Sleep modes overview in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enter the CPU into idle sleep mode.

Embedded C

void enter_sleep_mode() {
    __asm__("[1]");
}

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Asleep

Bhalt

Cnop

Dwfi

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'nop' which does nothing but does not sleep.

Using 'halt' which may stop the CPU but is not standard for idle sleep.

The wfi instruction puts the CPU into idle sleep mode, waiting for an interrupt.

2fill in blank

medium

Complete the code to enable deep sleep mode by setting the SLEEPDEEP bit.

Embedded C

void enable_deep_sleep() {
    SCB->SCR |= [1];
}

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ASCB_SCR_SLEEPDEEP_Msk

BSCB_SCR_SLEEPONEXIT_Msk

CSCB_SCR_SEVONPEND_Msk

DSCB_SCR_SLEEP_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong bit mask like SLEEPONEXIT which controls sleep on ISR exit.

Using a non-existent mask like SLEEP_Msk.

Setting the SLEEPDEEP bit in the System Control Block's SCR register enables deep sleep mode.

3fill in blank

hard

Fix the error in the code to correctly clear the SLEEPDEEP bit to exit deep sleep mode.

Embedded C

void disable_deep_sleep() {
    SCB->SCR &= ~[1];
}

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ASCB_SCR_SLEEP_Msk

BSCB_SCR_SLEEPDEEP_Msk

CSCB_SCR_SEVONPEND_Msk

DSCB_SCR_SLEEPONEXIT_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Clearing the wrong bit like SLEEPONEXIT.

Using the bit mask without negation.

To exit deep sleep mode, clear the SLEEPDEEP bit by ANDing with its negation.

4fill in blank

hard

Fill both blanks to create a dictionary mapping sleep mode names to their descriptions.

Embedded C

const char* sleep_modes[] = {"Idle", "[1]", "[2]"};

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AStandby

BHibernate

CSleep

DDeep

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Sleep' which is generic and not a specific mode.

Using 'Deep' alone without proper context.

The common sleep modes after Idle are Standby and Hibernate.

5fill in blank

hard

Fill all three blanks to complete the function that sets the sleep mode and enters sleep.

Embedded C

void set_sleep_mode_and_enter(int mode) {
    switch(mode) {
        case 0:
            SCB->SCR &= ~[1];
            break;
        case 1:
            SCB->SCR |= [2];
            break;
        default:
            return;
    }
    __asm__("[3]");
}

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ASCB_SCR_SLEEPDEEP_Msk

BSCB_SCR_SLEEPONEXIT_Msk

Cwfi

Dnop

Attempts:

3 left

💡 Hint

Common Mistakes

Using different bit masks for clearing and setting.

Using 'nop' instead of 'wfi' to enter sleep.

Clearing or setting SLEEPDEEP bit controls sleep depth, and wfi enters sleep mode.