Arduino

//Analog Hall Sensor
//using an LM393 Low Power Low Offset Valtage Dual Comparator
/**********************************
 * Analog Hall Sensor    Uno3
 * A0                    A0
 * D0                    7
 * VCC                   5V
 * GND                   GND
 *********************************/
 const int ledPin = 13;//the led attach to pin13
 int sensorPin = A0; //Select the input pin for the Sensor
 int digitalPin = 7; //D0 attach to pin7

 int sensorValue = 0; //variable to store the value coming from A0
 boolean digitalValue = 0; //variable to store the value coming from pin7

 void setup()
 {
  pinMode(digitalPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
 }

 void loop()
 {
  sensorValue = analogRead(sensorPin); //read the value of A0
  digitalValue = digitalRead(digitalPin); //read the value of D0
  Serial.print("Sensor Value ");
  Serial.println(sensorValue); //A0
  Serial.print("Digital Value "); 
  Serial.println(digitalValue);

  if (digitalValue == HIGH) //if value of D0 is HIGH
  {
    digitalWrite(ledPin, LOW); //turn off the led
  }
  if (digitalValue == LOW)
  {
    digitalWrite(ledPin, HIGH); //turn on the led
  }
  delay(1000);
 }

树莓派

C

#include <stdio.h>
#include <wiringPi.h>
#include <pcf8591.h>
#define PCF  120

int main (void)
{
    int res, tmp, status;
    wiringPiSetup();
    pcf8591Setup(PCF, 0x48); //Setup pcf8591 on base pin 120, and address 0x48
    status = 0;
    
    while(1) //loop forever
    {
        res = analogRead(PCF + 0);
        printf("Current intensity of magnetic field: %d\n", res);
        if (res-133 < 5 || res-133 > -5)
                tmp = 0;
        if (res < 128) tmp = -1;
        if (res > 138) tmp = 1;
        if (tmp != status)
        {
             switch(tmp)
             {
                 case 0:
                         printf("\n****************\n");
                         printf("* Magnet: None. *\n");
                         printf("*****************\n\n");
                         break;
                 case -1:
                         printf("\n****************\n");
                         printf("* Magnet: North. *\n");
                         printf("******************\n\n");
                         break;
                 case 1:
                         printf("\n****************\n");
                         printf("* Magnet: South. *\n");
                         printf("******************\n\n");
                         break;
             }
             status = tmp;
        }
        delay(200);
    }
    return 0;
}

python

#!/usr/bin/env python
import RPi.GPIO as GPIO
import PCF8591 as ADC
import time

def setup():
    ADC.setup(0x48)

def Print(x):
    if x == 0:
        print('*************')
        print('* No Magnet *')
        print('*************')
        print('')
    if x == 1:
        print('****************')
        print('* Magnet North *')
        print('****************')
        print('')
    if x == -1:
        print('****************')
        print('* Magnet South *')
        print('****************')
        print('')

def loop():
    status = 0
    while True:
        res = ADC.read(0)
        print('Current intensity of magentic field: ', res)
        if res-133 < 5 and res-133 > -5:
            tmp = 0
        if res < 128:
            tmp = -1
        if res > 138:
            tmp = 1
        if tmp != status:
            Print(tmp)
            status = tmp
        time.sleep(0.2)

if __name__ == '__main__':
    setup()
    loop()