msp430F417的LCD外置分压电阻的分压总是不对

最近在用msp430F417做个段码LCD显示的东西，屏为4mux，1/3bias，3.3V的，折腾了近半个月了，外部分压电阻的电压为屏的驱动偏置电压，结果外置电阻的分压总是不对，如0V,1.3V,1.7V,3.2V，应该为0V，1.1V，2.2V，3.3V，而且R13和R23的端口电压总有wave出现，求各位指导下，电路图和初始化程序如下

int main( void )
{
//close watchdog 
WDTCTL = WDTPW + WDTHOLD;
//system clock set
FLL_CTL0 |= XCAP14PF; // Set load capacitance for xtal 
SCFQCTL = 0x7f;
//LCD Controller register initial
LCDCTL = 0x3D; //001 S0-S15 are LCD function;11 4-mux;1 All LCD segments are enabled;unused;1 LCD timing generator and Ron are on
BTCTL = BTFRFQ0; // Set freqLCD = ACLK/64 = 512

// Set Rxx and COM pins for LCD
P5SEL = 0XFC;
//Port initial
P1DIR = 0x02; // P1.1 to output direction
P1SEL = 0x02; // P1.1 to output MCLK 
P2DIR = 0XFF;

...............

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谢谢大家。