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PyMaemo/Quick start guide

Latest revision as of 21:04, 24 March 2011

[edit] Getting Started: Setting Up Python Development Environment for N900

A basic development environment for Python development for Maemo consists of:

• A source code editor
• Some way to transfer application files to the tablet
• Easily run the application (without installing it)

Alternatively, you can try other more complex development environments, briefly described at the end of this article.

This article will cover:

• Installation of necessary packages and USB connectivity setup
• Some suggestions for Python code editors
• How to transfer the application files to the N900
• How to run the application

Application packaging and final deployment will be discussed separately at a later date.

Finally, there is a screencast demonstrating the instructions from this guide, which should help clarifying some of the steps in a real setup session.

[edit] Requirements

Before continuing, make sure you have:

Tablet requirements:

• Some kind of connectivity to the tablet (e.g. WLAN or GPRS), so that you can install required packages.
• The N900 USB cable, which will be used to transfer files to the tablet.

Host requirements:

• An SSH client. For Linux, OpenSSH (through the "ssh" command) is enough. For Windows, Tera Term can be used. For Mac you can use "ssh" command in the Terminal.
• An SCP/SFTP client. For Linux, OpenSSH (through the "scp" command) is enough. The KDE/GNOME environments also have built-in support for these protocols. For Windows, you can try WinSCP or FileZilla.

For the purposes of this tutorial, you will not need Scratchbox installed. Scratchbox would only be necessary if you are unable to test your applications on the actual tablet.

[edit] Installing required packages on N900

You will need to install two applications on the tablet:

• OpenSSH Server
• rootsh

rootsh appears to have been replaced by either running sudo gainroot directly, or by running root.

OpenSSH is needed to run commands remotely on your N900. This will make testing on the device a lot easier.

Root access is needed to allow to run commands as root on the X Terminal (using sudo gainroot).

To install these applications, follow these steps:

1. Enable the extras repository.
2. Install the packages listed above.
3. The installation will ask for a new root password for SSH access. Choose a good one.
4. Wait for installation to complete.

[edit] Enabling USB networking

USB networking allows to easily and quickly transfer files to the device and connect to it using SSH.

Note that this is not the only way to transfer files to the device. If you are already setup with your N900 and your desktop on the same LAN over Wifi, you can save yourself the trouble and skip this USB networking configuration section.

To enable USB networking, follow these steps (you need to repeat them every time you reboot the device):

1. If the USB cable is plugged and in "Mass storage mode", unplug the cable and plug it again, now selecting "PC Suite Mode".
2. On N900, open "X Terminal" and run:

rootsh ifup usb0

1. Now you need to configure the host. This is dependent on which OS (or Linux distro) you use, but there are detailed instructions for various OSes and Linux distros.

From now on you can connect to the N900 using any SSH client and the following information:

Host: 192.168.2.15
Port: 22
User: root
Password: the password setup earlier

For instance, from a Linux terminal, you can connect to the tablet using this command:

ssh root@192.168.2.15

[edit] Preparing the N900 for Python Development

To enable the full power for Python development for Maemo, you must enable the "extras-devel" repository on your device. Be advised that this might be a risky operation because extras-devel contains many untested and possibly broken packages. But it also contains the latest versions of all available Python bindings for Maemo, which we are interested on.

Note that the requirement to enable the "extras-devel" repository might be removed later.

To enable extras-devel add a new catalogue to the Application Manager, as instructed in Extras-devel (did you see the big warning on that page?)

After extras-devel is enabled, you will see on Application Manager a package called "maemo-python-device-env". Installing it will also install the basic environment necessary to run most Python applications on Maemo.

[edit] Writing your code

Any good programmer oriented editor will be enough for development. If you have some development experience, you most probably already have chosen your favorite code editor and you can simply use it.

Here we list some options, both for Linux and Windows:

• gedit: the GNOME Editor has syntax highlight support for Python
• VIM and Emacs: the most popular editors, with many advanced features and versions for both Linux and Windows
• NetBeans + Python plugin: NetBeans is a multi-platform IDE, which with help of a plugin, supports development for Python
• PyGTKEditor: a syntax highlighting Python editor which runs natively on Maemo devices

Note that none of these editors will support code completion for PyMaemo modules out of box.

For testing purposes, you can try the following code (the classic "hello world" example):

import gtk
from gtk import Window, Button, Widget
if __name__ == "__main__":
    window = Window(gtk.WINDOW_TOPLEVEL)
    window.connect("destroy", gtk.main_quit)
    button = Button("Hello World")
    button.connect_object("clicked", Widget.destroy, window)
    window.add(button)
    window.show_all()
    gtk.main()

Once you have your code written, you can proceed to copying application files to the device.

[edit] Running the Python application on the device

Now that you have the N900 properly setup and the code to run, you just need to copy the application files to the device and run it.

The simplest way to copy files it to use a SFTP or SCP client. There are many free clients available for most OSes (we listed some examples on the "Requirements" section). On the Linux command line, you can use:

scp -pr my_application/ root@192.168.2.15:/root/my_application/

Replace "my_application/" with the path to the directory which contains your application files.

Finally, to run the application on the tablet, use (from a SSH terminal):

cd /root/my_application
python my_application.py

[edit] Alternative development environments

Besides the environment described on this article, there are two alternative development environments that might or might not be more appropriate for your purposes:

PluThon (Eclipse based)

PluThon is a full Python IDE for Maemo, based on Eclipse. While PluThon is easy to use and provides a complete solution, it is not necessary for basic Python development for Maemo. If you already use Eclipse for your development, PluThon might be your best option.

Official Maemo SDK (Scratchbox based)

Scratchbox is a cross-compilation toolkit used for native Maemo development. Although it can be used in Python development as well (and comes very handy if you do not have access to a real device), it has a non-trivial learning curve and is not needed for pure Python development. However, if you plan to write new Python extensions (for instance, using Cython or Python/C API directly), Scratchbox is needed to cross-compile the C code. See the Maemo SDK section on Maemo 5 developer guide for more details on it.

Note that PluThon has built-in support for transferring and running code on the device. On the other hand, the Maemo SDK has no such support (unless you use some IDE like ESbox), so you need to follow steps similar to the ones described on this guide to copy and run your code on the tablet, if you choose to use the Maemo SDK.

[edit] Advanced tips

If you want to activate USB networking automatically upon connecting the device to the computer, just create a file called /etc/event.d/usbnet on the device with the following contents:

start on G_NOKIA_READY

console output
exec ifconfig usb0 192.168.2.15 netmask 255.255.255.0 up

This way you just have to select "PC Suite mode" when plugging the device in.