Abstract: According to the structural characteristics of LED outline display control, a display controller based on STC microcontroller is designed. The system control adopts STC11/12 series single-chip microcomputer as the control processor, and the peripheral circuit uses the 485 interface to realize the master-slave remote control. Designed the ribbon data and effect data format, making full use of the limited storage space of a single piece to achieve more display effects. The sub-controller is used to complete the compatibility of the 6803, 2803 and 1809 series LED dedicated driver chips on the existing market. The LED guardrail tube display controller developed in this case has been commercialized and has good control effect.
LED guardrail tube, also known as Lid tube, is an advanced LED decorative lighting product. LEDs of red, green and blue are used as light sources, using microelectronics and digital technology, which can perform color chasing, color transition gradation, grayscale change and seven-color change, which can produce very rich color change effects. The shape of the product is formed in one time, and the tube and the base are integrated into one body, which is more waterproof and lighter in weight. It is widely used in various large-scale architectural decoration such as bars, dance halls, buildings, squares, bridges, railings, etc. Full-color tubes can realize lighting group control and display dynamic programs in a wide range of areas, suitable for large-scale theme night scenes.
In this paper, a LED outline display solution for master-slave MCU is proposed. The design scheme utilizes the FLASH ROM and RAM of the STC MCU itself. The external circuit does not need any storage circuit, and the circuit structure is simple. It can realize AC synchronous display and drive various LED guardrail tubes and point light source devices in the current LED lighting market.
1 System working principle and overall scheme design
1.1 STC microcontroller
STC series MCU is a single-machine cycle clock MCU produced by Hongjing Technology. It is a new-generation 8051 MCU with high speed, low power consumption and super anti-interference. The instruction code is fully compatible with the traditional 8051, but the speed is 8~12 times faster. Internally integrated MAX810 dedicated reset circuit for motor control and strong interference. Among them STC11FXX, STC12CXX series working voltage 4.1~5.5 V, working frequency up to 35 MHz, internal 512 bytes of RAM, cost-effective. The ISP can be operated through the serial port, and the user program can be directly downloaded without a dedicated emulator and programmer, which brings convenience to the user's development, production and maintenance.
1.2 How the system works
The LED outline display is an LED display effect connected by an LED guardrail tube connected end to end or a point light source connected in series, and is mostly used for lighting the outline of a building. The main function of the display drive circuit is to receive the digital signal from the control system, illuminate the LED, and display the information on the LED display. The LED outline shows that the widely used driver circuits are designed based on general-purpose integrated circuits, such as 74HC164, CD4015, 74HC595, 68595, ULN2803, etc., mostly shift registers and Darlington drives. The circuit design is carried out by using a conventional driving IC, the principle is relatively simple, the price is cheap, and the technical openness of the product is relatively strong. The data transmission methods on the LED display screen mainly include serial and parallel. Currently, the widely used serial control technology is mainly used. In this control mode, different driving circuits and each clock in each unit of the display unit transmit only one bit of data (one bit for each color in each implementation) for each clock. In this way, there are many types of driver ICs that can be used, and fewer connections between different display units can reduce the data transmission driving components on the display unit, thereby improving the reliability of the entire system and the ease of implementation of the specific project. .
1.3 Design of the overall system plan
The system consists of two parts: the main controller and the slave controller. The main controller has LED display and function buttons, and the user selects the display effect and display speed according to the actual situation. According to the control needs, three structures as shown in Fig. 1 can be formed.
Figure 1 Schematic diagram of LED outline display control system
The structure of Figure 1(a) is a standard master-slave structure. The main controller transmits control data to the slave controllers via the 485 bus. The main controller data is received from the controller and the LED panel is driven as required. The structure of Fig. 1(b) is a simple master-slave structure. That is, when there is no master controller or no user interaction, a slave controller acts as the master controller to send data to the slave controllers. The structure of Fig. 1(c) is a parallel synchronization structure. There is no main controller in the system, and each slave controller automatically executes according to the AC signal 50 Hz frequency, and multiple slave controllers can display simultaneously.
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