Ellectric imp TMP102 logger. Blog post: http://www.slickstreamer.info/2014/01/simpel-electric-imp-temperature-logger.html

agent.nut

local thingspeakUrl = "http://api.thingspeak.com/update";
local headers = {"Content-Type": "application/x-www-form-urlencoded",
                  "X-THINGSPEAKAPIKEY":"key"};
local field = "field1";
function httpPostToThingspeak (data) {
  local request = http.post(thingspeakUrl, headers, data);
  local response = request.sendsync();
  return response;
}


device.on("updateTemp", function(temp) {
   local response =  httpPostToThingspeak(field +"="+temp);
   server.log(response.body);
});

device.nut

/** Temperature monitor using TMP102 chip over I2C */
// Temperature Sensor Class for TMP102
class TemperatureSensor
{
    i2cPort = null;
    i2cAddress = null;
    constructor(port)
    {
        hardware.configure(I2C_12);
        i2cPort = hardware.i2c12;

        i2cPort.configure(CLOCK_SPEED_100_KHZ);
        i2cAddress = (0x48) << 1;
        server.log(format("i2cAddress=%x", i2cAddress));
        // Start continuous conversion
        i2cPort.write(i2cAddress, "");
        i2cPort.write(i2cAddress, "0");
        imp.sleep(0.05);
    }
    // Retrieve temperature (from local sensor) in deg F
    function getTemperature()
    {
        local data = i2cPort.read(i2cAddress, "\x00", 2);
        if (data == null)
        {
            server.show("Error reading TMP102");
            return null;
        }

        // Remove two's complement if negative temperature
        local degrees = data[0];
        if (degrees & 0x80)
            degrees = -((degrees - 1) ^ 0xFF);
            
        // Calculate no of steps. Each step is 0.0625 degrees centigrades
        local steps = degrees * 16 + (data[1] >> 4);
        
        local temperature = steps * 0.0625;
        
        local volt = hardware.voltage();
        return temperature;
    }
}

// Instantiate the sensor
local sensor = TemperatureSensor(I2C_12);

function getTemp()
{
    local temp = sensor.getTemperature();
    server.log(temp);
    if (temp != null)
    {
        server.log("Current temp is "+temp+" °C");
        agent.send("updateTemp", temp);
    }
    
}


imp.onidle(function() {
    getTemp();
    
   server.sleepfor(600);
});