4. System operationFig. 1 presents

4. System operation
Fig. 1 presents the major functional units of the system. The hardware and software of the system must cooperate with each other to display efficiently the specified image on the wheel. The speed and angle of rotated are calculated using an STM32 ARM microcontroller to ensure that the image is stably displayed. The efficient control of hardware and software depend on accurate knowledge of the operational flow of the system.
4.1. System operation slow
Fig. 2 presents the operational slow of the image display system. The LED lighting strip executes the image display processes. The proposed system initializes all of the hardware devices and software programs when the system is booted. The two control modes of this system are the manual control mode and the remote control mode. The manual control can be set using the external button on the main control board. Another remote control is executed by a mobile APP that is installed on a mobile phone, over a Wi-Fi connection. The application program can establish a connection between the mobile phone and the main control board. When the main board receives packets from the mobile APP it determines which image will be generated by the LED lighting strip.
These two control modes select the corresponding image patterns that are stored in the memory of the STM32 microcontroller. An interrupt delay ensures that the imaged patterns are transmitted at the correct time from the main control board to the LED lighting module. The interrupt delay changes with the rate of rotation of the wheel. The interrupt delay is shortened as the rate of rotation increases to ensure that the displayed image is as specified. Therefore, the rate of rotation in all instances dominates the interrupt delay to display an image.
4.2. Hardware interface
Several hardware components for this system are developed. They include the main control board and three LED lighting strips. Three LED lighting strips perform the LED imaging function on the wheel; pairs of boards are separated by an angle of 120 degrees. The two kinds of major circuit board that perform the imaging function are described as follows.
(a) Main control board Fig. 3 presents the main control board. The board receives control commands from the remote application program and executes the imaging algorithm. before transmitting the control signals to the LED lighting strips. The main control