#The4thInnovationContest#LEDElectronicWritingScreen

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* Briefly introduce the work:
        The structure of the LED dot matrix writing screen system is shown in Figure 1. Under the management of the controller, the LED dot matrix module display screen works in the scanning dim light that is not easily perceived by the human eye and the display lighting mode that is visible to the human eye; when the light pen touches the surface of the LED dot matrix module, the light pen first detects the scanning dim light of the LED point at the touched position to obtain its row and column coordinates, and then determines whether the LED at the coordinate is lit to a display state visible to the human eye based on functional requirements (as shown in Figure 1, the dark red LED point where the light pen touches has been lit), thereby realizing writing display functions such as "lighting, swiping, reverse display, whole screen erasing, stroke erasing, continuous writing of multiple words, object dragging" on the screen.
![QQ screenshot 20190531142720.jpg]
[Please fill in during the competition stage↓]
* 1. Details of the work;
PCB processing progress:
![image.png] Jialichuang is still good at production and can also produce the next side STM patch:
![image.png]
Use 74HC154 to drive the dot matrix screen column driver;
* 2. Describe the challenges faced by the work and the problems solved;
    1. How does the light pen light up the corresponding point?
    Solution: When writing, the dot matrix screen is initially slightly bright, and the photoelectric transistor collects light to light up the point. After processing by the main chip, the corresponding point is fully lit. The transistor is controlled to turn on, and the slightly lit transistor of the point is turned off at the same time. The specific method is shown in the hardware figure below.
![image.png]     2. Does the light pen use a transistor or an op amp?
Solution: According to personal preference, I generally use op amps as much as possible. Here, an op amp is used to build a comparator.
    3. How to convert the coordinates of the light pen?
Solution: The hardware uses 74HC595 to control four digital tubes, and the software part is shown below.
 I will just write a few points, and there are many more that I will not write.
* 3. Describe the key points involved in the hardware and software of the work;
Hardware part:
 ![image.png] The dot matrix part uses monochrome 16-pin, 1088BS common anode;
![image.png] Interrupt independent key circuit;
![image.png] Use 595 driver to save IO port, drive 4 independent digital tubes to display the current X-axis coordinate and Y-axis coordinate of the light pen and the current mode;
![image.png] Use LM393 op amp to build a comparator;
![image.png] Reserve the download interface of the MCU on the board;
![image.png] The minimum system board of the MCU;
![image.png] Software part:
header file and hardware IO pin definition:

![image.png] ![image.png] ![image.png] ![image.png] ![image.png] ![ image.png ] ![image.png] ![ image.png] ![image.png ] ![image.png] ![ image.png] ![image.png] 4. Upload pictures of the work; (The PCB must have the competition logo and take a photo to upload. If not, it will be deemed as giving up the competition) ![image.png] ![image.png] 5. Demonstrate your work and record it into a video and upload it; (The video content must include: work introduction; function demonstration; performance test; close-up of the competition logo on the PCB. Failure to do so will be deemed as giving up the competition)  ``` ```