temperature sensor

In this article we look at the TMP102 digital sensor and we will connect it up to an ESP32

Layout

esp32 and tmp102

Parts List

Code

This code example originally comes from the Arduino site with a few tweaks

[codesyntax lang=”cpp”]

#include "Wire.h"
#define TMP102_I2C_ADDRESS 72 /* This is the I2C address for our chip. This value is correct if you tie the ADD0 pin to ground. See the datasheet for some other values. */


void setup() 
{
  Wire.begin(); // start the I2C library
  Serial.begin(115200); //Start serial communication at 115200 baud
}


void loop() 
{
  getTemp102();
  delay(5000); //wait 5 seconds before printing our next set of readings. 
}

void getTemp102()
{
  byte firstbyte, secondbyte; //these are the bytes we read from the TMP102 temperature registers
  int val; /* an int is capable of storing two bytes, this is where we "chuck" the two bytes together. */ 
  float convertedtemp; /* We then need to multiply our two bytes by a scaling factor, mentioned in the datasheet. */ 
  float correctedtemp; 

  /* Reset the register pointer (by default it is ready to read temperatures)
You can alter it to a writeable register and alter some of the configuration - 
the sensor is capable of alerting you if the temperature is above or below a specified threshold. */

  Wire.beginTransmission(TMP102_I2C_ADDRESS); //Say hi to the sensor. 
  Wire.write(0x00);
  Wire.endTransmission();
  Wire.requestFrom(TMP102_I2C_ADDRESS, 2);
  Wire.endTransmission();


  firstbyte      = (Wire.read()); 
  /*read the TMP102 datasheet - here we read one byte from
   each of the temperature registers on the TMP102*/
  secondbyte     = (Wire.read()); 
  /*The first byte contains the most significant bits, and 
   the second the less significant */
    val = firstbyte;
    if ((firstbyte & 0x80) > 0) 
    {
      val |= 0x0F00;
    } 
    val <<= 4; 
 /* MSB */
    val |= (secondbyte >> 4);    
/* LSB is ORed into the second 4 bits of our byte.
Bitwise maths is a bit funky, but there's a good tutorial on the playground*/
    convertedtemp = val*0.0625;
    correctedtemp = convertedtemp - 5; 
    /* See the above note on overreading */


  Serial.print("firstbyte is ");
  Serial.print("\t");
  Serial.println(firstbyte, BIN);
  Serial.print("secondbyte is ");
  Serial.print("\t");
  Serial.println(secondbyte, BIN);
  Serial.print("Concatenated byte is ");
  Serial.print("\t");
  Serial.println(val, BIN);
  Serial.print("Converted temp is ");
  Serial.print("\t");
  Serial.println(val*0.0625);
  Serial.print("Corrected temp is ");
  Serial.print("\t");
  Serial.println(correctedtemp);
  Serial.println();
}

[/codesyntax]

Output

Open the serial monitor window and you should see something like this

firstbyte is 11100
secondbyte is 11100000
Concatenated byte is 111001110
Converted temp is 28.87
Corrected temp is 23.87

firstbyte is 11101
secondbyte is 0
Concatenated byte is 111010000
Converted temp is 29.00
Corrected temp is 24.00

firstbyte is 11011
secondbyte is 11000000
Concatenated byte is 110111100
Converted temp is 27.75
Corrected temp is 22.75

Link

http://www.ti.com/lit/gpn/tmp102

The TMP75 and TMP175 devices are digital temperature sensors ideal for NTC and PTC thermistor replacement. The devices offer a typical accuracy of ±1°C without requiring calibration or external component signal conditioning. IC temperature sensors are highly linear and do not require complex calculations or look-up tables to derive the temperature. The on-chip 12-bit ADC offers resolutions down to 0.0625°C. The devices are available in the industry standard LM75 SOIC-8 and MSOP-8 footprint.

The TMP175 and TMP75 feature SMBus, Two-Wire, and I²C interface compatibility. The TMP175 device allows up to 27 devices on one bus. The TMP75 allows up to eight 8 on one bus. The TMP175 and TMP75 both feature an SMBus Alert function.

The TMP175 and TMP75 devices are ideal for extended temperature measurement in a variety of communication, computer, consumer, environmental, industrial, and instrumentation applications.

Features

Connection

Code

[cpp]

#include <Wire.h> 

byte TempHi;              // Variable hold data high byte
byte TempLo;              // Variable hold data low byte
boolean P_N;              // Bit flag for Positive and Negative
unsigned int Decimal;     // Variable hold decimal value

void Cal_Temp();
/*******************************************************************************
                      Setup
*******************************************************************************/ 
void setup() 
{ 
  Serial.begin(9600);
  Wire.begin();             // join i2c bus (address optional for master) 
  delay(1000);
} 
 
/*******************************************************************************
                      Main Loop
*******************************************************************************/  
void loop() 
{
  const int I2C_address = 0x37;  // I2C write address 
    
  delay(100);
  Wire.beginTransmission(I2C_address);
  Wire.write(1);             // Setup configuration register
  Wire.write(0x60);          // 12-bit
  Wire.endTransmission(); 
  
  Wire.beginTransmission(I2C_address);
  Wire.write(0);             // Setup Pointer Register to 0
  Wire.endTransmission(); 
  
  while (1)
  {
    delay(1000);
    
    // Read temperature value
    Wire.requestFrom(I2C_address, 2);
    while(Wire.available())          // Checkf for data from slave
    {                                
      TempHi = Wire.read();       // Read temperature high byte
      TempLo = Wire.read();       // Read temperature low byte
    } 
    Cal_Temp ();
    
    // Display temperature
    Serial.print("The temperature is ");
    if (P_N == 0)
      Serial.print("-");
    Serial.print(TempHi,DEC);
    Serial.print(".");
    Serial.print(Decimal,DEC);
    Serial.println(" degree C");
  }  
}

void Cal_Temp()
{
  if (TempHi&0x80)          // If bit7 of the TempHi is HIGH then the temperature is negative
    P_N = 0;
  else                      // Else the temperature is positive
    P_N = 1;
  
  TempHi = TempHi & 0x7F;   // Remove sign
  TempLo = TempLo & 0xF0;   // Filter out last nibble
  TempLo = TempLo >>4;      // Shift right 4 times
  Decimal = TempLo;
  Decimal = Decimal * 625;  // Each bit = 0.0625 degree C
    
}

[/cpp]

Output

open the serial monitor and you will see something like this

The temperature is 22.8125 degree C
The temperature is 22.8125 degree C
The temperature is 23.5625 degree C
The temperature is 23.6875 degree C
The temperature is 24.3750 degree C
The temperature is 24.6250 degree C
The temperature is 25.0 degree C
The temperature is 25.2500 degree C
The temperature is 25.4375 degree C

Link

1pcs CJMCU-175 TMP175 27 Address Digital Temperature Sensor