RU2243589C1 - Method for transferring data via computer network from device provided with usb interface - Google Patents

Abstract

FIELD: computer engineering.

SUBSTANCE: computer is provided with software block, by means of which inside computer, at moment of user application query to device with USB interface, I/O queries are intercepted and sent through network card and network to device with USB-host functions. As said device a remote host-controller is used, by means of which in accordance of received query data exchange with device with USB interface is organized.

EFFECT: higher speed of operation.

3 cl, 4 dwg

Description

The invention relates to the field of computer technology. It can be used to obtain digital still and video images in control systems for production processes, scientific experiments, video surveillance systems, etc.

Known CCTV system (US patent No. 6323897), consisting of several special network cameras and several special monitors. Camcorders and monitors are included in the computer network. Both camcorders and monitors have different network addresses in accordance with the network protocol IP (Internet Protocol). Each camera generates an encoded stream of video data, places it in accordance with the network protocol in an IP packet and sends it to the network. Devices included in this network receive, save video data, and also form video images from video data.

The disadvantage of this system is that it uses only highly specialized expensive devices. In this system, it is impossible to directly use video cameras for personal computers that have a USB interface (Universal Serial Bus - universal serial bus). USB is the industry standard for expanding the architecture of personal computers (PCs) (see Compaq, Intel, Microsoft, NEC, Universal Serial Bus Specification, Revision 1.1, September 23, 1998). USB provides data exchange between the host computer and many peripheral devices. The entire USB system is controlled by the host controller. The bus allows you to connect, configure, use and disconnect peripherals with a USB interface while the computer and the devices themselves are running. The host controller is the only master device that controls the data exchange, and all devices connected to the bus are exclusively slave devices. Devices with a USB interface can perform some function, for example, form a video image as a PC camera or a device for digitizing a television signal, or provide additional connection points to the bus, in this case the device is called a hub. On the one hand, the hub is connected via USB to the host, and on the other hand, up to 4 other devices with a USB interface can be connected to the hub. The program-logical topology of the USB bus is simpler than the physical one: the host exchanges information with the devices as if all devices are connected directly to the host controller.

Video cameras with a USB interface are produced in bulk quantities by many manufacturers, are widely used for video conferencing, equipped with a large amount of free software (software) and have a cost 10-20 times less than special network video cameras. However, these PC cameras can only be connected to a computer network through a computer to which they are connected via USB, the maximum length of which is 5 meters.

A known method of connecting devices with a USB interface to a personal computer, which allows to increase the distance from the computer to the USB device from 5 to 100 meters (US patent No. 6381666). This method uses two devices: a local extension cable (LEX) with a USB interface that connects to a computer, and a remote extension cable (REX) that acts as a USB hub to which a USB device is connected. Digital data in the form of USB IN, OUT, DATA, etc. packets are transmitted between these two devices over unshielded twisted pair cables. HANDSHAKE packets are generated by the devices themselves to meet the USB time limit requirements.

The disadvantage of this method is that it is not fully networked, since it allows you to transfer data from a USB device to only one computer.

The closest adopted for the prototype is a method of connecting USB devices to a local computer network (US patent No. 6389029), which also uses two special devices. The first device has, on the one hand, a USB interface for connecting to a USB host controller located inside the computer and, on the other hand, a network interface for connecting to a local computer network. The second device has, on the one hand, a network interface, and on the other hand, a USB hub for connecting devices equipped with a USB interface to it.

In the indicated connection method, data from the computer is received by the first device, processed according to the USB bus time limitations according to the USB protocol, packaged in an IP packet equipped with the IP address of the first device as the sender and the IP address of the second device as the recipient. The packet is sent to the local network through network hubs (network hubs) - devices that have several network inputs (ports) for connecting computers and network devices. Network hubs provide data transmission over a computer network. The second device with the functions of the USB hub extracts the USB protocol data from the received IP packet and transfers it to the USB device. When transferring data from a USB device to a computer, the second device processes the received USB data in accordance with the USB protocol, packs it into IP packets and sends it to the first device, which extracts it from the package and transfers it to the computer via the USB bus. Thus, packets IN, OUT, SETUP, DATA are transmitted. At the same time, IP packets can be transmitted without limiting the distance due to the use of network hubs that relay IP packets. The specified method is proposed for transferring asynchronous data between computers and devices equipped with a USB interface.

Due to repeated conversions, the overall data transfer speed from devices equipped with a USB interface slows down. In addition, this method cannot be applied for the transfer of isochronous data, for example, video data from a PC video camera. Any delays in the transmission of IN token requests from the computer to the PC camera over the local network cause a failure in the video stream and the inability to further decode it and display the video image on the monitor screen.

The present invention is based on the task of developing a method for transmitting data via a computer network from a device equipped with a USB interface, which provides an increase in the data exchange rate by reducing the number of data conversion steps.

The problem is solved in that in a method for transmitting data via a computer network from a device equipped with a USB interface, namely, that a device equipped with a USB interface transfers I / O requests from one of the computers included in the network through a device with USB host functions information placed in an IP packet, which is also equipped with the network IP address of this computer as a sender, and when transmitting data to a computer from a device equipped with a USB interface, a device with USB host functions processes the data received they are given data in accordance with the USB protocol, puts them into IP packets and sends them through a computer network to a computer, according to the invention, the computer is equipped with a software unit with which, at the time of the user program accessing the USB device, they intercept input requests / output and direct them through a network card and computer network to a device with the functions of a USB host, which is used as a remote host controller, with which, in accordance with the received request, anisyl data exchange with a device equipped with a USB interface.

In the proposed method, there is no data conversion in the host controller of the computer, their transfer via USB to the first device (in the prototype method), the exchange of confirmation packets or requests for retransmission and other actions specified by the USB protocol. Instead, input / output requests from the USB device driver are transferred to the computer network directly by the computer using the software unit, and the remote host controller interacts with the device equipped with the USB interface. Since the computer processor has much greater computing power, redirecting I / O requests to the network is faster than transmitting them to the built-in host controller, then via the USB bus to the device sending them in a converted form to the network.

If the device with the USB interface, for example, a PC-video camera or a device for digitizing a television signal, uses the isochronous transmission method, that is, the requirements for the transmission speed are especially stringent, the video data of each USB frame is placed in a separate IP packet.

The broadcast IP address can be specified as the destination IP address in the IP packet. In this case, any computer on the network can receive video data. Protection against unauthorized viewing in this case is carried out at the client software level.

The proposed method allows you to include in a computer network several video sources, view and accumulate video data on several computers, which increases the reliability and information content of the video surveillance system.

In the future, the invention is illustrated by specific examples of its implementation and the accompanying drawings, in which:

figure 1 depicts the architecture of a computer network with a device equipped with a USB interface;

2 is a block diagram of a device with USB host functions;

figure 3 is a sequence of USB packets on the USB bus during isochronous transmission of video data;

4 is an example of connecting video devices with a USB interface to a computer network.

The proposed method for transmitting data over a computer network from a device equipped with a USB interface is as follows.

Using the program unit installed inside the computer 1 (Fig. 1), at the time the user program accesses the final (functional) device 2 equipped with the USB interface, the I / O requests addressed to the USB host driver are intercepted, encoded and sent via the network interface, for example, an Ethernet 100TX network card 3, through a network hub 4 of a computer network 5, to a device with USB host functions, using a remote host controller 6. In this case, in the header as the recipient address The chute indicates the IP address of the device with the functions of a remote USB host, to which a functional (terminal) USB device called by the client software is connected.

Module 7 (Fig. 2) of the network interface of the device with USB host functions extracts the IP packet from the received Ethernet network packet and places it in the random access memory 9 (RAM) through the microcontroller 8. The analyzer 10 headers of the IP packets allocates the network IP address of the computer that sent the I / O request, and places it in the reprogrammable read-only memory 11 (EPROM). The I / O request analyzer 12 decodes the request, selects the program corresponding to the request in the EEPROM 11, and transfers the program start address to the USB 13 host controller through the microcontroller 8. The host controller 13 performs all actions according to the USB protocol, including sending reset signals and SOF, SETUP, IN, OUT, DATA, ACK packets on the bus. In accordance with the device driver program developed by the manufacturer, the device 14 is configured and data reception / transmission is organized. In this case, the data to be sent to the computer software is transmitted via microcontroller 8 to RAM 9. Then, microcontroller 8 places this data in the IP packet data area, and microcontroller 8 places the address of the computer that sent the request in the recipient address field in the IP packet header. which is stored in the ROM 11.

When using a USB video device as a device equipped with a USB interface, the video data from each USB-frame of which, when transferred to a computer, is placed in a separate IP-package.

If necessary, by a special command when transmitting the video data stream, the broadcast IP address is placed in the address field of the header recipient, which makes it possible to receive video data by any computer connected to the network.

Figure 3 shows the sequence of passage of USB packets on the USB bus in the case of isochronous reception of video data from the device. The total duration of one USB frame is determined by the time interval between the SOF (Start of frame) packets and is equal to 1 millisecond. SOF and IN packets have a duration of several microseconds. The DATAO package with video data may have a different size, set by software. At the maximum speed of the PC camera, this size is about 900 bytes, and its duration is about 700 microseconds. Thus, at the end of each USB frame there is a time interval during which the accumulated data is transferred from the buffer located in RAM to the computer network. Since the speed of data transfer on the Ethernet network is an order of magnitude higher than the speed of the USB bus, this time is enough to free the buffer and prepare for the next DATAO packet.

Figure 4 shows an example of a video surveillance system using the proposed method for connecting video devices. As the stations for monitoring and archiving video images, personal computers 15 based on the Intel Celeron processor 1700 MHz, with 256 MB DDR RAM, and a 60 GB hard drive were used. Realtek 16 Ethernet 100TX network cards are installed on computers 15. Computers 15 and three USB 17 host cocktrollers are connected to the Som network hub 18 using a fifth category cable 19, which has two unshielded twisted pairs of wires. Using a USB 20 bus, a Maxxtro PC video camera 21 is connected to one of the USB 17 host controllers, a Creative PC video camera 22 is connected to another USB 17 host controller, an Aver video capture device 23 is connected to the third USB 17 host controller, which is connected to the SONY home video camera 24.

Tests have shown the stable operation of PC-cameras in the mode of 15 frames / second, a resolution of 640 × 480 pixels and the simultaneous operation of the video capture device in the mode of 320 × 240 pixels, 25 frames / second.

Claims (3)

1. A method of transmitting data via a computer network from a device equipped with a USB interface, namely, that a device equipped with a USB interface transfers information input / output requests placed in IP from a computer with a USB host function through a device with USB host functions a package that is also equipped with the network IP address of this computer as the sender, and when transmitting data to the computer from a device equipped with a USB interface, a device with USB host functions processes the data it receives in accordance with the protocol USB, puts them in IP packets and sends them through a computer network to a computer, characterized in that the computer is equipped with a software unit with which, at the moment the user program accesses the device equipped with the USB interface, they intercept I / O requests and send them through the network a card and a computer network to a device with the functions of a USB host, which is used as a remote host controller, with which, in accordance with a received request, data exchange with the device is organized, USB interface. 2. The method according to claim 1, characterized in that as a device equipped with a USB interface, a USB video device is used, the video data from each USB frame of which, when transferred to a computer, is placed in a separate IP packet. 3. The method according to claim 2, characterized in that when transmitting video data, the broadcast IP address is indicated in the IP packet as the recipient's IP address.

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