Zhichuan I2C Compass

Other Hardware Sensors
1

So im trying to get this baby working. My arduino sense the magnetic compass but just read out 0 degrees. It looks like my compass is very similar to the HMC6352 so i tryed different codes and playing with them but no luck.

here is the PDF to my sensor. http://www.robotshop.com/world/PDF/zhichuan-electronics-i2c-compass-manual.pdf

#include <Wire.h> 

int compassAddress = 0x42 >> 1;  // From datasheet compass address is 0x42
                                 // shift the address 1 bit right, the Wire library only needs the 7
                                 // most significant bits for the address
int reading = 0; 

void setup() 
{ 
  Wire.begin();                // join i2c bus (address optional for master) 
  Serial.begin(9600);          // start serial communication at 9600bps 
  pinMode(48, OUTPUT);
  digitalWrite(48, HIGH);
} 
  
void loop() 
{ 
  // step 1: instruct sensor to read echoes 
  Wire.beginTransmission(compassAddress);  // transmit to device
                           // the address specified in the datasheet is 66 (0x42) 
                           // but i2c adressing uses the high 7 bits so it's 33 
  Wire.send('A');          // command sensor to measure angle  
  Wire.endTransmission();  // stop transmitting 
 
  // step 2: wait for readings to happen 
  delay(1000);               // datasheet suggests at least 6000 microseconds 
  
  // step 3: request reading from sensor 
  Wire.requestFrom(compassAddress, 2);  // request 2 bytes from slave device #33 
 
  // step 4: receive reading from sensor 
  if(2 <= Wire.available())     // if two bytes were received 
  { 
    reading = Wire.receive();   // receive high byte (overwrites previous reading) 
    reading = reading << 8;     // shift high byte to be high 8 bits 
    reading += Wire.receive();  // receive low byte as lower 8 bits 
    reading /= 10;
    Serial.println(reading);    // print the reading 
  } 

  delay(2000);                   // wait for half a second 
}
2

some thoughts:

have you tried int compassAddress = 0x42; - so without the shift ?

IIRC - Wire.endTransmission(); returns a value that can be checked if transmission worked...

Change:
Wire.send('A'); // command sensor to measure angle
=>
#define COMPASS_MEASURE 0x65 // use the hex codes as stated in the PDF
Wire.send(COMPASS_MEASURE);

YOu missed to send command 0x74 or 0x76 on page 3 - start sampling

3

Im not familiar with eighter arduino or i2c. :slight_smile:

Without the shift i loose readings from sensor.

Yes the: Wire.send('A'); was one of the things that i didnt understand. I redifined but no luck yet.

Where am i supposed to put the send command 0x76?

Thanks
Nooby Karl

4

Hi Karl,

The best place would be in the setup as one only needs to send this command once I assume. Something like below

#include <Wire.h> 

#define COMPASSADDRESS  (0x42 >> 1)
#define COMPASSCONTRINUOUSMODE 0x76
#define COMPASSREAD 0x65
#define COMPASSPIN 48

void setup() 
{ 
  Wire.begin();                // join i2c bus (address optional for master) 
  Serial.begin(9600);          // start serial communication at 9600bps 
  pinMode(COMPASSPIN , OUTPUT);
  digitalWrite(COMPASSPIN , HIGH);

  // set compass to continuous reading
  Wire.beginTransmission(COMPASSADDRESS );  
  Wire.send(COMPASSCONTRINUOUSMODE );          
  Wire.endTransmission();
} 
  
void loop() 
{ 
  // step 1: instruct sensor to read echoes 
  Wire.beginTransmission(COMPASSADDRESS);  
  Wire.send(COMPASSREAD);          
  Wire.endTransmission(); 
 
  // step 2: wait for readings to happen 
  delay(1000);               // datasheet suggests at least 6000 microseconds 
  
  // step 3: request reading from sensor 
  Wire.requestFrom(COMPASSADDRESS, 2);  // request 2 bytes from slave device
  
  delay(10); 

  // step 4: receive reading from sensor 
  if (2 <= Wire.available())     // if two bytes were received 
  { 
    int reading = Wire.receive();
    reading = reading << 8 
    reading += Wire.receive();  
    Serial.println(reading);    
  } 

  delay(2000);                  
}
5

Finally getting som numbers out. But doesnt make sense because readings are just for the declination angle. Found a xls dokument stating the second mode (reading the data) should have 3 slave write addresses: 77-65 and 61.

Did my best to paste in a copy of the spreadsheet:

The first mode slave_write_address slave_command function
0X42 0X76 stop continuously update
0X42 0X70 stop cabilation
0X42 0X72 stop
0X42 0X74 stop

The second mode slave_write_address slave_command slave_read_address read_data_h read_data_l
0x42 0x77 0x43 Dh DL sotp
0x42 0x61 0x43 Dh DL sotp
0x42 0x65 0x43 Dh DL sotp

The third mode slave_write_address slave_command write_data_h write_data_l
0x42 0x60 Dh Dl stop
0x42 0x64 Dh Dl stop

Karl

6

Im still having trouble getting some sane readings out of it. Anybody got one working properly?
Im using this code.

#include "Wire.h"

int ZCCAddress = 0x42;
int slaveAddress;             
byte headingData[2];
 unsigned int headingValue;
 unsigned int heading=0;
      int declData[2];
      int deviationData[2];
 unsigned int headFin;
 byte inverted;
  
void setup()


{
  
  slaveAddress = ZCCAddress >> 1;   //arduino uses 7-bit addresses instead of the manufacturer's 8. So shift right by 1!
  Serial.begin(38400);
          Wire.begin();
          
           int a=declination();
          int b=deviation();
          void calibration();
            Serial.println("Declinazione");
      Serial.println(a);
        Serial.println("deviazione");
            Serial.println(b);
  } 



   
void loop()
{ 

  Wire.beginTransmission(slaveAddress);

 Wire.send(0x77);      //print Direction data
 delay(25);
                              
   Wire.endTransmission();


  Wire.requestFrom(slaveAddress, 2);      
  int i = 0;

 
 while(Wire.available() && i < 2) 
  {  
   headingData[i] = Wire.receive();
    i++;
   }
   
   
   if (i==2)  // All bytes received?
    {
      
headingValue=(headingData[1] | (headingData[0]<<8));

int z;
for(z=15; z>8; z--){

headFin=bitClear(headingValue,z);

}
  
  
  byte dir;
  int x=0;
  byte head1;
#include "Wire.h"

int ZCCAddress = 0x42;
int slaveAddress;             
byte headingData[2];
 unsigned int headingValue;
 unsigned int heading=0;
      int declData[2];
      int deviationData[2];
 unsigned int headFin;
  byte inverted;
  
  int declination()  {
  
  int decl;
  Wire.beginTransmission(slaveAddress);
  Wire.send(0x60);
  Wire.send(0x00);         //  these bytes represent
  Wire.send(0x02);         //  your angle of magnetic declination (depends on place)
  delay(100);
  Wire.send(0x61);
  Wire.endTransmission();

  int i=0;
  Wire.requestFrom(slaveAddress, 2); 
  while(Wire.available() && i < 2) 
{  
  declData[i] = Wire.receive();
  i++;
} 
  
  decl=declData[1] | (declData[0]<<8);

  return decl;    //printing the decl.

} 
   
  int deviation(){
  int devi; 
  Wire.beginTransmission(slaveAddress);
  Wire.send(0x64);                      
  Wire.send(0x00);        //these bytes represent
  Wire.send(0x01);        //your angle of magnetic deviation
  delay(100);
  Wire.send(0x65);
  Wire.endTransmission();
 
  int i=0;
  Wire.requestFrom(slaveAddress, 2); 
  while(Wire.available() && i < 2) 
{  
  deviationData[i] = Wire.receive();
  i++;
} 

  devi=deviationData[1] | (deviationData[0]<<8);
  return devi;   //print it out
}
  

void setup()
{
  
  slaveAddress = ZCCAddress >> 1;   //arduino uses 7-bit addresses instead of the manufacturer's 8. So shift right by 1!
  Serial.begin(9600);
          Wire.begin();
          
           int a=declination();
          int b=deviation();
          void calibration();
            Serial.println("DECLINATION");
      Serial.println(a);
        Serial.println("DEVIATION");
            Serial.println(b);
} 

void loop()
{ 

  Wire.beginTransmission(slaveAddress);

 Wire.send(0x77);      //print Direction data
 delay(25);
                              
   Wire.endTransmission();

  Wire.requestFrom(slaveAddress, 2);      
  int i = 0;
 
 while(Wire.available() && i < 2) 
{  
   headingData[i] = Wire.receive();
    i++;
}
      
   if (i==2)  // All bytes received?
{
      
headingValue=(headingData[1] | (headingData[0]<<8));

int z;
for(z=15; z>8; z--){

headFin=bitClear(headingValue,z);
  
}
    
  byte dir;
  int x=0;
  byte head1;
  head1=headingData[0]>>1;
  for(x=7; x>2; x--){
  
    dir=bitClear(head1,x);
    
}
if(dir==B00000000){
  Serial.print("N ");  
}
if(dir==B00000001){
  Serial.print("N-E ");  
}
if(dir==B00000010){
  Serial.print("E ");  
}
if(dir==B00000011){
  Serial.print("S-E ");  
}
if(dir==B00000100){
  Serial.print("S ");  
}
if(dir==B00000101){
  Serial.print("S-V ");  
}
if(dir==B00000110){
  Serial.print("V ");  
}
if(dir==B00000111){
  Serial.print("N-V ");  
} 

  Serial.print(headingValue);
  Serial.println(" Deg");
   }
   else
   Serial.print("ERROR");
   
   delay(1000);
}