TMP102 on Sparkfun ESP8266 Thing

Dec 01, 2015

When sparkfun made the "Thing" boards, they left the following footprints empty:

  • ATECC108A – A “full turnkey Elliptic Curve Digital Signature Algorithm (ECDSA) engine”, which can be used for unique serial numbers, hashing, key storage, or random numbers. A great start to securing your IoT project!
  • TMP102 Temperature Sensor – A simple, 12-bit, digital temperature sensor.
  • TSL2561 Light Sensor – A nifty luminosity/light sensor.
  • Plus a few footprints for decoupling capacitors.

I've been hooking up DHT11/22 to arduino uno to 433Mhz to another arduino to openhab, all over my house. What if I just used the TMP101 on a Thing, to send direct to openhab over arduino.

So here we go. a strip of 5 TMP102s acquired from RSComponents for sub $5. Soldered on to Things.

tmp102 on Things

Check out how tiny these things are (NZ postage stamp added for comparison purposes)

tmp102 is here arrow

I used the Wire library and this example code to get a reading from the sensor.

//////////////////////////////////////////////////////////////////
//©2011 bildr
//Released under the MIT License - Please reuse change and share
//Simple code for the TMP102, simply prints temperature via serial
//////////////////////////////////////////////////////////////////

#include <Wire.h>
int tmp102Address = 0x48;

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

void loop(){

  float temp = getTemperature();
  Serial.print("Temperature: ");
  Serial.println(temp);

  delay(200); //just here to slow down the output. You can remove this
}

float getTemperature(){
  Wire.requestFrom(tmp102Address,2); 

  byte MSB = Wire.read();
  byte LSB = Wire.read();

  //it's a 12bit int, using two's compliment for negative
  int TemperatureSum = ((MSB << 8) | LSB) >> 4; 

  float celsius = TemperatureSum*0.0625;
  return celsius;
}

The ambient temperature in the room was 24C (YAY SUMMER!). The reading on the board was 26C.

This is less than ideal, because i want the room temp, not the board temp.

So, conclusion: That was fun, educational, but not greatly useful - and i'll get better data from a DHT22 that's separated physically from the board slightly.

Brenda Wallace

Brenda does many things. Lately it's mostly typing softwares, and soldering gadgets.

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