Becoming a State Machine Design Mastermind

Imagine a robot with an all-around bump sensor. The response to the bump sensor activating depends on the previous state of the robot. If it had been going forward, a bump will send it backwards and vice versa. This robot exhibits behavior that is easy to model as a state machine. That is, the outputs of the machine (motor drive) depend not only on the inputs (the bump sensor) but also on the current state of the machine (going forward or backward).

As state machines go, that’s not an especially complicated one. Many state machines have lots of states with complex conditions. For example, consider a phone switchboard. The reaction to a phone going off hook depends on the state of the line. If the state is ringing, picking up the phone makes a connection. If the state is idle, the phone gets a dial tone. The switchboard also has to have states for timeouts, connection failures, three way calling, and more.

If you master state machines your design and debug cycles will both move along faster. Part of this is understanding and part is knowing about the tools you can choose to use. I’ll cover both below.

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Flying Spaghetti Monster Display

FSMintegrated

[Anthony Liekens], one of our favorite hackers from Belgium, recently completed this large (and awesome!) Flying Spaghetti Monster LED display!

With so many different holidays in December, [Anthony] decided he wanted his family to celebrate a slightly less traditional deity. The body is a massive 4′ by 8′ wooden board that we think [Anthony] cut out by hand, with a total of 300 RGB LEDs driven by an Arduino. Chicken wire mesh provides support for the LEDs in the FSM’s mouth and eyes. [Anthony] built everything in his very own backyard hackerspace called the Open Garage, which is a fantastic neighborhood hackerspace (and we should know—we stayed at his place during our European Hackerspace Tour!)

[Anthony] has a bunch of videos showing off the display on his personal YouTube channel, but stick around after the break for a quick sample that features the Flying Spaghetti Monster in the front window of his home.

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