Danny Tsang » Java

JavaME With Bluetooth GPS

Danny — Mon, 07 Mar 2011 22:44:41 +0000

Introduction

I have been getting my hands dirty with the Java Mobile Edition (JavaME) platform and I have had my ups and downs with it. It is the first time I have made a mobile Java application but I have done Java for over 4 years.

My first project was to create an application which would “talk” to a bluetooth GPS device. This would give me experience with bluetooth as well as GPS technology and it did!

The Platform Background

J2ME was based on the Java language which has been cut down for the mobile platform. To do this they have removed a lot of the packages found in Java. The base version of Java it uses is 1.4 which is pretty old now considering Java Standard Edition (JavaSE) is on 1.6. All Java enabled devices using the JavaME platform has the base packages set by the Java committee which consists of some JavaSE packages and some JavaME specific packages. Over time new optional standard package specifications have been made and vendors can pick and choose which one they want to implement into their device. All of these optional standard packages are named JSR-xxx (Java Specification Requests) where “xxx” is a number. Like Java it is a specification and it can be implemented in different ways by different manufacturers.

My First JavaME Project

I was using a Motorola A1200 phone as my test phone because it was the phone I was using at the time. It’s not the most powerful phone but it does have some JSRs built in especially bluetooth (JSR-82). I wanted to use bluetooth technology in my program because it is a wireless standard in many devices and I wanted to use GPS because I didn’t want to make a program which would send and receive files.

Introduction

The JSR packages makes developing Java applications a lot easier. There was one for bluetooth (JSR-82) and GPS (JSR-179) but unfortunately the Motorola A1200 didn’t support JSR-179. It was still possible to do GPS based program but more manual work was needed to get it to work. The first thing to do was to get the bluetooth side working before I could get it to talk to the GPS. This was the hardest part.

Bluetooth

The program had to be multithreaded to handle graphical user interface (GUI) inputs and bluetooth processes like searching devices without it appearing to hang to the user. This was slightly odd to me because I mobile devices tend to only have single core processors so I didn’t know how well it would handle more than one thread. Also I wasn’t 100% comfortable with using threads because I hadn’t used them that much in my applications. In the end it turned out just fine. I had at times I had more than 2 threads (including the main thread) running.

Do bear in mind that most mobile phones at the time of writing are only single core processors with limited power to allocate processing time to each thread.

GPS

With bluetooth connected successfully I was able to get the NEMA-0183 data. It was a series of data values from the GPS device separated by commas. An example of this is:
$GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62
All data sentences start with a “$” and followed by the type of data. Each data type contains different types of data but they may overlap in some areas. e.g two types of data strings may both contain speed.

Due to the paired down Java ME there are not a lot of text manipulation methods built into the framework and therefore a lot of methods need to be re-written to handle the GPS data.

Use Glenn Baddeley’s website to help you figure out which value is what in the comma delimited string.

Glenn Baddeley – GPS – NMEA sentence information

Java 4-Ever

Danny — Sun, 04 Jul 2010 21:13:15 +0000

This was such a funny video I had to post it.

Facebook Picture Upload Crashes Or Errors On FireFox

Danny — Mon, 31 Aug 2009 10:33:03 +0000

Recently tried to upload pictures to Facebook using Firefox only to find it crashed on me the first time and errored on the second. I thought this was odd considering it uses a Java Applet which should be compatible with Sun’s Java.

Well I found that GCJ’s implementation of java caused the problem. To solve it just remove the following packages:

sudo apt-get remove gcj libgcj-common libgcj7-0

Then install sun’s version of Java

Ubuntu Forum: Facebook Image Upload Applet Doesn’t Work

GPS on Computers

Danny — Tue, 27 May 2008 19:28:50 +0000

I have been trying to get get a bluetooth GPS device hooked up to various computers from mobile phones, Asus EEE PC to a Vista desktop. I thought it would be fairly easy but boy was I wrong.

Starting out on Linux with the Asus EEE PC the idea that Linux has is a daemon called gpsd which handles the commication between the computer and GPS. The clever idea for this is so that you can have multiple programs which “asks” the daemon for GPS information so not one program hogs the device. Also once you configured the daemon, it keeps all the settings from port to NEMA specification so all of this does not have to be repeated.

Linux

The first problem I had was establishing a connection between the GPS and computer using bluetooth. Ubuntu kept on saying the device would not accept an OBEX connection. Further investigation and I had to install gnome-bluetooth and bluez-utils. Using apt-get this was easy but it still wouldn’t let me. So I did it via command line:
hcitool scan
This picked it up and I used sdptool to get the serial profile for the device which my GPS supports.
sdptool browse xx:xx:xx:xx:xx:xx
Replace the ‘xx’ with the MAC address of the bluetooth GPS device which is displayed when you use the hcitool scan command.

This was where I got stuck. The sdptool didn’t create a serial profile and I stopped there.

Mac OSX 10.5

I then went on to try and get it working with the Mac. There wasn’t a lot of native GPS software for the Mac (that was free) but using port you could install gpsd. For port to run you need to have Xcode installed because it needs a c compiler. Xcode was over 1GB to download so it slowed my progress down. I created a bond between my MacBook Pro and the bluetooth GPS and that was fine. The cool thing was it even tells you the serial port it was on. I tried using KisMac with the GPS module but it didn’t work and also used GPSylon, a java open source GPS software.

After Xcode was downloaded and installed I had fetched gpsd but got confused to how to set up and lauch the daemon on the Mac.

Windows XP/Vista

For XP i used my bootcamp partition and Vista is my normal desktop computer. It was kind of pointless setting up GPS with the desktop because I won’t be able to move it about with me but it was worth a try. I used GPSylon but had trouble with the serial port because GPSylon was designed with *nix in mind and Windows used COM ports. Later on I found I had to jus change the line:
/dev/tty
to the COM port but I have yet to try it.

Mobile Phone

The best luck I have had was on my Motorola Ming(A1200). Technically it is and it is not a computer but it worked best here. I used GPS Track which was really good. JavaME has JSR179 built into the framework specification for location based devices. I would have thought these specification should be ported to the Java SE so that it too can make available the API’s needed for any mobile stuff but they weren’t. Also JavaME isn’t as easy to code for once you are use to version 1.5 and upwards.

BlueNext BN-909GR & SirfStar III Chip

Danny — Fri, 23 May 2008 13:33:32 +0000

I have been playing around with a BlueNext BN-909GR which has the SirfStar III GPS chip. The chip and implementation by BlueNext was amazing. I was able to get a lock of up 10 satellites on a clear bright day when the receiver was placed indoors! I was going around the house and it kept a lock on at least 1 satellite 90% of the time and it switched to DGPS when it didn’t.

When it was sitting next to me on the computer about 1.5 – 2 meters away from a glass window it had 9 satellites locked. I clenched my hand around the unit and it dropped to 5 satellites. It was impressive. Usually on a cold start it took around 1 – 2 minute to get a lock but normally it will get one faster. This was without the Assisted GPS (AGPS) aid although the chip does support it. I think the chip gets a better signal than my aging TomTom Go700.

The SirfStar III uses the NEMA 0183 standard which is the format for the GPS data from the unit. It is a string containing a series of data separated by commas. Each data is in a certain order and different standard have different data and in different order. This has posed many issues with JavaME which I will discuss in another post.

I got the BlueNext BN-909GR to try and create a J2ME midlet (application) which would use a bluetooth and a GPS device.

BugLabs Bugs

Danny — Sun, 18 May 2008 01:44:53 +0000

This cool modular open source hardware is a pretty good idea but seems a bit big and expensive. It’s a good idea and the even better part is that they use the Java to programming and the Eclipse IDE works with the SDK.

I’m sure I will have to get one of these to play around with one day but at the moment it seems the production of the bug and modules are not up to capacity and getting the bug base and modules adds up to almost the same price as a mobile phone such as the Nokia N95 with all the modules built in.

BugLabs Website
BugLabs’ Youtube Videos