内部上拉在dsPIC33FJ128GP708A上无法正常工作

您好，我的环境：DSPIC33 FJ128GP708A，MPLABX V3.51，ICD3I已经简化了我的问题代码只有几行：如果引脚没有连接到它，它应该读取“1”，因为内部上拉。调试时效果良好。但是当PIC独立运行时，它会读取“0”。PIC用3.3V供电，用我的范围（1MOHM）和我的万用表（10MOHM）测量的电压大约是2.5V。首先我想知道为什么我不测量更高的电压。第二，我想知道为什么它只有调试时才能工作。谢谢任何帮助。丹



      以下为原文

    Hello,
my environment: dsPIC33FJ128GP708A, MPLABX v3.51, ICD3

I have simplified my problem code to just a few lines:

AD1PCFGL = 0xFFFF; // All IO = Digital
TRISBbits.TRISB15 = 1; // RB15 = Input
CNPU1bits.CN12PUE = 1; // Weak Pull-Up enabled on RB15
   
while(1){
    long int h;
    for (h=0; h < 500000; h++){
        Nop();
    }
    if (0 == PORTBbits.RB15){
        UARTPutString("rnRB15 = 0rn");
    }
    else{
        UARTPutString("rnRB15 = 1rn");
    }
}

If the pin has nothing connected to it, it should read '1', because of the internal pull-up. That works fine when debugging. But when the PIC runs in standalone, it reads '0'. The PIC is powered with 3.3V. The voltage I measure with my scope (1Mohm) and with my multimeter (10Mohm) is about 2.5V.

First I wonder why I don't measure a higher voltage. Second I wonder why it works only while debugging.

Thanks for any help.
Dan