Wolfmans Howlings

Porting xgps to Qtopia for the Freerunner

Posted by Jim Morris on Wed Aug 27 14:46:34 -0700 2008

Background

I was getting bored waiting for Trolltech to release the next version of Qtopia for the Freerunner, so I ported the xgps client from gpsd's distribution to Qtopia.

As you may know by now, Qtopia does not have X11 so none of the existing X11 based or GTK based GPS clients work. I was exploring GPSD because I wanted to to be able to get a one time position for my sunset calculator which requires your current latitude and longitude. Although GPSD is not well suited for that (thats a whole other blog entry), I did notice you can connect to it over the ethernet, so I was playing with cgps and xgps that you find in the GPSD tar file, running on my desktop, talking to gpsd running on my Freerunner.

So wanting to dust of my Qt skills (which were so ancient I barely even recognize Qt4) I decided to port xgps to Qt.

I first did a pretty straight forward port to my Desktop Qt4/X11.

I designed the form using designer, then plugged in the code taken as closely as I could from xgps. This was not 1:1 by any means as XLib and Qt are not similar ;) I ended up just taking the ideas and algorithms from the xgps program and recoding.

So that took a day or so, as I was relearning Qt as I went, I have to say the documentation for Qt is excellent, unlike another graphics library I could mention (I'm looking at you GTK).

I got the basics working, and as my GPS fix inside was not very good (works about 50/50), I found you could also point any gpsd based client at gpsd.rellim.com and always get good data from there, this is great for testing.

So I had qtgps (for want of a better name) running on my desktop, looking pretty much the same as xgps, with the satellite list the sky view and of course the basic Fix data.

Now the trick to port it to FR, so I could run this on my FR.

The UI wasn't going to fit on the FR screen so I revamped the UI in Designer, by basically dragging all the views into a tabbed frame. So the satellite list, the sky view, the position information and the movement information all had their own tab, this fits pretty well on a tiny screen.

Other than that I didn't have to do much. I had to create a new qtgps.pro file for Qtopia, as the qmake qt one is somewhat different. I had to use the skeleton main.cpp that all Qtopia apps seem to use, but the bulk of the code remains the same.

Sending signals from callbacks

I did have an interesting time trying to figure out how to emit a signal from the gps callback thread to the main window, not sure if I chose the right way to do it but it worked... I created a singleton QObject based class, and allowed it to be called statically, then that does the emit. This is used to signal the main display thread that new gps data has arrived. (Note this won't work if the singleton can be called concurrently from multiple threads, Google c++ singleton pattern to see how to do that).

// Singleton for sending signal from a callback
class ExtSig : public QObject
{
    Q_OBJECT
    public:
        static ExtSig *self();
        void send(struct gps_data_t* p, char* buf);

    signals:
        void sendit(struct gps_data_t* p, char* buf);

    private:
        ExtSig();
};

// Singleton defns for emiting a signal from a callback
ExtSig::ExtSig(){}
ExtSig *ExtSig::self()
{
    static ExtSig inst;
    return &inst;
}

void ExtSig::send(struct gps_data_t* p, char* buf)
{
    emit sendit(p, buf);
}

// in callbeck call...
// signal the GUI thread we have new gps data
    ExtSig::self()->send(p, buf);

Howto build your own applications

Ok so how can you write your own Qtopia applications? There are at least two ways, 1) use the VMPlayer based Toolchain that Trolltech provide, or 2) setup your Linux workstation to use the toolkit. 1) is easier, and just works on pretty much anything that runs VMPlayer and has a lot of memory. 2) is faster and used less memory. I chose 2) but I did play with 1).

I won't go into how to do 1) as it is pretty much straight forward, just download the iso, and install it (either from a loopback device or from a burned CD).

The second method is not so well documented (if at all) so here is what I did to make it work on a Ubuntu Hardy i686 32-bit workstation with KDE installed..

Download the toolchain and install it into /opt/toolchains, it seems it must be there otherwise it doesn't quite work.

Then download the latest qtopia snapshot and put that in a working directory and set QTOPIA_DEPOT_PATH to that directory.

Then create a build directory for the qtopia build and set the QPEDIR environment variable to that path.

In my case I have QTOPIA_DEPOT_PATH=/opt/QtopiaSDK/qtopia-opensource-src-4.3.2-snapshot-20080815 and QPEDIR=/opt/QtopiaSDK/build/qtopia-4.3.2

Now we need to build the qtopia snapshot, you can use the result to copy to /opt/Nokia/Qtopia on your FR, or not, but you need to do this to get the tools to build your own apps.

Now follow these steps to build Qtopia:-

> cd $QPEDIR
> $QTOPIA_DEPOT_PATH/configure -device ficgta01
> make
> make install

Go get some coffee or dinner :) this will take a while.....

NOTE You may need to set -prefix /opt/Nokia/Qtopia in the ./configure stage for newer versions, as Trolltech changed where Qtopia runs from.

Now you will have a full Qtopia build in $QPEDIR/image

You can use the following script to copy this to your FR, it is modified from Trolltechs update script. It will keep your settings. However you will have needed to have flashed to the 0808 version of Qtopia and kernel for this to work.

#!/bin/sh
QTOPIA_DIR=$QPEDIR/image
QTOPIA_IMAGE=qtopia.tar.gz
PHONEIP=your_fr_ip_address
# sudo ifconfig usb0 your_fr_ip_address up

tar -C $QTOPIA_DIR czvf $QTOPIA_IMAGE
cat $QTOPIA_IMAGE | ssh "root@$PHONEIP" '(set -x;rm -f /tmp/restart-qtopia;killall qpe; mkdir -p /opt/Nokia/Qtopia;rm -rf /opt/Nokia/Qtopia/*; cd /opt/Nokia/Qtopia;gunzip |tar xvf -;/etc/init.d/qpe start &)'

Whether you do that or just keep the Trolltech released image you are now ready to write your own apps. I recommend you study the Qt docs Qtopia is pretty much Qt4.3 at the moment.

As an example you can use the qtgps.tar.gz as an example app or use $QTOPIA_DEPOT_PATH/examples/application

I created a build/myapps directory, and then tar xvfz qtgps.tar.gz into that directory. Then...

> cd build/myapps/qtgps
> $QPEDIR/bin/qtopiamake
> make

This will create a qtgps excutable that you can copy to your FR and run.

A nice trick I found is to run a GUI app from the ssh into FR you can do this...

> ssh your_fr_ip
fr# . /opt/Nokia/Qtopia/qpe.env
fr# ./qtgps

The app will popup on the FR screen, you could also run it from the terminal on the FR or from the file manager on the FR.

To create a new application you can do this..

> cd build/myapps/mynewapplication
> ... edit some .cpp and .h files
> $QPEDIR/bin/qtopiamake -project
> ... edit mynewapplication.pro appropriately
> $QPEDIR/bin/qtopiamake
> make

The skeleton main.cpp should look like this...

#include "mynewapp.h"
#include <qtopiaapplication.h>

QTOPIA_ADD_APPLICATION(QTOPIA_TARGET,MyNewApp)
QTOPIA_MAIN

The rest of the files are up to you. I like to create the UI using designer...

> $QPEDIR/bin/designer mynewapp.ui

look in either example.cpp or qtgps.cpp and qtgps.h on how to initialize a designer based UI.

There are lots of example apps on the Trolltech docs site.

Running app on the workstation

If you want to run the app locally rather than on your FR, you can use $QPEDIR/bin/qvfb

You will need to build a native version of qtopia to do that, which can be done by repeating the above steps but in a new build directory do:-

> export QPEDIR=build/qtopia-native
> mkdir $QPEDIR
> cd $QPEDIR
> $QTOPIA_DEPOT_PATH/configure -device i686fb
> make
> make install

and then rebuild your app for the native machine...

> cd build/myapps/qtgps
> make clean
> $QPEDIR/bin/qtopiamake
> make

Then run the native version of your app, but you will need to do the following to make the size correct...

> export QWS_DISPLAY=QVFb:mmWidth43:mmHeight58:0
> $QPEDIR/bin/qvfb -width 480 -height 640 &
> sleep 2
> ./qtgps -qws gpsd.rellim.com

This will run qtgps on the local workstation in a simulation of the FR screen (without qtopia), using gps data from gpsd.rellim.com.

Packaging

UPDATED I figured out how to install.

This document explains how to install a package so it shows up in the applications list, here is how I actually did it.

I created a directory called feed in my work directory, and set the path to $HTTPDIR. Then I ran a simple web server (I used boa but any will do), that points to $HTTPDIR to serve files.

Then I built the qpk package...

> cd $WORKDIR/qtgps
> make packages
> $QPEDIR/bin/mkPackages $HTTPDIR

Then make sure the web server is running, on the FR goto the Software Packages App, add the following server to the server lists http://192.168.0.200:8000, this presumes you are connected via USB and you ran the webserver at port 8000. Then click download, and you should see qtgps in the list, select it for install, and it will get installed. From then on you can replace the qtgps binary it installs with any new builds. It will be under /home/root/packages/somelongrandomstring/bin/qtgps

If you are using the vmplayer version of the SDK, then you can simply do this...

> sdk -b
> sdk -p
> sdk -i

The package for this is available here, (Right click to download). (Remember to generate the packages.list file using mkPackages). Setup a local web server and install as explained above.

A simple ruby script like this could also be used as a web server:-

--------- webserver.rb ---------
#!/usr/local/bin/ruby
require 'webrick'
include WEBrick

s = HTTPServer.new(
  :Port            => 8000,
  :DocumentRoot    => Dir::pwd
)

trap("INT"){ s.shutdown }
s.start
--------------------------------

> ruby webserver.rb

Then point your feed to http://192.168.0.200:8000/feed if using USB networking and the .qpk file is in the feed directory.

Where to get the source

The source code to this project is now on github http://github.com/wolfmanjm/qtopiagps/tree/master

Installing required libraries for the toolchain

UPDATE I forgot to mention how I got the libgps stuff into the toolchain. I found a hack, first I built gpsd-dev using mokomakefile then I did this...

dpkg-deb -X build/tmp/deploy/glibc/ipk/armv4t/gpsd-dev_2.34-r9_armv4t.ipk  /opt/QtopiaSDK/opt/toolchains/arm920t-eabi/arm-angstrom-linux-gnueabi

This worked for this case and setup the .so links correctly. You could also copy the libgps.so from your FR.

Another user (Radek Barton) did it this way, but I haven't tested this...

1. Download lastest gpsd source code at http://download.berlios.de/gpsd/gpsd-2.37.tar.gz and unpack it somewhere.
2. Add line #include <linux/limits.h> to gpsd.h-head file.
3. Modify line 15 of gps.h file from <limits.h> to <linux/limits.h>
4. configure with command: PATH=/opt/toolchains/arm920t-eabi/bin:$PATH ./configure --host=arm-angstrom-linux-gnueabi
5. Then make, make install, etc.

For those that cannot do that, then download this tar file to /pathtodownload/...

and...

> cd /
> tar xzvf /pathtodownload/libgps.tar.gz

This presumes that your Qtopia toolchain is in /opt/toolchains

Also note that the following packages need to be installed on the FR libgps16, gps-utils and gpsd.