Getting Started: Bus Stop

You should build the state machine for a bus stop signal light. It is intended for bus stops where busses only halt when there are passengers, and which are located so that it is difficult for a bus driver to see passengers when they approach. It may also be that they need to get off a larger road, but can stay on that road if there are not passengers. The solution is a signal light that passengers can activate at the buss top and which is better visible for the approaching bus.

Here are the detailed functional requirements:

• Passengers waiting at the bus stop can press a button, upon which the signal lamp switches on.
• The bus driver can switch the light off via a radio message bus.
• The light switches off 10 minutes after it was pressed, even if no bus came.
• If a passenger presses the button and the light is already on, it stays on, but the 10 minutes timer starts again with 10 minutes.

Use the following elements:

• actions lamp_on(), lamp_off(), start_timer('t', 600000)
• triggers button, bus, t
• states on, off, and an initial state

You can ignore for now that the system may be switched off, so you need no final state.

Create a State Machine, Individually

• Use some time to find a first solution each one on your own.
• Use pencil and paper.

Create a State Machine, Together

• Compare your solutions, one at a time.
• Starting again with an empty screen, whiteboard or paper, design the state machine once again, together.
• Play through this simple scenario, and correct your state machine if necessary.

Solution

• Once you are happy with your solution, have a look at my solution.
• Compare the solutions in detail. (If you find that my solution has any flaws, please discuss on MS Teams!)
• Prepare a document where you show your solution and mine side-by-side, and compare.
• Reflect about your process towards this machine.
  • What did you get right immediately?
  • What was difficult?
  • Were there misunderstandings?