Hierarchical state machine concept in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the initial state of the state machine.

Embedded C

typedef enum { STATE_IDLE, STATE_PROCESSING, STATE_ERROR } State;

State currentState = [1];

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ASTATE_IDLE

BSTATE_UNKNOWN

CSTATE_ERROR

DSTATE_PROCESSING

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a state that represents an error or processing as the initial state.

The initial state is usually set to STATE_IDLE to indicate the machine is waiting to start.

2fill in blank

medium

Complete the code to declare a nested (sub) state inside the PROCESSING state.

Embedded C

typedef enum { SUBSTATE_READ, SUBSTATE_WRITE } ProcessingSubState;

ProcessingSubState currentSubState = [1];

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ASUBSTATE_WRITE

BSUBSTATE_READ

CSUBSTATE_IDLE

DSUBSTATE_ERROR

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a substate that does not exist or is unrelated.

The substate SUBSTATE_READ is often the first step in processing data.

3fill in blank

hard

Fix the error in the transition function to correctly change the state.

Embedded C

void transitionToProcessing(State *state) {
    *state = [1];
}

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ASTATE_PROCESSING

BSTATE_ERROR

CSTATE_IDLE

DPROCESSING_STATE

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undefined state name or a wrong state.

The function should set the state to STATE_PROCESSING to indicate the machine is now processing.

4fill in blank

hard

Fill both blanks to complete the hierarchical state check.

Embedded C

if (currentState == [1]) {
    if (currentSubState == [2]) {
        // Handle read substate
    }
}

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ASTATE_PROCESSING

BSTATE_IDLE

CSUBSTATE_READ

DSUBSTATE_WRITE

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up main states and substates in the condition.

Check if the main state is STATE_PROCESSING and the substate is SUBSTATE_READ to handle reading.

5fill in blank

hard

Fill all three blanks to complete the hierarchical state machine transition.

Embedded C

switch (currentState) {
    case [1]:
        switch (currentSubState) {
            case [2]:
                currentSubState = [3];
                break;
        }
        break;
}

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ASTATE_PROCESSING

BSUBSTATE_READ

CSUBSTATE_WRITE

DSTATE_IDLE

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong state or substate names in the switch cases.

This code switches from SUBSTATE_READ to SUBSTATE_WRITE inside the STATE_PROCESSING main state.