CMPS12 Compass - How to delete the calibration profile

Help & Support Robot Parts
1

The CMPS12 is a great compass. When I am running it on an arduino, I get great, solid, continuous results. But mounted on a robot, it boots up at 358 degrees EVERY time. I have tried to delete the cal profile to see if it needs to recalibrate for the bot, but am unsuccessful. Here is the code:

void calibrate() {

Wire.beginTransmission(CMPS12_ADDRESS);
Wire.write(0xE0);
delay(25);

Wire.beginTransmission(CMPS12_ADDRESS);
Wire.write(0xE5);
delay(25);

Wire.beginTransmission(CMPS12_ADDRESS);
Wire.write(0xE2);
Wire.endTransmission();
delay(25);

}
with reset numbers from the data sheet. This is a the way the CMPS11 was calibrated, but with the CMPS12 write numbers.

Calibration register reads a “3” [fully calibrated] all the time, even after the above function is run.

The chip is mounted above the bot, but it was mounted right on the Arduino board without problems. I can’t find example code except for the one sketch by James Henderson [2014].

Does anyone have access to more info on this chip?

Thanks

2

hello,

you have forgotten the write to the command register 0x00i and close the connection after each request send
the following function works:

void CMPS12Class::CMPS12_eraseProfil()
{
Wire.beginTransmission(_address);
Wire.write(0x00);
Wire.write(0xE0);
_last_status = Wire.endTransmission();

  delay(20); //  20ms delay after each of the three bytes send
  Wire.beginTransmission(_address);  
  Wire.write(0x00);
  Wire.write(0xE5);
  _last_status = Wire.endTransmission();
   
  delay(20); //  20ms delay after each of the three bytes send
  Wire.beginTransmission(_address);  
  Wire.write(0x00);  
  Wire.write(0xE2);
  _last_status = Wire.endTransmission();  
  
  delay(20); //  20ms delay after each of the three bytes send
3

Perfect. Thank you for the info.

Additional Question: Can this be used to read the registers as well [the only way I have found to read register 30 was to read all the registers]

For example: would this work?

begin transmission
write command register
write register needed
endTransmission
delay
read register

Thanks

4

Hello

below a piece of code the reade properly the register
hope it will help you

cheers

// Read a 16-bit register low byte high and then low byte
uint16_t BH1720Class::BH1720_readReg16BitHL(uint8_t reg)
{
  uint16_t value;
  
  Wire.beginTransmission(_address);
  Wire.write(reg);
  _last_status = Wire.endTransmission();
  if (_last_status > 0) return _last_status;

  _last_nb_receive = Wire.requestFrom(_address, (uint8_t)2);
  if (_last_nb_receive != 2) {_last_status=WIRE_REQUEST_ERROR; return _last_status;}
    
  uint8_t msb = Wire.read(); // value high byte
  uint8_t lsb = Wire.read(); // value low byte

  value  = (((uint16_t)msb) << 8) | lsb;
  
  return value;
}


double BH1720Class::BH1720_getLux()
{
  uint16_t lux = BH1720_readReg16BitHL(_address);
  if (_last_status >0) return (double)_last_status;
  
  delay (120);  // The result of continuously measurement mode is updated.( 120ms.typ at H-resolution mode)
  
  return (double)lux/1.2; // H-Resolution Mode: 1lux resolution 120ms
}
5

sorry with the good piece of code :slight_smile:

// Read an 8-bit register
uint8_t CMPS12Class::CMPS12_readReg(uint8_t reg)
{
  uint8_t value=0;

  Wire.beginTransmission(_address);
  Wire.write(reg);
  _last_status = Wire.endTransmission();
  if (_last_status > 0) return _last_status;

  _last_nb_receive = Wire.requestFrom(_address, (uint8_t)1);
  if (_last_nb_receive != 1) {_last_status=WIRE_REQUEST_ERROR; return _last_status;}
  value = Wire.read();

  return value;
}