Thursday Nov 21, 2013

Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 3)

OK, sports fans. You've got your Vernier Go!Temp USB probe connected. It looks good with lsusb and you can see the /dev/ldusb0 device in your Raspberry Pi Linux shell.

So, how do you write a Java SE Embedded app to read in the turkey temp values. Well, as with most things, you search the Web and you can find how it was done previously in other non-Java inferior programming languages. ;-) Here's a great example in Python on the finninday.net site.

See: finniday.net Go!Teamp example in Python

It shows the reverse engineered byte format of the data coming over USB from the Vernier Go!Temp probe. Booyah! That's what we need to write a Java SE Embedded app. And, here it is...

/**
 *
 * @author hinkmond
 * Copyright © 2013 Oracle and/or its affiliates. All rights reserved.
 */
public class TurkeyTweeter {

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        Date date;
        FileInputStream fis = null;
        DataInputStream dis = null;
        byte   b[];
        
        double tempavg, c, f;
        int    samplecount=0, sequence=0, temp1=0, temp2=0, temp3=0;
        
        final double VERNIER_SCALING_FACTOR=126.74;
        final double VERNIER_CALIBRATION_OFFSET=5.4;

        b = new byte[8];

        // Loop to keep reading temperature
        while (true) {
            int available;

            try {
                fis = new FileInputStream("/dev/ldusb0");
                dis = new DataInputStream(fis);
            } catch (FileNotFoundException fnfe) {
                System.out.println("Cannot find temp sensor");
                fnfe.printStackTrace();
                System.exit(-1);
            }

            // Read 8 bytes from Vernier Go!Temp USB probe
            //   Format:
            //     Byte 0:   Sample Count
            //     Byte 1:   Sequence Index
            //     Byte 2-3: First temp sample
            //     Byte 4-5: Second temp sample
            //     Byte 6-7: Third temp sample
            try {
                if (dis != null) {
                    available = dis.read(b, 0, 8);
                    samplecount = b[0];
                    sequence = b[1];
                    temp1 = b[2] + b[3] * 256;
                    temp2 = b[4] + b[5] * 256;
                    temp3 = b[6] + b[7] * 256;
                }
            } catch (IOException ioe1) {
                System.out.println("Unable to get data from temp sensor");
                ioe1.printStackTrace();
            }
            
            tempavg = (temp1 + temp2 + temp3) / 3.0;
            c = tempavg / VERNIER_SCALING_FACTOR - VERNIER_CALIBRATION_OFFSET;
            
            // Convert from Fahrenheit to Celcius
            f = ((9.0/5.0) * c) + 32.0;
            
            double temperature = roundDouble(f);
            
            date = Calendar.getInstance().getTime();

            Format formatter = new SimpleDateFormat("E MMM d kk:mm:ss");
            String timedateString = formatter.format(date);

            System.out.println(timedateString+"  "+temperature);

            try {
                if (dis != null)
                    dis.close();
                if (fis != null)
                    fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ie) {
                ie.printStackTrace();
            }
        }
    }

   public static double roundDouble(double value) {
        double result = value * 100;
        result = Math.round(result);
        result = result / 100;
        return(result);
   }
}

Compile using javac, lather, rinse, repeat. And, here's the output running on the RPi (NOTE: Remember, you must run as root to access the /dev/ldusb0 device):

pi@raspberrypi ~ $ sudo java -jar TurkeyTweeter.jar
Thu Nov 21 16:42:59  71.59
Thu Nov 21 16:43:00  72.39
Thu Nov 21 16:43:01  72.39
Thu Nov 21 16:43:02  72.39
Thu Nov 21 16:43:03  72.39
Thu Nov 21 16:43:04  72.39
Thu Nov 21 16:43:05  72.39
Thu Nov 21 16:43:06  72.39
Thu Nov 21 16:43:07  72.39
Thu Nov 21 16:43:08  72.39
Thu Nov 21 16:43:09  72.39
...
As you can see, it's 72 degrees Fahrenheit in my office. The turkey won't be that temperature roasting in the oven on Thanksgiving, but we have now confirmed this part of the Turkey Tweeter works. Exciting, isn't it? :-) Next up, we will write the Java code to tweet out the values of our poor turkey as it cooks... (Yeah, poor turkey until it's inside my tummy. Then, it's yummy turkey!)

See the full series on the steps to this cool demo:
Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 1)
Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 2)
Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 3)
Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 4)
Internet of Things (IoT) Thanksgiving Special: Turkey Tweeter (Part 5)

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Hinkmond Wong's blog on making Machine to Machine (M2M) and the Incredible Internet of Things (IoT) smarter with Java Embedded Technologies

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