As a new traffic guiding panel

LED light ribbon traffic guiding panel appears in recent years. On the panel

static text and route segment are shown to indicate outline and direction of roads. Traffic condition of roads

such as block

smooth and congestion are expressed by different LED colors: red

green and yellow. Control system of panel consists of an industry computer and many LED light ribbon display controllers

which all connect to RS-485 bus. The system adopts half-duplex mode and self-defined communication protocol. This paper chiefly presents design and implementation for light ribbon display controller. Each controller mainly composes of MCU

CPLD and RAM. MCU performs the task of producing display data and dealing with communication

CPLD accomplishes gray display that same color has same gray. Run length compress code is employed to ensure refreshing LED light ribbon quickly. Visiting conflict that MCU and CPLD visit the same RAM in same time can be avoided by applying interruption and software timing strategy. A method which MCU visits RAM assisting by CPLD leads to simplifying PCB wire arrangement. 16 bit constant current driver MBI5027 with function of LED open circuit error detecting makes LED detecting carry out only by software without circuit.