TMP 102 Electric IMP i2c

tmp102.nut

// Adapted from:
// http://techgurka.blogspot.com/2013/04/quick-temperature-graph-using-electric.html

class TemperatureSensor {
    i2cPort = null;
    constructor(port) {
        i2cPort = port;
        i2cPort.configure(CLOCK_SPEED_100_KHZ);
    }
    // Retrieve temperature (from local sensor) in deg F
    function getTemperature(unit) {
        i2cPort.write(0x90, "");
        i2cPort.write(0x90, "0");
 
        // Wait for conversion to finish
        imp.sleep(0.05);
        local data = i2cPort.read(0x90, "\x00", 2);
        if (data == null) {
            server.log("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;
        if (unit == 'F')
            temperature = temperature * 9 / 5 + 32;
        
        return temperature;
    }
}