后來查了一下代碼，問題找到了，原因是改成大屏幕以后，LCD的象素時鐘變大，應(yīng)用官方提供的代碼就出現(xiàn)問題了。

//------------------------------------------------------------------------------
/// Configures the internal clock of the LCD controller given the master clock of
/// the system and the desired pixel clock in MHz.
/// param masterClock Master clock frequency.
/// param pixelClock Pixel clock frequency.
//------------------------------------------------------------------------------
void LCD_SetPixelClock(unsigned int masterClock, unsigned int pixelClock)
{
AT91C_BASE_LCDC->LCDC_LCDCON1 = ((masterClock / (2 * pixelClock)) - 1) << 12;
}

當(dāng)應(yīng)用大屏幕的時候，后面的表達(dá)式算出來是一個負(fù)數(shù)，所以時鐘送不出來，LCD也就驅(qū)動不起來了

修改以后：

void LCD_SetPixelClock(unsigned int masterClock, unsigned int pixelClock)
{
unsigned int value;
value = masterClock / pixelClock;

if (masterClock % pixelClock)
{
value++;
}

value = value/2;

if (!value)
AT91C_BASE_LCDC->LCDC_LCDCON1 = AT91C_LCDC_BYPASS;
else
{
value -= 1;
AT91C_BASE_LCDC->LCDC_LCDCON1 = (value << 12);
}

}
參考數(shù)據(jù)手冊LCD寄存器描述，可以清楚的明白

BYPASS描述：

0 LCD象素時鐘 是由LCD控制器時鐘 根據(jù)CLKVAL分頻得到

1 LCD象素時鐘 就是LCD控制器時鐘