TFT LCD in GPS navigator application
With the development of China's automobile industry and car users more autonomous vehicles in real-time navigation technology is receiving increasing attention, and wider application of GPS vehicle navigation system to receive satellite signals through, coupled with the electronic map data to masters of our own position in due course and destination of an embedded product, the model of autonomous navigation not collect any user fees, users can choose their own need to have access to map data.
display System GPS navigator module is an important module, the TFT color liquid crystal displays more realistic, more smooth and delicate, more layering, but also small size, light weight, etc., the design uses samsung's screen LTV350QV-F05TFTLCD. The system block diagram shown in Figure 1.
Second, XSCALPXA255 the LCD control interface processor
PXA255 processor is Intel-based company launched a nuclear XSCAL (ARM instruction set compatible) processor, which integrated LCD controller supports DSTN and TFTLCD. The LCD controller interface signals are:
L_DD [15:0]: the color data signals.
L_PCLK: pixel clock signal for the color LCD display data into the shift register, in the active mode, as the clock for points hopping.
L_LCLK: line signal for synchronization.
L_FCLK: for frame synchronization signal.
L_BIAS: color in the transmission of data at the same time, enable signal (OE) effectively in order to receive data to inform the LCD screen.
Third, LTV350QV-F05TFTLCD screen
Used in the design of Samsung's LTV350QV-F053.5-inch TFTLCD screen, this screen there are two operating modes, DE All SYNC mode model, TFTLCT screen initialization sequence and power through the simulation to configure the I2C bus. The display resolution of the largest 320 × 240, supports up to 24-bit color signal, the data interface for the RGB signal which red (R) 8, and blue (B) 8, and green (G) 8 bit.
Fourth, bias circuits and circuit VCOM
LTV350QV-F05 module has two bias voltage VGL (-10V) and the VGH (18V), and all the way analog power AVDD (5V) and digital power all the way VDD (3V). In order to save, with gate bias circuit, diodes and capacitors constitute discrete devices, the circuit shown in Figure 2, in which the system power supply LCD_5V.
(1) VCOM circuit
VCOM signal LTV350QV-F05 generated by the COM signal superimposed to form a DC voltage. VCOM signal will affect the screen display, but we can adjust the VCOM signal through the superposition of the DC voltage to adjust the LCD screen. To save board space, VCOM signal can be used to achieve an operational amplifier. The circuit schematic diagram shown in figure 3.
2) Backlight Circuit
Backlight chips can be used MP1518 driver LTV350QV-F05LCD within the six light-emitting diodes in series to achieve the backlight display, the circuit shown in Figure 4.
V, LCD driver part
LCD controller FRAMEBUFFER applications and operating system and connected. In embedded devices, FRAMBUFFER generally open in the SDRAM in a virtual display. User program through the system calls the driver FRAMBUFFER display images up to the end, part of its LCD driver block diagram in Figure 5 below:
The WindowsCE operating system design, and need to configure the initialization function LCD screen lcd_init (). This screen can be configured through the simulation of I2C interface, the main functions used are: LCDClockHigh (), LCDDataHigh (), LCDSCHigh (), LCDCSLow (), LCDClockLow (), LCDDataLow (), SDATA_OUT (), voidLCD_Write () and so on. The above function is also to achieve the simulation of I2C Bus.
lcd_init () function in the configuration of the order as shown in Figure 6.
R01-R19 which are LTV350QV-F05 internal configuration register, between the various steps in the above by adding the appropriate delay functions in order to ensure the completion of configuration registers in the LCD screen after initialization, the application can call through the system of FRAMBUFFER to operate, so the image can be displayed properly.
Program design from the above liquid crystal display module has been successfully used in GPS car navigator, the actual use of proof: clear and natural images.
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