The Car Audio World System Which Is Based On VisualSTATE Mechanisam And FreeRTOS

For a traditional car audio system with CD, taking into account the vibration what is brought by cars audio system when working in the uneven road,it’s needed special circuit design for the CD servo to control system vibration, high cost, complex software design and maintenance inconvenient. With more master chip which is integrated USB and SD controller, and use USB devices and SD cards to replace CD that become a trend. In consideration of this,it’s designed a state machine and Free RTOS Visual STATE system that is based on car audio system solutions, also from hardware and software design to achieve a low cost and high stability of the system.In hardware design aspects: First,Use the main controller chip which is integrated USB controller and SD controller to replace the servo control system to reduce costs;Second, for the car audio system which appeares to be unstable when loading USB disk system showed in some experimental tests, the case that is designed a reset circuit power supply, combined with software to reset the power to improve the stability of the USD disk. Third, ACC power of car audio system is provided by the car’s engine-powered systems, and the engine power system electromagnetic is easy interferenced by other factors so it may cause voltage appears to fluctuate, so the design of a hardware floating against ACC voltage detection circuit, by setting module IO power control pin for protection chip devices,improve system stability; fourth,for displaying chip and matrix keyboard via a digital strobe chips and diodes to achieve shared resources 8 IO ports isolation, rotary encoders keyboard connected through clever the resistor divider circuit, through an AD port to determine the direction of rotation than the traditional use of two IO port to achieve judgment, saving IO resources, further reducing system cost.In software design: one system using Free RTOS tasks to manage each module program, do not call any other modules directly,only by sending a message event notification task to implement calls between modules,and to improve the real-time systemto achieve the independence of each module, reducing the coupling of software, help software development and porting; on the other hand can be performed using an intuitive graphical design is based on a logical response to an event trigger mechanism in the engine of Visuasl STATE state machine tools, dynamic normative certification guarantees Stability control system logic.Finally, by a large number of experimental tests, this paper design a low-cost car audio system that has been realized in part depot production stage.