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Traffic Light (Python) for Raspberry Pi

Demonstrates how to to generate Python source code from a statechart and use it on a Raspberry Pi (here: RP 3 Mod.B V1.2).

The statechart

In summary, there are two traffic lights: one for the traffic on the street, and one for pedestrians who want to cross the street. They can push a button to request their traffic light to turn green, which activates a blinking wait-light first. The street's traffic light then goes through the standard procedure, turning on the yellow light, followed by the red light, allowing the pedestrians to cross safely. After some time, the pedestrians' traffic light turns red again, and the cars are allowed to pass until the next request is made by a pedestrian.

Additionally, the traffic light can be switched off completely. This turns the yellow lights into a blinking mode, signaling that the traffic light is indeed switched off and that the street should be crossed in a careful manner.

The traffic light example is based on Python and contains an API for the Raspberry Pi that demonstrate the state machine behaviour in /model/TrafficLightCtrl.sct. This example combines generated Python code with manual Python implementations (using an API). To generate the state machine code, right-click on /model/TrafficLightCtrl.sgen and select 'Generate Code Artifacts'.

To start the application you have two options. run src/traffic/light/TrafficlightDemo.java. For this, just right-click on the project and select 'Run As > Java Application'.

The implementation of the API is based on the following circuit (created with fritzing):

The circuit

Please be aware of the following issues:

  1. The example requires Python 3.x .
  2. It's recommended to install the PyDev Plugin or something similar in your IDE first.
  3. You need the gpiozero library for _main.py_ . It is installed by default in Raspbian Jessie and Raspian x84. For further information see the documentation at readthedocs.io
  4. Before running the example, please check the hardware you are using - especially the model of your Raspberry Pi (here: Raspberry Pi 3 Model B V1.2).
  5. When you installed the example, Eclipse may show errors on the project. This is likely due to a missing configuration of the JDK. In this case select 'Properties' from the project's context menu and set the correct JDK in 'Java Build Path'. You will find further help in the 'Java development user guide' section of the Eclipse help.

Get this example​

The complete project — statechart models, sources and build files — lives in the itemis CREATE examples repository. Inside itemis CREATE for Eclipse you can import it directly with the example wizard.