernet controller adopts a new independent Ethernet control chip CP2200 of Silabs Company, which integrates an IEEE 802.3 Ethernet media access controller (MAC) and 10BASE- T PHY, fully compatible with 100/1000BASE-T network, supports broadcast or multicast MAC addressing, the various integrated functions of CP2200 effectively reduce the load of the single-chip computer; the Ethernet transformer adopts the PRJ-010 transformer of the PRJ series, the transformer Integrated RJ45 network connector, with voltage isolation performance of more than 2kV.

The CAN bus interface unit includes a CAN bus controller, a CAN bus driver and a photoelectric isolation device, wherein the CAN bus controller adopts SJA1000 of Philips Company, supports the CAN2.0B communication protocol, and has a maximum communication rate of 1Mbit/s, and supports standard frames and extensions. Frame mode, photoelectric isolation selects high-speed device 6N137.

The RS232 and RS485 interface units are implemented by the microcontroller with its own UART communication module and externally connected with MAX232 and MAX485 level converters, and in addition there are photoelectric isolation devices. The UART mode of the microcontroller is used to make full use of the on-chip resources and save peripheral devices, and the high-speed device 6N137 is selected for photoelectric isolation.

The configuration software on the PC side is implemented by VC, which can configure CAN bus, Ethernet, RS232 and RS485.

The utility model has multiple uses, and can be used for the interconnection between multiple different networks or controlling multiple networks through a PC and realizing network expansion through accessing third-party devices with different interfaces, and has certain versatility. The device can be selected to enter the configuration mode or the normal operation mode through the jumper. In the configuration mode, connect the configuration software in the PC through the RS232 port of the device, and configure the parameters of CAN bus, Ethernet, RS232 and RS485 and the data exchange mode between each network. The configuration software in the PC is realized by VC. Through the configuration of CAN bus, Ethernet, RS232 and RS485, the working parameters of these three ports can be selected arbitrarily, so that the device can work in various occasions. In addition, the USB interface can be selected to work in host mode or equipment through jumpers mode, greatly improving the versatility of the device.

The CAN bus interface unit, RS232 and RS485 interface units are connected by photoelectric isolation devices, which prevents the interference in the network from entering the conversion device and ensures the reliability of the work. The device is powered, and the electrical interference between the network and the device is completely isolated.

The real-time operating system uC/OS-II is embedded in the microcontroller, which is a priority-based preemptive multi-task real-time kernel, and each task in the system is event-driven. In the device, each port is responsible for communication by a sending task and a receiving task, and each task is started or suspended by a corresponding semaphore control. The semaphore of the receiving task is sent by the receiving interrupt program of the corresponding port, and the semaphore of the sending task is sent by other ports after storing the received data into the data buffer of this task. By implanting the uC/OS-II system, the system runs in multi-task mode, which greatly improves the real-time performance of the system.

The RS232 and RS485 interface units are realized by the on-chip UART communication module and a small amount of peripheral circuits, making full use of on-chip resources, saving peripheral devices, and increasing system reliability.

The utility model enhances the compatibility problem of the network through the multi-serial port system, completely isolates the electrical interference between the device and the network, and has a wide range of applications.

Description of drawings

Fig. 1 is a structural block diagram of the utility model.

Detailed ways

The USB interface unit U2 adopts CH375 as the USB bus controller, and the U2 TXD pin is grounded for selecting the parallel bus working mode. The U2 data bus D[7:0] is connected to the microcontroller U1 address/data multiplexing bus PMA[7:0]/PMD[7:0], the U2 chip select signal CS is connected to the U1 chip select output pin PMCS1, and the command /Data selection signal A0 is connected to U1 address bit PMA3, when CS is valid and A0 pin is high level, select the command port, and you can write commands; when CS is valid and A0 pin is low level, select the data port, you can read and write data , all operations are composed of command codes and several input or output data, and some commands do not require input data or have no output data. A0=1 writes a command to the command port, then A0=0 writes or reads data. The U2 interrupt output signal INT is connected to the U1 external interrupt input pin INT1, and the read and write control signals WR_N and RD_N are respectively connected to the U1 read and write signals WR and RD.

The software design mainly includes the initialization of CH375, and the operation of receiving and sending data when the device works as a USB host and a USB device. Select USB to work in host or device mode by a jumper. When working as a USB host, the built-in firmware of the CH375 that handles the Mass-Storage mass storage device's dedicated communication protocol can automatically detect and identify the connection of commonly used USB storage devices including USB hard disks and USB flash drives. Using CH375 dedicated built-in firmware, the microcontroller can directly read and write USB storage devices with sectors as the basic unit. When working as a USB device, use the built-in firmware mode of CH375 to automatically detect the connection of the USB host. The specific working mechanism is: when working as a USB host, if a USB storage device is detected, the microcontroller will create files named CAN.txt, Ethernet.txt, RS232.txt, and RS485.txt respectively in the storage device. It is used to store the data in the corresponding port, and the storage format is hexadecimal; when working as a USB device, if the data downloaded from the USB host is received, the received data is first stored in the buffer of each port, and then sent to each port. The port sends a semaphore to inform the data buffer that there is data, and each port sends the data in the buffer to the network after receiving the semaphore, thus realizing the connection of the PC to different networks through the USB interface.

Described CAN bus interface unit adopts SJA1000 (U3) as CAN bus controller U3, U3 address/data multiplexing bus interface AD[7:0] and U1 address/data multiplexing bus PMA[7:0]/PMD[7 :0] connected, the address latch input signal ALE is connected to the U1 address latch output signal PMA0, which is used to separate address and data information. The chip select input pin CS is connected to the U1 PMA4 pin for chip selection, the U3 interrupt output pin INT is connected to the U1 external interrupt input INT2, and the read and write control input signals are respectively connected to the U1 read and write control output signals RD and WR. U3 has a total of 32 registers. The microcontroller realizes the control of the CAN bus through the read and write operations of these registers. The read and write of these registers by the microcontroller is the same as the operation of the on-chip registers. CAN bus driver U7 adopts PCA82C250. There is a photoelectric isolation circuit between U3 and U7 to prevent the interference in the CAN network from entering the device. The DC/DC power isolation module supplies power to the photoelectric isolation and U7, so that the device is completely isolated from the CAN network electrically. .

The software design includes CAN bus initialization, data sending and receiving. CAN bus initialization includes working mode, receiving filtering mode, receiving mask register, baud rate parameter setting, and interrupt enable register parameter setting, among which the receiving filtering mode, receiving mask register and baud rate parameter setting can be freely set by the PC-side setting software , here it is just initialized to the default settings. The interrupt enable register enables the receiving interrupt and error interrupt, and checks the cause of the error after entering the error interrupt. If it is a sending or receiving error, then clear the corresponding flag and return. If it is a bus error and the error counter value is greater than 255, then Reset the bus. The default sending method is to send standard frames, and the ID of all sent frames is 0, which can be set to send standard frames and extended frames with fixed IDs or standard frames and extended frames whose IDs are provided by the first two bytes in the sending buffer. When the sending task receives the buffer full semaphore, it sends the data in the buffer according to the preset settings. The default receiving method is to receive and forward the data fields in all frames, that is, the received data is not filtered. It can be set to filter receiving method, and only receive frames whose ID is consistent with the filter register. At the same time, it can be set whether the forwarded data includes the ID of the received frame. Before the receiving interrupt returns, store the received data into the data buffers of the remaining ports respectively, and then send a semaphore to each port sending task to notify that the buffer has data, and the sending tasks of the other ports receive the semaphore Then send the data in the respective buffers to the respective networks according to the preset settings. The default baud rate is 500Kbps, which can be set to any baud rate between 10K-1000K, but the set baud rate must be consistent with the connected network to work properly.

The Ethernet interface unit adopts CP2200 as Ethernet controller U4, U4 address/data multiplexing bus A[7:0]/D[7:0] is connected to U1 address/data multiplexing bus PMA[7:0]/ PMD[7:0], U4 chip select pin CS is connected to PMA5 pin of microcontroller U1, U4 interrupt output signal INT is connected to U1 interrupt input signal pin INT3, U4 address latch input pin ALE is connected to U1 address latch The output pin PMA0, the U4 read and write input pins RD_N, WR_N are respectively connected to the U1 read and write output pins RD, WR, and the U4 bus multiplex enable pin MUXEN is connected to the high level of VCC to select the multiplex bus working mode.

The software design of the Ethernet interface unit includes the realization of the TCP/IP protocol stack and the design of the main application program. Due to the variety of TCP/IP protocols, considering the actual requirements and resources of the embedded system, it is impossible and unnecessary to implement all protocols of TCP/IP. After tailoring the TCP/IP protocol, ARP, ICMP, IP, TCP, UDP protocol module. The protocol implemented in this system is based on Microchip's TCP/IP protocol stack. The protocol stack is a collection of different modules. When a certain type of packet is received, the corresponding protocol module (IP, TCP, UDP, ICMP, ARP ) to complete the processing of each module. In order to reduce the burden of the main application program to manage each module, the protocol stack uses a special application layer module called "StackTask". "StackTask" is implemented in a cooperative task processing mode. After being given a processing time, it will poll the MAC layer for valid data packets. If a packet is received, it will be decoded and routed to the corresponding module for the next step processing.

The main application program includes CP2200 initialization, data reception and transmission. Initialization includes the interrupt enable register, initializes the physical layer, configures the IOPWR register, is used to set the Activity and Link LED indicators, initializes the MAC layer, configures the selection of the receiving filter and the working mode, and makes the initialized CP2200 ready to receive and send data. Data reception is generated through an interrupt. Once a data packet is received, CP2200 will generate an interrupt to notify the microcontroller U1. The microcontroller U1 can read the data packet with the automatic read interface, or skip the packet by setting RXSKIP1. . The CP2200 provides a simple interface for sending Ethernet packets, the microcontroller U1 only needs to load the source and destination addresses, length/type and data into the send buffer, all other parts of the Ethernet frame such as preamble, frame start delimiter , CRC padding are all produced automatically. The data sending task is activated by the receiving operation sending semaphore of the other ports.

The RS232 and RS485 interface units are realized by using a built-in UART module of the microcontroller U1 and external level converters MAX232 and MAX485. The built-in UART module of the microcontroller U1 supports RS232 and RS485 modes, and supports a baud rate range of 15bps-1Mbps. A photoelectric isolation device is used between the level converter and the microcontroller U1 to completely isolate the electrical interference between the device and the network.

The software design includes port initialization, data receiving and sending. The initialization process includes configuring the interrupt enable register, baud rate, data bits, stop bits, and parity check bits. The default settings are used for initialization, the baud rate is 9600bps, 8 data bits, 1 stop bit, and no parity bit. These parameters can be set by PC through setting software. Send tasks are activated by receive tasks on the remaining ports. When a receiving interrupt occurs, the data is stored in the buffers of the other ports, and then a semaphore is sent to activate the sending tasks of the other ports, so that the data received in this network is sent to other networks, and the communication between different networks is realized. interact. In addition, the RS232 interface can be connected to third-party equipment with RS232 interface, which greatly facilitates the application of RS232 equipment to realize network expansion.

Claims (9)

1. a general multi-serial bus conversion device is characterized in that comprising microcontroller, USB interface unit, CAN bus interface unit, Ethernet interface unit, RS232 and RS485 interface unit, wherein USB interface unit, CAN bus interface unit, The Ethernet interface unit is connected to the microcontroller through a parallel bus, and the RS232 and RS485 interface units are connected to the microcontroller through a photoelectric isolation device. 2. The universal multi-serial bus conversion device according to claim 1, wherein the microcontroller adopts the PIC24FJ128GA006 model. 3. according to claim 1 and 2 described universal multi-serial bus converting devices, it is characterized in that the USB interface unit comprises a USB controller and a USB socket; The working mode can be selected through the cable; the USB socket includes two sockets, USB-A and USB-B, which are used to connect USB devices and USB hosts respectively. 4. universal multi-serial bus conversion device according to claim 3, is characterized in that USB controller TXD pin grounding is used for selected parallel bus mode of operation; The data bus D pin of USB controller is connected to microcontroller The address/data multiplexing bus PMA/PMD pin; the chip select signal CS pin of the USB controller is connected to the chip select output pin PMCS1 pin of the microcontroller; the command/data selection signal A0 pin of the USB controller is connected to The address bit PMA3 pin of the microcontroller; the interrupt output signal INT pin of the USB controller is connected to the external interrupt input INT1 pin of the microcontroller; the read and write control signals WR_N and RD_N pins of the USB controller are respectively connected to the microcontroller The read and write signals WR and RD pins are connected. 5. according to claim 1 and 2 described universal multi-serial bus conversion devices, it is characterized in that CAN bus interface unit comprises CAN bus controller, CAN bus driver, photoelectric isolator, between CAN bus controller and CAN bus driver It is connected through a photoelectric isolator; the CAN bus controller adopts the SJA1000 model; the CAN bus driver adopts the PCA82C250 model. 6. universal multi-serial bus conversion device according to claim 5, is characterized in that the address/data multiplexing bus interface AD of CAN bus controller links to each other with the address/data multiplexing bus of microcontroller; CAN bus controller The address latch input signal ALE pin of the microcontroller is connected to the address latch output signal PMA0 pin of the microcontroller; the chip select input CS pin of the CAN bus controller is connected to the PMA4 pin of the microcontroller for chip selection; the CAN bus control The interrupt output INT pin of the controller is connected to the external interrupt input INT2 pin of the microcontroller; the read and write control input signal pins of the CAN bus controller are respectively connected to the read and write control output signal RD and WR pins of the microcontroller. 7. according to claim 1 and 2 described universal multi-serial bus switching devices, it is characterized in that the Ethernet interface unit comprises the Ethernet controller and the Ethernet transformer that are connected to each other; Wherein the Ethernet controller adopts the CP2200 model; Ethernet The transformer adopts the model PRJ-010, which integrates the RJ45 network connector. 8. universal multi-serial bus switching device according to claim 7, is characterized in that the address/data multiplexing bus A/D of ethernet controller connects the address/data multiplexing bus PMA/PMD of microcontroller; The chip selection CS pin of the network controller is connected to the PMA5 pin of the microcontroller; the interrupt output signal INT pin of the Ethernet controller is connected to the interrupt input signal INT3 pin of the microcontroller; the address latch input of the Ethernet controller The ALE pin is connected to the address latch output PMA0 pin of the microcontroller; the read and write input RD_N and WR_N pins of the Ethernet controller are respectively connected to the read and write output RD and WR pins of the microcontroller; the bus of the Ethernet controller The MUXEN pin is connected to the high level of VCC to select the working mode of the multiplexing bus. 9. The universal multi-serial bus conversion device according to claim 1 or 2, characterized in that the RS232 and RS485 interface units are respectively connected with the UART communication port of the microcontroller through a photoelectric isolator.

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