Key words:
USB, interface design, embedded, video images, compression modules
Video image monitoring technology has been widely used. But in some special occasions, although there is no need for real-time image monitoring, there is a high quality of the quality of the image. For example, it is necessary to use the image picture as a remote video surveillance system, the quality of the image of the H.261 and H.263 images is unable to require high quality JPEG images. So research and design a static image compression module that meets industrial-grade requirements is very important for video image monitoring of special occasions. Be
In remote video surveillance systems, video acquisition and compression transmission is an indispensable integration. This article describes a JPEG video compression module design based on CY7C68013. It has 1.3 million pixel image resolution, compression ratio, simple interface, etc., which can be conveniently coupled with USB master devices, by the host computer Command control shot, video compression, and uploading compressed image data, thereby constituting a static video surveillance system.
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Hardware structure
This set of embedded video image compression modules developed herein, its hardware block diagram is shown in Figure 1. The host computer is an embedded intelligent industrial controller. It is the core processor with S3C4510B, which uses the ARM7TDMI RISC kernel to run Wince.Net 5.0 operating system. The lower machine consists of three main chips: CY7C68013, S1D13718 and K9650FB modules. CY7C68013 is a microprocessor integrated with USB 2.0, which integrates a USB 2.0 transceiver, serial interface engine (SIE), enhanced 8051 microcontroller and programmable peripheral interface, support USB1.1 and USB2.0 protocol. S1D13718 is an image engine chip and is responsible for JPEG codec. The video acquisition module uses the K9650FB module, which includes CMOS camera and image processing chip OV9650, and output images can range from 1.3 megapixels and have standard video interfaces and OmniVision customized SCCB configuration bus. The system hosting machine is constituted by a local area network to receive commands for remote monitoring systems and upload image data. The host machine transmits various types of shooting to CY7C68013 via the USB bus, and finally implements the initialization of SID13718 and K9650FB in the firmware program of CY7C68013, and take out the compressed JPEG image from the S1D13718 in-chip. Upload. Be
Figure 1 Hardware structure block diagram
software design
The USB software design in this design includes 3 parts: firmware programs, USB device drivers and applications. Be
Firmware program
The CY7C68013 firmware program is stored in the external EEPROM. The program is loaded to the 8051 core after power-on, mainly completing two functions: configuring the USB device and implements USB data transmission; implementation of the S1D13718 and K9650FB initialization. Be
The USB transmission method is divided into four types: control transmission, bulk transmission, synchronous transmission, and interrupt transmission. Considering the actual application environment and complexity, control transmission and batch transmission are used in the development. Control transmission is mainly used to complete the host's configuration and various control operations. Batch transfer is mainly used to complete image data transmission between the upper machine and the CY7C68013. The firmware program flow is shown in Figure 2. Be
Figure 2 Firmware program flow
Here, step 1 "It is mainly to complete the initialization of the USB interface, and step 6" can be seen as a task-making phase, complete USB transaction and user-specific tasks.
driver
Wince.NET's USB system software consists of two layers: the upper layer is the USB device driver layer, that is, the content studied herein; the bottom layer is the implementation of the USB function, including the host controller drive HCD and the USB protocol stack USBD two parts, this One level is provided by the Wince.Net operating system itself. Be
Two driving models provided by Wince.NET systems are native drivers and streaming drivers. The former is usually suitable for embossing into the platform, the latter is a general type of driver, suitable for equipment for most platform external connections. The flow port driver is characterized by the dynamic link library DLL at the user level to implement a set of fixed functions - flow port functions, which allows applications to access these drivers via file systems. This article uses a flow interface driver. Figure 3 illustrates the working structure of the flow port driver. The application calls the stream interface function via the file system, and then calls the native driver by the flow interface driver, or derived by the device manager and the system kernel or peripheral. Be
Figure 3 Work structure of the flow interface driver
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Writing the three entry functions of the USB bus device must be implemented under the Wi nce.net system USBDEVICEATTACH (), USBINSTALLDRIVER (), USBunInstallDriver (), this is the requirements of the USB protocol stack written by the Wince.net system, these three functions It also reflects the different writing characteristics of the USB bus device and other equipment drivers. After the device is connected to the host, the USB bus function implementation layer of the system underline will provide the detected device basic information and the information of the device to the upper layer, and a function of USBDeviceAttach () accepts this information to the client The next work of the driver is under the basis; in addition, the necessary registry items can be made better. In the WinCE.NET system, the configuration information of the device is stored in the system registry, so the necessary information about the specific device and some additional information can be registered in USBINSTALLDRIVER (), and the USBunInstallDriver () function is responsible for uninstalling these registration Equipment information. Be
A concise stream interface driver is definitely not open to the registry part. Here, we will add a registry file written by you to the kernel by adding a component. Here is the content of this registry file. Be
[HKEY_LOCAL_MACHINE \ Drivers \ USB \ LoadClients \ JPEG]
"Index" = DWORD: 1
"Prefix" = "jpeg"
// Equipment name is JPEG
"DLL" = "MyDriver.dll"
// Drive name, including the three inlet functions and DLL interface functions mentioned above mentioned
"ORDER" = dword: 0
When the peripheral is inserted, the system will automatically find if there is this item after obtaining the VID / PID. After the registry finds the driver DLL file, the USBINSTALLDRIVER function will first call it, the function uses USBD.DLL. Function registration device, and set the registry key based on the VID / PID, this item is not lost, the next insertion will be able to automatically find; if the VID / PID and the actual device of this function do not match, the USBINSTALLDRIVER is successful After that, the system calls the USBDEVICEATTACH function; there are three main implementations of the function:
(1) Allocate the device object structure, and use the device interface data on the system to fill in the device object structural member variable value, so as to transmit the device information in the flow drive function;
(2) Creating a thread that obtains the interrupt device data, registering the thread process;
(3) Call the ActivatedEvice () system function after completing the device object structure, and register the driver to the system to activate the device driver. Finally call the registerNotificationRoutine () function registration registration DeviceNotify function - this function is necessary, and call this function after the device is removed. Be
When the driver is loaded, the user program will return to the user program to the user program, so that the user program and the driver can be interacting. In this drive, all the operations of the S1D13718 and K9650FB modules are all incorporated by the DeviceIocontrol () function to JPEG_IOControl. Below is a partial driver.
Bool JPEG_IOCONTROL (DWORD HOPENCONEXT, DWORD DWCODE, DWORD * PBUFIN, DWORD DWLENIN, PBYTE PBUFOT, DWORD DWLENOUT, PDWORD PDWACTUALOUT)
{Switch (dwcode)
{
Case Cameral_Initial:
// Initialize the digital CAMERA interface
Break;
Case enable_jpeg:
/ / Enable JPEG module
Break;
Case Initial_JPEG:
// Initialize the JPEG module and start JPEG encoding
Break;
Case Read_JPEG
// read a picture
Break;
Else:
Break;
}
}
application
The host of this paper is developed using Win32 API in the Embedded Visual C ++ development environment. Due to the Win32 system, each external device can be abstract as file, the USB device can also operate as a system file, so the application call file operation API function can implement USB device communication with the driver. In this system, the CreateFile (), a closefile () function acquires or off, and the system control is performed with the device () function, the readFile () function is performed by the device control. Be
Conclusion
This article describes the USB interface design scheme of the embedded video image compression module, which can successfully perform picture capture of one frame of 1300 × 1028 per second, JPEG compression and upload under the USB1.1 protocol, and finally pass the picture through the Ethernet. Remote monitoring center, thereby constitute a static video surveillance system. This module has been implemented and applied in the anti-relief remote monitoring system.
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