Paul René Jørgensen

I’ll post this piece of code since it could come in handy for more developers than me.

	private static HashMap decode(int[] data) {
		HashMap m = new HashMap();

		// Extract date information
		int date = data[0] << 8 | data[1];
		int year = 2000 + (date & 0x7f); // 7 bits
		int month = (date >>> 7) & 0xf; // 4 bits
		int day = (date >>> 11) & 0×1f; // 5 bits

		// Extract time information
		int millis = data[4] << 8 | data[5]; // 16 bits
		int time = data[2] << 8 | data[3];
		int minute = time & 0x3f; // 6 bits
		int hour = (time >>> 6) & 0×1f; // 5 bits
		int second = millis / 1000;
		millis = millis % 1000;

		// Construct Date object
		Calendar c = Calendar.getInstance(TimeZone.getTimeZone(”GMT+00″));
		c.set(year, month-1, day, hour, minute, second);
		c.set(Calendar.MILLISECOND, millis);
		m.put(”gpsTime”, c.getTime());

		// Extract validity
		m.put(”valid”, (time >> 31) == 1);

		// Extract latitude
		int latValue = data[6] << 24 | data [7] << 16 | data [8] << 8 | data[9];
		if((latValue>>>31) == 1) latValue = - ((~latValue) + 1);
		m.put(”latitude”, latValue * 0.0000001);

		// Extract longitude
		int lngValue = data[10] << 24 | data [11] << 16 | data [12] << 8 | data[13];
		if((lngValue>>>31) == 1) lngValue = - ((~lngValue) + 1);
		m.put(”longitude”, lngValue * 0.0000001);

		// Extract speed
		int speedValue = data[14] << 8 | data[15];
		m.put("speed", speedValue * 0.01);

		// Extract course
		int courseValue = data[16] << 8 | data[17];
		m.put("course", courseValue * 0.01);

		// Extract altitude
		int altValue = data[18] << 8 | data[19];
		m.put("altitude", altValue);

		return m;
	}

I hereby put this code into the public domain.

Presentation I held last year for my colleagues at Adresseavisen.

I just stumbled upon an article by Werner Vogels about consistency in distributed systems. It was an eye opener and I recommend everyone interested to read it.

Eventually Consistent: “This is a specific form of weak consistency; the storage system guarantees that if no new updates are made to the object, eventually all accesses will return the last updated value. If no failures occur, the maximum size of the inconsistency window can be determined based on factors such as communication delays, the load on the system, and the number of replicas involved in the replication scheme. The most popular system that implements eventual consistency is DNS (Domain Name System). Updates to a name are distributed according to a configured pattern and in combination with time-controlled caches; eventually, all clients will see the update.”

In the same reading frenzy I also read these related pages:

• http://www.readwriteweb.com/archives/is_the_relational_database_doomed.php
• http://belaban.blogspot.com/2009/01/replcache-storing-your-data-in-cloud.html
• http://commons.apache.org/sandbox/pipeline/
• http://www.jgroups.org/demos.html
• http://www.helidb.org/

Could not help but smile and donate some more to micro loans for women at Kiva.org. You should do the same!

My employer Adresseavisen (local newspaper in Norway) released a Google Maps based property transfer database I’ve written for them today.

You can visit the application here: Eiendomsdatabasen

“In 2007, Paul Rothemund gave TED a short summary of his specialty, DNA folding. Now he lays out in clear, adundant detail the immense promise of this field — to create tiny machines that assemble themselves.”

http://www.ted.com/index.php/talks/paul_rothemund_details_dna_folding.html

I just watched this presentation and thought that I should share it with you. As a software engineer this is intrieging.

• Usemon presentation is available from Slideshare
• Usemon Live demo video is available here

Tonight I upgraded one of my Sun Spots to the new beta release of the blue firmware. One of the changes were an important bugfix in the UART code of the daughter board handling the UART buffers.

Anyway, after upgrading I wrote some test code to display the NMEA data from the GPS and guess what.. It worked!

        EDemoBoard edb = EDemoBoard.getInstance();
        edb.initUART(edb.SERIAL_SPEED_4800, edb.SERIAL_DATABITS_8, edb.SERIAL_PARITY_NONE, edb.SERIAL_STOPBITS_1);
        while(true) {
            try {
                System.out.print((char) edb.readUART(1000));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

And the output (No fix. I was in my livingroom)..

Squawk VM Starting (blue-080718)...
$GPGGA,220058.000,,,,,0,00,50.0,,M,0.0,M,,0000*40
$GPGSA,A,1,,,,,,,,,,,,,50.0,50.0,50.0*05
$GPRMC,220058.000,V,,,,,,,080808,,*2A
$GPGGA,220059.000,,,,,0,00,50.0,,M,0.0,M,,0000*41
$GPGSA,A,1,,,,,,,,,,,,,50.0,50.0,50.0*05
$GPRMC,220059.000,V,,,,,,,080808,,*2B
$GPGGA,220100.000,,,,,0,00,50.0,,M,0.0,M,,0000*4C
$GPGSA,A,1,,,,,,,,,,,,,50.0,50.0,50.0*05
$GPGSV,3,1,12,03,67,195,,06,61,164,21,19,57,270,,18,48,083,17*71
$GPGSV,3,2,12,22,46,145,17,21,26,080,,08,20,318,32,15,20,030,*74
$GPGSV,3,3,12,26,17,013,,27,12,293,,07,11,282,,16,10,185,*71
$GPRMC,220100.000,V,,,,,,,080808,,*26

Sorry for not posting any progress on this for some days, but I’ve started in my new day job and have been pretty tired in the evenings. Hopefully this will change soon, but during some spare time tonight I was able to create the proper cable to be able to interface the GPS with the Sun Spot.

I just wanted you to see that tiny red light on the GPS indicating that it’s properly powered and connected to the Sun Spot. Now that I’ve prototyped all the hardware I’m ready to tackle the the real challenge, to code this bugger! That will be a lot of fun!

Just a reminder at the end. I hope to meet a lot of you guys at JavaZone, 17.-18. September in Oslo. I’ll be at the speakers dinner on the evening the 16, but hopefully we’ll get some time to grab a few beers and talk about old times during the conference..

I just wanted to let you know about todays progress. The GPS module landed in the mailbox this morning, but I forced myself not to rush and wire it up to the Spot right away. I know that this GPS module is compatible with the Spot so there was no reason to rush it.

What I was more concerned with was the enable/disable switch and the rudder pass through signal. I started out wiring up the RC receiver to the spot and wrote some lines of code to get the pulse length of a signal connected to one of the Dx pins of the Spot.

    private int getRCPulse() {
        EDemoBoard edb = EDemoBoard.getInstance();
        IInputPin pin = edb.getIOPins()[EDemoBoard.D3];
        return edb.getPulse(pin, true, 30);
    }

These few lines of code should give me the length of the pulse coming in on the D3 pin every 30 ms measured in microseconds. And guess what happened when I connected the battery? It worked!!

Next up was to prototype the rudder servo pass through. I added some more wires to the Spot connecting the servo signal cable to one of the Hx pins and made sure the servo was powered by the RC receiver.

        Servo s = new Servo(EDemoBoard.getInstance().getOutputPins()[EDemoBoard.H1]);
        while(true) {
            int l = getRCPulse();
            s.setValue(l);
            System.out.println(l);
            Utils.sleep(1);
        }

This code reads the rudder RC channel and passes the value on to the connected servo. Amazing as it sounds, but it actually works!

I now have a spot decoding the RC receiver signal and later outputting it to a connected servo, passing it through the spot as if it was not there! This is what is supposed to happen when the autopilot is disabled. When I hit the gear switch on my transmitter the autopilot logics should kick in. But that is another story..