ISR best practices (keep it short) in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an ISR function correctly.

Embedded C

void [1](void) {
    // ISR code here
}

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Ainterrupt

BISR

CISR_Handler

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Using normal function names like 'main' or 'interrupt' without proper ISR declaration.

The ISR function should be declared with the correct name or attribute depending on the platform. Here, ISR is the correct placeholder for the interrupt service routine.

2fill in blank

medium

Complete the code to keep the ISR short by only setting a flag.

Embedded C

volatile int flag = 0;

void ISR(void) {
    [1] = 1;
}

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Aflag

Bresult

Ctemp

Dcounter

Attempts:

3 left

💡 Hint

Common Mistakes

Modifying non-volatile variables inside ISR.

In ISR best practices, keep the ISR short by setting a flag variable to signal the main program.

3fill in blank

hard

Fix the error in the ISR by disabling nested interrupts.

Embedded C

void ISR(void) {
    [1]();
    // ISR code
}

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Aenable_nested_interrupts

Benable_interrupts

Cdisable_interrupts

Dclear_interrupt_flag

Attempts:

3 left

💡 Hint

Common Mistakes

Enabling interrupts inside ISR causing nested calls.

To avoid nested interrupts causing issues, disable interrupts at the start of the ISR.

4fill in blank

hard

Fill both blanks to safely update a shared variable in ISR and main code.

Embedded C

volatile int count = 0;

void ISR(void) {
    [1]();
    count++;
    [2]();
}

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Adisable_interrupts

Benable_interrupts

Cclear_interrupt_flag

Dreset_counter

Attempts:

3 left

💡 Hint

Common Mistakes

Not disabling interrupts leading to data corruption.

Disable interrupts before updating shared variables and enable them after to avoid race conditions.

5fill in blank

hard

Fill all three blanks to implement a flag check and clear in main loop and ISR.

Embedded C

volatile int flag = 0;

void ISR(void) {
    [1] = 1;
}

int main(void) {
    while(1) {
        if ([2] == 1) {
            // handle event
            [3] = 0;
        }
    }
}

Drag options to blanks, or click blank then click option'

Aflag

Bevent

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing logic errors.

The ISR sets the flag to 1. The main loop checks the flag and clears it after handling the event.