Design of human-computer interaction module for UV LED irradiator

UV curing technology is a technology that uses short-wavelength ultraviolet rays to irradiate photocurable coatings to produce chemical reactions and bond components. Compared with ordinary thermal drying curing technology, UV curing technology has significant characteristics such as less thermal damage, fast hardening speed (usually about 1 s), and small deformation during the bonding process. It can protect sensitive components and therefore plays an important role in modern precision instrument manufacturing industries such as high-precision optical lens bonding and special instrument welding.
In the industrial application of photocuring, with the development of science and technology, the precision requirements for curing technology are getting higher and higher. With the development of LED manufacturing process and the maturity of high-power LED manufacturing technology, after the ultraviolet LED was developed, it has the characteristics of small wavelength range and stable and adjustable light intensity. Therefore, its application in photocuring technology has become a research hotspot. The ZUV series UV-LED irradiator of Japan's Omron Corporation has been successfully developed abroad. Its technical indicators are at the world's leading level, but its output power is fixed and the display mode is single, which cannot cope with complex industrial environments. The display module designed in this project is used in the human-computer interaction system of ultraviolet light curing control equipment. It not only has a static display interface of the output mode, but also has a real-time dynamic display interface of the irradiation power. It can be applied to a more intelligent ultraviolet LED irradiator human-computer interaction system to meet the needs of different environments in modern high-precision industry.

1 Implementation principle of human-computer interaction module
The implementation of human-computer interaction module requires the coordinated support of hardware and software, as shown in Figure 1. The call of display program is realized through the mutual coordination of state machine (state machine), also known as operation platform. The display program loads data into the display cache, and then the set display driver displays the content in the display cache on the LCD screen. Its working principle is shown in Figure 1.

1.1 Principle of hardware implementation
Software design is based on the hardware platform. The software needs the support of the hardware platform to play its role. Therefore, the design of the hardware platform must be implemented first. The display module of this project is applied to the control system of the ultraviolet LED irradiator. The system is mainly composed of a human-computer interaction unit, a data processing unit and a system control unit, a configuration information storage unit, a high-power LED driver power supply and a specially designed LED optical probe. The control core of the system is based on ADI's Blackfin531DSP processor, using a DSP+FPGA structure. The FPGA of the system is mainly used to collect key acquisition signals, realize SDRAM expansion, and drive the ultraviolet LED power supply; the DSP processor is mainly used to realize the drive and display of the human-computer interaction module. Therefore, the hardware principle of this project mainly involves the hardware part between DSP and LCD. The connection structure is shown in Figure 2.

The display module of the system uses SHARP's LQ043T3DX02 color LCD screen, which is driven by the PPI interface of DSP. PPI (Parallel Port Interface) interface is the parallel data interface of Black fin DSP processor, which is mainly used for high-speed data transmission. It includes 16-bit data line, 3 synchronization signals and a clock signal. PPI interface is directly integrated with DMA channel, and the data transmission width can be flexibly configured, supporting multiple data widths such as 8-bit, 10-16-bit, etc.
Since LQ043T3DX02 is a 24-bit color LCD, 8-bit data input for red, green and blue, and PPI has only 16-bit data output, the high 5 bits, high 6 bits and high 5 bits of red, green and blue are connected to PPI respectively, and the remaining 8 bits are always set low to form RGB-565 display mode. The effect of this display mode is almost the same as the real color.
1.2 PPI driver implementation
PPI driver mainly includes three parts: PPI setting, DMA setting and timer setting.
1) PPI setting
PPI provides a parallel port for LCD, making it easier to connect DSP and LCD. PPI supports two operating modes: ITU-R 656 and GP (General Purpose). The PPI interface of this project uses GP mode. In this design, the data in DSP is output to Sharp's LQ043T3DX02LCD through PPI, so the TX mode in General Purpose mode is used, and its internal frame synchronization has two. The clock signal of PPI is provided by FPGA. The function of frame synchronization signal is to control the sending timing of image data. The two frame synchronization pins are used to send HSYNC and VSYNC signals to LCD respectively. The driving timing of LCD is shown in Figure 3.

Because the LCD display switch control signal DISP of this project is provided by FPGA, the LCD switch control is indirectly realized by DSP controlling the value of the corresponding register in FPGA.
The PPI setting in this design is implemented as follows:
*pPPI_DELAY=65;
*pPPI_COUNT=320-1; //The number of bytes transmitted per line should be 1 less than the actual value 2)DMA setting
The DMA controller provides a channel for data transmission, so that data can be transferred between memories or between memories and peripherals with DMA functions. In the PPI drive application of this project, data needs to be transferred between the external 65MSDRAM external memory and PPI.
In this design, the specific DMA settings are as follows:
*pDMA0_X_COUNT=320:
*pDMA0_X_MODIFY=2; // Because each word is two bytes and its width is 2, it is set to 2
*pDMA0_Y_COUNT=262; // From the LCD DATA Sheet manual, we know that in the data transmission of the entire screen, the first 19 lines and the last 3 lines are invalid, which is required by the timing of the LCD screen, so 3+19+240=262. *pDMA0_Y_MODIFY=2:
3) Timer settings
In the 2-frame synchronization mode of PPI, the pins of Timer1 and 2 become PPI_FS1 and PPI_FS2 respectively. If PPI is set to transmit data, the timer must be set to generate the required output frame synchronization pulse. Usually in video applications, synchronization frame 1 is the HSYNC signal and synchronization frame 2 is the VSYNC signal. In this design, the specific DMA settings are implemented as follows.
*pTIMER1_PERIOD=406；//
Set the waveform time of the horizontal frequency. *pTIMER1_WIDTH=30；//Set the waveform width
of the horizontal frequency. *pTIMER2_PERIOD=262*406；//Set the waveform time of the vertical frequency.
*pTIMER2_WIDTH=406*1；//Set the waveform width of the vertical frequency.
*pTIMER1_CONFIG=EMU_RUN 1 CLK_SEL 1 TIN_SEL
1 PERIOD_CNT 1 PWM_OUT； *pTIMER2_CONFIG=EMU_RUN 1 CLK_SEL 1 TIN_SELIPERIOD_CNT 1 PWM_OUT；
//Use PWM_CLK for the clock counter. When timer1 and timer2 count the dot clock to the set number of times, a valid level will be output on the Out pin, and then the counter will start counting again.
*pTIMER_ENABLE=TIMEN1 1 TIMEN2; //Enable timer 1 and 2
1.3 Graphics standard library
The implementation of the user graphical interface requires the support of a rich software system in addition to the support of the hardware circuit module, and the most basic and indispensable one is the graphics standard library. The most basic library functions of the graphics standard library of the user graphical interface include simple drawing points, lines, and rectangles, and complex functions include filling rectangles, drawing circles, and placing bmp format pattern library functions. To realize the functions of displaying Chinese and English, it is necessary to design font functions. This system is based on the powerful VisualDSP++5.0Kernel (VDK) and has a powerful graphics library, so it can support complex user graphical interfaces.
To realize the user graphical interface, it is far from enough to have only the graphics standard library functions for drawing graphics. The graphics library can only form a single picture. However, if you want to form an operable graphical interface that suits user habits, you also need a powerful and stable operating system platform in the background, which determines the state of the system responsible for scheduling, which is what we usually call the state machine. The state machine determines the next state of the system according to the user's external key input and the current specific working state of the system, thereby calling the corresponding graphical interface. In this way, a humanized user graphical interface is realized to meet specific work requirements.

2 Software Design Ideas
For the design of the user graphical interface, it can be simply designed into a unified module. Considering the user's needs for the operation interface in complex application situations, we divide these interfaces into different categories. The design process is shown in Figure 4. One is a static configuration status display, and the other is a dynamic output status real-time change display. For the static interface, we can use the format conversion software to convert the bmp format image into a two-dimensional array and load it into the display cache to display the current fixed configuration interface.

Generally speaking, when programmers design dynamic display interfaces, if they follow conventional design methods, they will use some global variables as signs of different states and modes, so that the graphical interface can be changed. However, this will lead to too many variables, which will cause the combination of variables to increase exponentially. As the complexity of the work increases, the state transfer relationship will also increase dramatically, which will cause developers to fall into complex logical problems.
In order to solve the above problems, change the ordinary design method, set as few states as possible that can be changed, so that there are only one or two state quantities throughout the entire interface display system. If you want to get new interface information, you only need to change one or two specific state quantities. The solution in this article is to extract and parse key values ​​as the main line, and a small number of global variables and structures as auxiliary. The real system designed in this way is very concise and easy to control and modify. In the process of use, the corresponding interface is obtained by parsing the key values.
3 Experimental results
In the configuration status display, the display cache module plays a vital role. Changing the display cache can change the display interface. For the configuration status display interface, it is only necessary to call the pre-set bmp image into a two-dimensional array through the software, download it into the cache when the key value is activated, and then the driver will display the cache content on the LCD screen.
The configuration status display effect of the UV LED irradiator when working is shown in Figure 5.

When the illuminator is working and displaying dynamically, there is no need to frequently change the background elements such as the dialog box and the manufacturer's logo, while the output voltage and current values ​​are constantly refreshed, so the screen elements are divided into several pages for display. Page 1 displays the static background parameters, while the curve parameters and voltage and current values ​​are frequently refreshed. They are placed on page 2, and the contents of the two pages are simultaneously loaded into the display cache and output to the LCD by the driver. In this way, when the illuminator is working, it is only necessary to constantly change and call the contents of page 1 without changing the background parameters of page 1. Switch the display interface when there is keyboard operation.
The dynamic working status display effect is shown in Figure 6.

4 Conclusion
At present, the human-computer interaction module of UV irradiators at home and abroad is single, and it cannot meet some complex industrial needs in terms of integrity and user operability. Starting from the PPI interface driver of the Blackfin 531 processor of the UV LED control platform, based on the Visual DSP++5.0 software development environment, this paper designs a UV LED human-computer interaction display module. In practical applications, it successfully displays the configuration working status and output working status of the irradiator, making the control platform of the UV LED irradiator have a more intelligent human-computer interaction module.
In the future, with the domestic industrialization upgrade and the development of domestic high-precision industry, the demand for high-precision UV LED irradiators such as UV light curing welding products will become higher and higher. Therefore, the design of the Chinese character library of this human-computer interaction system will be the next focus of this topic.