Using two MCP9808 sensors with 1 Arduino

adrian12345 · Apr 8, 2015

Hi all,

I'm currently working on a small project where I'm looking to find a temperature gradient using two temp sensors.
I got the arduino and two sensors and have wired them as necessary, but I am having trouble with the coding.
I am able to get one sensor to work and give off temperature using this code(from adafruit) but I'm unable to configure it for two sensors.
They say that I have to set two different addresses to have them both run. So say, if A2 is tied to VDD and A0 is tied to VDD, the address is 0x18 + 4 + 1 = 0x1D. How can i put that into the code to reflect so?
Thanks.
Header:

Code:

 #if ARDUINO >= 100
 #include "Arduino.h"
#else
 #include "WProgram.h"
#endif

#ifdef __AVR_ATtiny85__
 #include "TinyWireM.h"
 #define Wire TinyWireM
#else
 #include <Wire.h>
#endif

#define MCP9808_I2CADDR_DEFAULT        0x18
#define MCP9808_REG_CONFIG             0x01

#define MCP9808_REG_CONFIG_SHUTDOWN    0x0100
#define MCP9808_REG_CONFIG_CRITLOCKED  0x0080
#define MCP9808_REG_CONFIG_WINLOCKED   0x0040
#define MCP9808_REG_CONFIG_INTCLR      0x0020
#define MCP9808_REG_CONFIG_ALERTSTAT   0x0010
#define MCP9808_REG_CONFIG_ALERTCTRL   0x0008
#define MCP9808_REG_CONFIG_ALERTSEL    0x0002
#define MCP9808_REG_CONFIG_ALERTPOL    0x0002
#define MCP9808_REG_CONFIG_ALERTMODE   0x0001

#define MCP9808_REG_UPPER_TEMP         0x02
#define MCP9808_REG_LOWER_TEMP         0x03
#define MCP9808_REG_CRIT_TEMP          0x04
#define MCP9808_REG_AMBIENT_TEMP       0x05
#define MCP9808_REG_MANUF_ID           0x06
#define MCP9808_REG_DEVICE_ID          0x07

class Adafruit_MCP9808 {
 public:
  Adafruit_MCP9808();
  boolean begin(uint8_t a = MCP9808_I2CADDR_DEFAULT);  
  float readTempF( void );
  float readTempC( void );
  int shutdown_wake( uint8_t sw_ID );

  void write16(uint8_t reg, uint16_t val);
  uint16_t read16(uint8_t reg);

 private:

  uint8_t _i2caddr;
};

Actual code:

Code:

#if ARDUINO >= 100
 #include "Arduino.h"
#else
 #include "WProgram.h"
#endif

#ifdef __AVR_ATtiny85__
 #include "TinyWireM.h"
 #define Wire TinyWireM
#else
 #include <Wire.h>
#endif

#include "Adafruit_MCP9808.h"

/**************************************************************************/
/*! 
    @brief  Instantiates a new MCP9808 class
*/
/**************************************************************************/
Adafruit_MCP9808::Adafruit_MCP9808() {
}

/**************************************************************************/
/*! 
    @brief  Setups the HW
*/
/**************************************************************************/
boolean Adafruit_MCP9808::begin(uint8_t addr) {
  _i2caddr = addr;
  Wire.begin();

  if (read16(MCP9808_REG_MANUF_ID) != 0x0054) return false;
  if (read16(MCP9808_REG_DEVICE_ID) != 0x0400) return false;

  return true;
}
 
/**************************************************************************/
/*! 
    @brief  Reads the 16-bit temperature register and returns the Centigrade
            temperature as a float.

*/
/**************************************************************************/
float Adafruit_MCP9808::readTempC( void )
{
  uint16_t t = read16(MCP9808_REG_AMBIENT_TEMP);

  float temp = t & 0x0FFF;
  temp /=  16.0;
  if (t & 0x1000) temp -= 256;

  return temp;
}



//*************************************************************************
// Set Sensor to Shutdown-State or wake up (Conf_Register BIT8)
// 1= shutdown / 0= wake up
//*************************************************************************

int Adafruit_MCP9808::shutdown_wake( uint8_t sw_ID )
{
    uint16_t conf_shutdown ;
    uint16_t conf_register = read16(MCP9808_REG_CONFIG);
    if (sw_ID == 1)
    {
       conf_shutdown = conf_register | MCP9808_REG_CONFIG_SHUTDOWN ;
       write16(MCP9808_REG_CONFIG, conf_shutdown);
    }
    if (sw_ID == 0)
    {
       conf_shutdown = conf_register ^ MCP9808_REG_CONFIG_SHUTDOWN ;
       write16(MCP9808_REG_CONFIG, conf_shutdown);
    }


    return 0;
}




/**************************************************************************/
/*! 
    @brief  Low level 16 bit read and write procedures!
*/
/**************************************************************************/

void Adafruit_MCP9808::write16(uint8_t reg, uint16_t value) {
    Wire.beginTransmission(_i2caddr);
    Wire.write((uint8_t)reg);
    Wire.write(value >> 8);
    Wire.write(value & 0xFF);
    Wire.endTransmission();
}

uint16_t Adafruit_MCP9808::read16(uint8_t reg) {
  uint16_t val;

  Wire.beginTransmission(_i2caddr);
  Wire.write((uint8_t)reg);
  Wire.endTransmission();
  
  Wire.requestFrom((uint8_t)_i2caddr, (uint8_t)2);
  val = Wire.read();
  val <<= 8;
  val |= Wire.read();  
  return val;  
}

ud23 · Apr 8, 2015

Code:

#define MCP9808_I2CADDR_Sensor2       0x1D

class Adafruit_MCP9808_2 {
 public:
  Adafruit_MCP9808_2();
  boolean begin(uint8_t a = MCP9808_I2CADDR_Sensor2);  
  float readTempF( void );
  float readTempC( void );
  int shutdown_wake( uint8_t sw_ID );

  void write16(uint8_t reg, uint16_t val);
  uint16_t read16(uint8_t reg);

 private:

  uint8_t _i2caddr;
};

In actual code you need to use this other class for same all functions.

Using two MCP9808 sensors with 1 Arduino

adrian12345

Newbie level 1

ud23

Advanced Member level 3

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Using two MCP9808 sensors with 1 Arduino

adrian12345

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ud23

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