Design of LED dot matrix display control system based on PIC32 single chip microcomputer

Introduction: LED dot matrix display is a large display system that integrates microelectronics technology, computer technology, and information processing technology. It has become an ideal choice for many display media and outdoor work displays due to its bright colors, wide dynamic range, high brightness, long life, stable and reliable operation, etc.

Introduction: LED dot matrix display is a large display system that integrates microelectronics technology, computer technology, and information processing technology. It has become an ideal choice for many display media and outdoor work displays due to its bright colors, wide dynamic range, high brightness, long life, stable and reliable operation, etc.

Background of the project:

LED dot matrix display is a large display system that integrates microelectronics technology, computer technology, and information processing technology. It has become an ideal choice for many display media and outdoor operation displays due to its bright colors, wide dynamic range, high brightness, long life, stable and reliable operation, etc. At present, it has been widely used in many industries such as military, stations, hotels, sports, news, finance, securities, advertising, and transportation.

At present, there are two main types of LED dot matrix display control systems: built-in fonts; PC controlled via RS232 or RS485 bus. In the first system, the character code needs to be stored in the microcontroller (including the memory it controls) or saved in a dedicated control card in advance, so each time the font is modified, it needs to be reconnected to the PC for downloading, which is troublesome; the second system can modify the font in real time, but it also needs the help of a PC. The above two solutions cannot meet the needs of field display because they are inseparable from the PC.

With the development of the transportation industry, tourism industry, and advertising industry, the LED dot matrix display propaganda prompt text has been required to be changed in real time and anywhere. The traditional LED dot matrix display control system obviously can no longer meet this demand. Therefore, we designed a new LED dot matrix display control system based on PIC32 single-chip microcomputer. In this system, we have defined a character library by ourselves. With the powerful functions of the PIC32 series of single-chip microcomputers, this system integrates the character generation LED dot matrix code software inside the control module. According to the concise character comparison table specified by itself, any character number is input from the keyboard. After the system recognizes it, it generates the LED dot matrix display code corresponding to the character in real time, and stores the code for display. At the same time, the generated code can also be stored in the U disk according to the address code set by the user, so that each segment of text information can be stored in the U disk according to different address marks. Subsequently, this U disk can provide a font source for other LED dot matrix display systems controlled by low-end MCUs, and users can select the required text information according to the address, realizing the multiplexing control of the U disk. This system can completely get rid of the dependence of the LED dot matrix screen on the PC and can be well used for LED dot matrix display required anywhere.

System Block Diagram:

The main system block diagram based on PIC32 is shown in Figure 1. In Figure 1, the interfaces required for MCU to control peripheral devices are pointed out; the modules connected by dotted arrows can be removed after each code replacement.

figure 1

Using the USB flash drive and this system can make other low-end LED dot matrix display control systems no longer rely on PCs. When multiple LED dot matrix displays are required in a short distance, the coexistence of this system and other low-end LED dot matrix display control systems can show huge cost advantages. The block diagram of the USB flash drive multiplexing control system is shown in Figure 2. In Figure 2, the interfaces required for MCU to control peripheral devices are pointed out; the modules connected by the dotted arrows indicate that they can be removed after each code change.

System function implementation principle:

The system shown in Figure 1 mainly generates LED dot matrix codes corresponding to input characters, and saves these codes to a USB flash drive and stores them in its own storage module as needed. When the code generation is completed, the display information of its own system is updated. In the process of storing codes in a USB flash drive, the address of each text code can be marked according to actual needs (the text content to be displayed in each LED display system may be different). The system shown in Figure 2 mainly obtains the text code stored in the USB flash drive in the system of Figure 1, and then updates its own display information. In the process of retrieving codes, according to the display needs of this place, the required text code is retrieved according to the address when each text is stored.

The main system shown in Figure 1 is mainly composed of six modules: MCU main control module; keyboard module; LED dot matrix display module; storage module; U disk module; LCD liquid crystal display module.

The keyboard module uses an ordinary matrix keyboard, through which each character label information is input, as well as control commands such as reading and writing U disks, deleting erroneous characters, etc. The CPU main control module imports the character label into the internal integrated LED dot matrix code generation software to generate the display code of the corresponding character, which can be saved in the storage module and the U disk at the same time. In the process of writing code to the U disk, each segment of text code can be marked with an address separately. In this way, when the U disk is reused, the operator can enter the address of a certain segment of character code to select different text information, realizing one-time writing and meeting the needs of displaying different texts in various places. Of course, the system can also read the required text code directly from the U disk for updating the display. The LCD liquid crystal display module provides a human-computer interaction interface. During each keyboard operation, the LCD is synchronized.

Display operation information (including displaying selected characters) to achieve intuitive operation.

The U disk module and the LCD liquid crystal display module can only reserve interfaces, and these two modules are plugged in when needed. After the operation is completed, the U disk and the LCD liquid crystal display can be removed for other uses.

The USB flash drive reuse control system shown in Figure 2 is also composed of six modules: MCU main control module; keyboard module; LED dot matrix display module; storage module; USB flash drive module; LED digital tube display module. The character code source provided by the system shown in Figure 1 is stored in a USB flash drive and inserted into the system shown in Figure 2. The keyboard module also uses a common matrix keyboard. The operator enters the address of any text code segment through the keyboard, selects the desired text information, and takes out the code and stores it in the storage module. After the code retrieval operation is completed, the MCU main control module takes out the new text code from the storage module to update the LED dot matrix display. The LED digital tube display module displays the address of the input text code segment in real time, allowing the operator to see his input information.

The U disk module and the LED digital tube display module can also only reserve interfaces, and these two modules are plugged in when needed. After the operation is completed, the U disk and the LED digital tube display can be removed for other uses.

System software design:

This system can be divided into two parts: the main system based on PIC32 and the USB disk multiplexing system controlled by an ordinary 8-bit microcontroller.

Figure 3 below is the software flow chart of the main system based on PIC32.

image 3

The flowchart shown in Figure 3 is a preliminary description:

After the system is powered on and initialized, the LCD display enters the initial (greeting or promotional information) interface, the LED dot matrix screen displays the previously stored text information, and the entire system waits for the operator to input command information.

Once the system receives the update text instruction, the LCD display will display the function operation interface, and the system will be ready to process the label. The operator enters the label of the corresponding character according to his needs, and the system processes the label to obtain the corresponding LED dot matrix display code and stores these codes. In the process of processing character labels, the system continuously detects whether a paragraph of text has been entered. If this paragraph of text has been entered, it will detect whether the next paragraph of text needs to be entered. The system processes each paragraph of text in the same way. In the process of storing the dot matrix code, it is stored in the U disk according to the set address of each paragraph of text by default. If it is a text code that needs to be displayed by this system, it will be stored in the U disk and the storage module of this system at the same time. After the text information is entered, the LED dot matrix display screen of this system will display the new text.

Figure 4 below is a software flow chart of a USB flash drive multiplexing system controlled by a common 8-bit microcontroller.

Figure 4

The flowchart shown in Figure 4 is a preliminary description:

After the system is powered on and initialized, the LED dot matrix screen will display the original stored content. Once the system detects the update display command, it begins to prepare to receive the address information of the text code segment stored in the U disk. After receiving the address, the LED digital tube synchronously displays this address, and the MCU module takes out the corresponding text code from the U disk and saves it in the storage module of this system. After the code is retrieved, the LED dot matrix screen begins to display the new text information.