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state machine example codes for embedded systems

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userx51

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Needed some embedded code examples in C that covers the State Machine concept. Need some examples to better grasp this topic.
 

Hello!

For a state machine, you have to list up the possible states (and combinations of states), and
list up the inputs / events that cause changes from a state to another. Here is an example (not
in C, in pseudo code with a C syntax).
Let's say you want to toggle a LED with a button press. You have 2 states, LED_ON and LED_OFF.
The button generates an event which is caught by an interrupt routine. Basically the code would
look like this:

Code C - [expand]
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enum {LED_OFF, LED_ON};
bool led_state;
 
main_program() {
    ConfigButton();
}
 
void ButtonInterrupt(void) {
    if(led_state) {
        led_state = LED_OFF;
        LEDPowerOff();
    }
    else {
       led_state = LED_ON;
        LEDPowerOn();
    }
}


That's about it, you have a two state system, and a state switching event.
NB: The main program does only configuration. This is not a mistake. In the embedded
world, everything can be event-based. If there is an event, the processor works, if not,
it sleeps. But everything can happen outside of the main program.

Dora.
 
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    shaiko

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thanks. awesome replies. If there are more sites you know of, please share.
 

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