O Introduction
In order to meet the needs of the CCTV (closed circuit television) security industry to generate text and images and superimpose them on video images, MAXIM has launched the MAX7456 video subtitle module. The device is a single-channel, monochrome on-screen display (OSD) generator with built-in non-volatile memory (EEPROM). The device can generate user-defined OSD and insert it into all functions required by the video signal, and is compatible with NTSC and PAL video standards. This article discusses the realization process of the monochromatic OSD system based on MAX7456 with examples.
1 The internal structure of MAX7456
The MAX7456 integrates all functions and EEPROM required to generate a user-defined OSD and insert it into a composite video signal. The device has built-in input clamp, synchronization generator, video timing generator, OSD insertion MUX, non-volatile (EEPROM) character memory, display memory, OSD generator, crystal oscillator, SPI compatible interface for reading / writing OSD data And video drive. The internal structure of the MAX7456 chip is shown in Figure 1.
The MAX7456 can provide functions such as blinking, reverse color, and background control. At the same time, the MAX7456 can accept signals common in the security industry video standards such as standard NTSC or PALCVBS. Therefore, the device can be adapted to the needs of most security markets.
2 OSD module system structure
Using the MAX7456 single-channel OSD generator will greatly reduce the complexity and cost of the OSD system. The system only needs a common microcontroller chip and the corresponding software to realize the flexible display of subtitles. Figure 2 shows the block diagram of the MAX7456 application system. In the figure, the PC can download the font information generated by the software to the microcontroller (MCU) through RS232 (serial port), and the font information is stored by the microcontroller (MCU) through the SPI (Serial Peripheral Interface Bus) interface to the MAX7456. EEPROM. After the analog video signal output by the camera is processed by the OSD module, the required subtitled image can be obtained. The software running in the microcontroller can control the display content of the subtitles in real time through the SPI interface.
3 OSD module hardware structure
As the core component of OSD system, MAX7456 needs the cooperation of corresponding peripheral devices to play its role. Figure 3 shows the block diagram of the hardware structure of the OSD module. Among them, MAX74 56 is responsible for adding caption processing to the input analog video signal; MAXQ2000, as a low-voltage micropower microcontroller, can provide corresponding control signals for MAX7456 through the GPIO analog SPI interface timing, and is responsible for communicating with the PC through the serial port Obtain user-defined character set and configuration information; MAX3002 is a bidirectional level conversion chip, which can convert the 2.5V system signal of MXXQ2000 into a 5V system signal that MAX7456 can use; MAX3311 is a serial chip supporting MAX02000 Provide serial port signal for communication with PC; MAX8881 can convert 5V power supply to 2.5 V power supply required by single chip microcomputer and buffer chip.
4 Software structure of OSD module
The software that works with the OSD module includes two parts: one part is the firmware running in the microcontroller, it includes the SPI interface driver, memory configuration program, register configuration program, serial port transaction communication, etc .; the other part is the user interface running on the PC side , Can provide users with easy OSD settings and memory upgrade function.
4.1 MAX7456 control routine
The MAX7456's SPI interface can support up to 10 MHz interface clock (SCLK). When writing to the register, pull low
The serial interface can be enabled to read data from SDIN on the rising edge of SCLK; and when When it goes high, the data is latched into the input register. If during transmission If it becomes high, the program terminates (that is, the data is not written to the register). After going low, the device will wait to read the first byte from SD-IN to determine the type of data transfer being performed. Figure 4 shows the timing of writing data. 
When reading the register, pull low
. The address will be latched into SDIN on the rising edge of SCLK. Data can then be output from SDOUT on the falling edge of SCLK. Figure 5 shows the timing of reading data from the device. 
The following is the specific operation method code:
4.2 PC user interface
The software on the PC can provide users with common OSD configuration information, such as video format selection, subtitle brightness, flip mode, flashing, and selection of subtitle files. Figure 6 shows the user interface diagram.
In this way, through the software, users can also edit the subtitle display content, customize the character set and set the OSD background color.
4.3 Compile development environment
IAR EmbeddedWorkbench 2.10A running on the Windows platform is one of the integrated development tools specially used for MAXO series microcontrollers, and has been used by most MAXQ series chip development. However, after creating a new project under IAR, you also need to set the compilation options: General OpTIon / Target / Device and select MAX200X.
5 Conclusion
The MAX7546 is a single-channel, monochrome on-screen display (OSD) generator. Using it to develop an OSD system can not only greatly save board space and design time, but also provide higher performance at a lower cost. This article introduces the basic structure of the OSD system, and explains the technical points of using the MAX7456 to build an analog TV caption on-screen display system from both hardware and software aspects, hoping to play a guiding role for OSD system developers.
About Esco Bars 2500 Puff Disposables
White Horse Vapor offers the best collection of Pastel Cartel Esco Bar Disposables out there. Each 2500 puff Pastel Cartel Esco Bars Disposable Vape pen features a 6mL prefilled e-liquid capacity and a huge 1000mAh battery! Every disposable vape pen in this collection comes in 50mg (5%) nicotine strength. This 2500 Puff Bar provides unmatched flavor in every puff thanks to the mesh coil design and quality vape juice flavors available. The newly introduced flavors for these 2500 puff Pastel Cartel Esco Bar disposables are Blue Raspberry, Banana Ice, Watermelon Ice, Pink Lemonade, Bubblegum Ice, Strawberry Ice, Spearmint, Red Apple, Peach Ice, and more!
Escobars,esco bar flavors,Esco Bar Disposable,Esco Bar vape.
Hongkong Onice Limited , https://www.ousibangvape.com