performance - PIC 16f1827 ADC 转换太慢 XC8

Question

我关注了this Tutorial并更改了我的微 Controller 16f1827 的代码。我还改变了代码的功能。如果 ADC 值超过最大值的一半，则 LED 应亮起。 ADC 值，如果低于一半则关闭 LED。

// CONFIG
#pragma config FOSC = HS      // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF     // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF    // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = OFF    // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = OFF      // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF      // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF      // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF       // Flash Program Memory Code Protection bit (Code protection off)

#include <xc.h>
#include <pic16f1827.h>

#define _XTAL_FREQ 8000000

void ADC_Init()
{
  ADCON0 = 0x81;               //Turn ON ADC and Clock Selection
  ADCON1 = 0x00;               //All pins as Analog Input and setting Reference Voltages
}

unsigned int ADC_Read(unsigned char channel)
{
  if(channel > 7)              //Channel range is 0 ~ 7
    return 0;

  ADCON0 &= 0xC5;              //Clearing channel selection bits
  ADCON0 |= channel<<3;        //Setting channel selection bits
  __delay_ms(2);               //Acquisition time to charge hold capacitor
  GO_nDONE = 1;                //Initializes A/D conversion
  while(GO_nDONE);             //Waiting for conversion to complete
  return ((ADRESH<<8)+ADRESL); //Return result
}

void main()
{
  unsigned int a;
  TRISA = 0xFF;                 //Analog pins as Input
  TRISB = 0x00;                 //Port B as Output
  //TRISC = 0x00;                 //Port C as Output
  ADC_Init();                   //Initialize ADC

  do
  {
    a = ADC_Read(0);            //Read Analog Channel 0
    //PORTB = a;                  //Write Lower bits to PORTB
    //PORTC = a>>8;               //Write Higher 2 bits to PORTC


if(a > 512){
PORTBbits.RB7 = 1;
}else{
PORTBbits.RB7 = 0;
}


    __delay_ms(100);            //Delay
  }while(1);                    //Infinite Loop
}

代码在 XC8 中编译没有错误。问题是 PIC 检测 ADC 变化的速度太慢。如果我将输入引脚连接到正引用值，它会在大约 2 秒的延迟后打开 LED。当我将 ADC 输入更改为 0v 时，也会发生同样的情况。所有变化的检测速度都非常慢。为什么 ADC 工作这么慢？

Answer 1

您链接到的教程使用带有 8MHz 晶体振荡器的 PIC16F877A，而您似乎尝试使用带有内部振荡器的 PIC16F1827，而不是外部振荡器。像您所做的那样仅更改 PIC 头文件是不够的。您还必须设置所需的振荡器模式，并注意两个部分之间不同的任何其他配置选项。我不确定，但我认为16F1827的默认内部振荡器频率是1MHz，而不是8MHz。这可能在某种程度上解释您遇到的问题。

顺便说一句:不要试图伪造你的代码。确保正确配置微 Controller ，否则它们迟早会咬你的屁股。