Published April 7, 2016 © LGPL

Particle Photon & Thermo3 Click

Connect Thermo3 click board to Particle Photon and send temperature data to cloud. Simple I2C tutorial for Particle Photon.

BeginnerProtip30 minutes1,119

Things used in this project

Hardware components

Particle Photon

MikroE Thermo 3 click

Story

Background

The purpose of this project is to provide simple directions on how to use I2C communication on Particle Photon. For I2C device Thermo 3 click is used. At the same time we are going to send data into Particl dashboard.

Preparation

Everything you need for making Photon projects is on cloud. Open https://build.particle.io and login with your account. Put Photon and Thermo 3 click in breadboard and make connections as follow :

Photon 3V3 => Thermo3 3V3
Photon GND => Thermo3 GND
Photon D0 => Thermo3 SDA
Photon D1 => Thermo3 SCK

Coding

Code is very simple, but I am going to explain important details.

void setup()
{
  Serial.begin(9600);
  Wire.begin(); 
  Serial.println("Setup");
}

Setup procedure is simple, but one detail from Particle documentation is interesting :

The data rate for the USB device Serial is ignored, as USB has its own negotiated speed. Setting speed to 9600 is safe for the USB device. Setting the port to 14400 baud will cause the Photon or Electron to go into DFU mode while 28800 will allow a YMODEM download of firmware.

I2C address for Thermo3 click is 0x48 HEX. For reading data from I2C slave, we must set register pointer. We do that with Wire.write(byte(0x00)). Temperature data is 2-bytes value.

  Wire.beginTransmission(0x48);  // transmit to device (0x48)
  Wire.write(byte(0x00));       // sends instruction byte  
  Wire.endTransmission();

Request data from I2C slave must defined how many bytes we read from I2C :

  Wire.requestFrom(0x48,2);

Finally, we are going to process received data :

  if(2 <= Wire.available())    // if two bytes were received
  {
    reading = Wire.read();     // receive high byte (overwrites previous reading)
    reading = reading << 8;    // shift high byte to be high 8 bits
    reading |= Wire.read();    // receive low byte as lower 8 bits
    reading = reading >> 4;    // shift right 4 bits
    temp = reading * 0.0625;
    Serial.println(temp);   // print the reading
    Particle.publish("temperature", String(temp)); // send data to dashboard
  }

We are sending data to Serial port and with any serial terminal (Putty) we can track temperature. But it is amazing how is simple sending data to Particle dashboard. Only one line of code is required Particle.publish(event name,data)! Open URL https://dashboard.particle.io/ and login with your credentials. You will get screen :

That's it... Fast and simple.

Thermo3.ino

// 
// Mikroelektronika Thermo 3 click - DEMO
// Particle Photon
// 


void setup()
{
  Serial.begin(9600); // do not use other bitrate for Particle Photon
  Wire.begin(); 

}

int reading = 0;
float temp;
int state = LOW;

void loop()
{

  Wire.beginTransmission(0x48);  // transmit to device (0x48)
  Wire.write(byte(0x00));       // sends instruction byte  
  Wire.endTransmission();      // stop transmitting

  delay(100);
  
  Wire.requestFrom(0x48,2);
  if(2 <= Wire.available())    // if two bytes were received
  {
    reading = Wire.read();     // receive high byte (overwrites previous reading)
    reading = reading << 8;    // shift high byte to be high 8 bits
    reading |= Wire.read();    // receive low byte as lower 8 bits
    reading = reading >> 4;    // shift right 4 bits
    temp = reading * 0.0625;
    Serial.println(temp);   // print the reading
    Particle.publish("temperature", String(temp)); // send data to dashboard
  }  

  delay(5000);
}