为什么我在PIC24FV32KA301上使用Vbg来测量Vdd得到的结果有问题？

嗨，我试图在PIC24FV32KA301上使用Vbg来测量（估计）Vdd，并使用这个函数：然后我用这个公式来得到浮点数：但是结果很奇怪：有时我得到的结果是3072（1.36V），有时2048（2.04V）有时结果是0……实际电压为3.5V和更高。我在这里漏掉什么东西吗？谢谢，问候，Gabrijel Erman



      以下为原文

    Hi,

I am trying to measure (estimate) Vdd by using Vbg on PIC24FV32KA301 and I use this function:
UINT16 adcMeasureSingle() {
    UINT16 result;
    AD1CON1 = 0x0470;
    AD1CON2 = 0x0000;
    AD1CON3 = 0x0100;
    AD1CON5 = 0x0010;

    while (HLVDCONbits.BGVST == 0); //wait for band gap to be active.

    AD1CHS = 0x1A1A; //input to ADC set to Vbg on A and B mux

    AD1CON1bits.ADON = 1; //activate ADC

    AD1CON1bits.SAMP = 1; //start sampling
    Nop();
    Nop();
    while (!AD1CON1bits.DONE); //wait for end
    result = ADC1BUF0; //read data
    AD1CON1bits.ADON = 0; //disable ADC

    return result;
}

Then I use this formula to get float value:
vdd_in_volts=4096*1.024/result
but the results are odd: sometimes I get result as 3072 (1.36V) , sometimes 2048 (2.04V) sometimes result is 0... Actual voltage applied is 3.5V and higher. Am I missing something here? Thanks.

Regards,
Gabrijel Erman