PIC16F1773的DA问题

只看该作者 · 2018-4-2 15:35

用PIC16F1773实现DA时，参考电压选择的是VDD和VSS，即5V和0V，实际出来的值在2.5V和3.78V之间。这是为什么？
DA初始化如下：
//OE1: DAC Voltage Output Enable bit
//1 = DACx voltage level is also an output on the DACxOUT1 pin
//0 = DACx voltage level is disconnected from the DACxOUT1 pin
DAC1CON0bits.OE1 = 1;

//OE2: DAC Voltage Output Enable bit
//1 = DACx voltage level is also an output on the DACxOUT2 pin
//0 = DACx voltage level is disconnected from the DACxOUT2 pin
DAC1CON0bits.OE2 = 0;

//PSS<1:0>: DAC Positive Source Select bits
//11 = Reserved. Do not use.
//10 = FVR_buffer2
//01 =VREF+ pin
//00 =VDD
DAC1CON0bits.PSS = 0b00;

//NSS<1:0>: DAC Negative Source Select bit
//1 = VREF-
//0 =VSS
DAC1CON0bits.NSS = 0b0;

DAC1CON1 = 0;
DAC1CON0bits.EN = 1; //DAC1 enable,RA2

在1毫米中断执行：
u8 temp = 255;

DAC1CON1 = temp;

DACLDbits.DAC1LD = 1;

结果：
temp=0，da输出2.5V
temp=255.da输出3.78V

为什么不是0~5V？

只看该作者 · 2018-4-2 15:51

请高手指教