Idle mode behavior in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enter idle mode using the correct instruction.

Embedded C

void enter_idle_mode() {
    __[1]();
}

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

AWFI

BNOP

CWFE

DSVC

Attempts:

3 left

💡 Hint

Common Mistakes

Using NOP does not enter idle mode; it just does nothing for one cycle.

Using SVC triggers a supervisor call, not idle mode.

WFE waits for an event, which is different from waiting for an interrupt.

The WFI instruction puts the processor into idle mode, waiting for an interrupt.

2fill in blank

medium

Complete the code to enable the idle mode by setting the correct bit in the power control register.

Embedded C

POWER_CTRL_REG |= (1 << [1]);

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A3

B0

C2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting bit 0 might enable a different power mode.

Bits 2 and 3 are usually for other power states.

Bit 1 in the power control register enables idle mode.

3fill in blank

hard

Fix the error in the code that attempts to enter idle mode but uses the wrong instruction.

Embedded C

void idle_mode() {
    __[1]();
}

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

AWFI

BWFE

CNOP

DSVC

Attempts:

3 left

💡 Hint

Common Mistakes

Using NOP does not enter idle mode.

Using WFE waits for an event, not an interrupt.

SVC triggers a supervisor call.

The correct instruction to enter idle mode is WFI, not NOP or others.

4fill in blank

hard

Fill both blanks to create a dictionary that maps power modes to their bit positions.

Embedded C

const int power_modes_bits[] = { [1], [2] };

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A0

B1

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing bit positions for different power modes.

Bit 0 is for sleep mode, bit 1 is for idle mode.

5fill in blank

hard

Fill all three blanks to complete the function that sets the processor to idle mode and enables the correct power control bit.

Embedded C

void set_idle_mode() {
    POWER_CTRL_REG |= (1 << [1]);
    __[2]();
    while (!(STATUS_REG & (1 << [3]))) {
        ;
    }
}

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

A1

BWFI

C0

DWFE

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong bits for enabling or checking status.

Using WFE instead of WFI.

Bit 1 enables idle mode, WFI enters idle mode, and bit 0 in status register indicates idle state.