Configuring watchdog timeout in Embedded C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the watchdog timeout to 2 seconds.

Embedded C

WDT->CONFIG = [1];

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

AWDT_CONFIG_TIMEOUT_500MS

BWDT_CONFIG_TIMEOUT_1S

CWDT_CONFIG_TIMEOUT_2S

DWDT_CONFIG_TIMEOUT_4S

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a timeout value that is too short or too long for the requirement.

Using a constant that does not exist in the watchdog configuration.

The constant WDT_CONFIG_TIMEOUT_2S sets the watchdog timer to 2 seconds timeout.

2fill in blank

medium

Complete the code to enable the watchdog timer after configuring the timeout.

Embedded C

WDT->CTRL = [1];

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

AWDT_CTRL_ENABLE

BWDT_CTRL_DISABLE

CWDT_CTRL_PAUSE

DWDT_CTRL_RESET

Attempts:

3 left

💡 Hint

Common Mistakes

Using the disable constant instead of enable.

Confusing reset with enable.

The WDT_CTRL_ENABLE constant enables the watchdog timer to start counting down.

3fill in blank

hard

Fix the error in the code to correctly reload the watchdog timer counter.

Embedded C

WDT->RELOAD = [1];

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

A0x00

BWDT_RELOAD_MAX

C0xFF

DWDT_RELOAD_VALUE

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the reload register to zero, which does not reset the timer.

Using an undefined constant.

The watchdog reload register must be set to WDT_RELOAD_VALUE to reset the timer counter properly.

4fill in blank

hard

Fill both blanks to configure the watchdog timeout and enable it.

Embedded C

WDT->CONFIG = [1];
WDT->CTRL = [2];

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

AWDT_CONFIG_TIMEOUT_1S

BWDT_CTRL_DISABLE

CWDT_CTRL_ENABLE

DWDT_CONFIG_TIMEOUT_4S

Attempts:

3 left

💡 Hint

Common Mistakes

Using disable instead of enable for the control register.

Choosing the wrong timeout constant.

Set the timeout to 1 second and enable the watchdog timer to start it.

5fill in blank

hard

Fill all three blanks to set a 4-second timeout, enable the watchdog, and reload the counter.

Embedded C

WDT->CONFIG = [1];
WDT->CTRL = [2];
WDT->RELOAD = [3];

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

AWDT_CONFIG_TIMEOUT_2S

BWDT_CTRL_ENABLE

CWDT_RELOAD_VALUE

DWDT_CONFIG_TIMEOUT_4S

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to reload the watchdog counter after enabling.

Choosing the wrong timeout duration.

Configure the watchdog for 4 seconds timeout, enable it, and reload the counter to start fresh.

Practice

1.

What is the main purpose of configuring a watchdog timer's timeout in embedded C?

easy

A. To enable debugging messages

B. To increase the CPU clock speed

C. To set how long the system waits before resetting if it hangs

D. To allocate memory for variables

Solution

1. Step 1: Understand watchdog timer role

   The watchdog timer resets the system if it stops responding.

2. Step 2: Identify timeout configuration purpose

   Timeout sets the wait time before reset triggers.

3. Final Answer:

   To set how long the system waits before resetting if it hangs -> Option C

4. Quick Check:

   Watchdog timeout = reset delay [OK]

Hint: Timeout controls reset delay after hang [OK]

Common Mistakes:

• Confusing timeout with CPU speed
• Thinking timeout allocates memory
• Assuming timeout enables debugging

2.

Which of the following is the correct syntax to set a watchdog timeout to 5000 milliseconds in embedded C?

void setup_watchdog() {
    // Set timeout here
}

easy

A. WDT_SetTimeout(5000);

B. WDT_SetTimeoutMs(5000);

C. watchdog.timeout = 5000;

D. set_watchdog(5000);

Solution

1. Step 1: Identify common watchdog API

   Many embedded C libraries use WDT_SetTimeoutMs() to set timeout in ms.

2. Step 2: Check syntax correctness

   WDT_SetTimeoutMs(5000); correctly sets 5000 ms timeout.

3. Final Answer:

   WDT_SetTimeoutMs(5000); -> Option B

4. Quick Check:

   Correct function name with ms unit [OK]

Hint: Look for function with 'TimeoutMs' for milliseconds [OK]

Common Mistakes:

• Using incorrect function names
• Assigning timeout to struct without function
• Using generic function names not in API

3.

Given the code below, what will be the watchdog timeout value after execution?

typedef struct {
    unsigned int timeout_ms;
} Watchdog;

Watchdog wdt;

void configure_watchdog(unsigned int t) {
    wdt.timeout_ms = t;
}

int main() {
    configure_watchdog(3000);
    configure_watchdog(7000);
    return wdt.timeout_ms;
}

medium

A. 7000

B. 3000

C. 0

D. Compilation error

Solution

1. Step 1: Trace function calls

   First call sets timeout_ms to 3000, second call overwrites it to 7000.

2. Step 2: Check return value

   Main returns wdt.timeout_ms, which is 7000 after second call.

3. Final Answer:

   7000 -> Option A

4. Quick Check:

   Last set timeout = 7000 [OK]

Hint: Last assignment overwrites previous timeout [OK]

Common Mistakes:

• Assuming first call value remains
• Confusing return value with function return
• Thinking timeout resets automatically

4.

Identify the error in the following watchdog timeout configuration code:

void setup_watchdog() {
    int timeout = 2000;
    WDT_SetTimeout(timeout);
    timeout = 5000;
}

medium

A. Timeout value is changed after setting watchdog, ineffective

B. WDT_SetTimeout requires unsigned int, not int

C. Missing return statement in function

D. Timeout variable should be global

Solution

1. Step 1: Analyze timeout variable usage

   Timeout is set to 2000 and passed to WDT_SetTimeout, then changed to 5000 but not applied.

2. Step 2: Understand effect of changing timeout after setting

   Changing timeout variable after setting watchdog has no effect on watchdog timeout.

3. Final Answer:

   Timeout value is changed after setting watchdog, ineffective -> Option A

4. Quick Check:

   Changing variable after call doesn't update watchdog [OK]

Hint: Set timeout once before calling watchdog function [OK]

Common Mistakes:

• Thinking variable change updates watchdog automatically
• Confusing variable type with function parameter
• Expecting return in void function

5.

You want to configure a watchdog timer that resets the system if it hangs for more than 10 seconds, but also want to avoid false resets during long processing tasks. Which approach is best?

hard

A. Set timeout to 20 seconds and never reset watchdog

B. Set timeout to 1 second to catch hangs quickly

C. Disable watchdog during long tasks

D. Set timeout to 10 seconds and reset watchdog regularly during long tasks

Solution

1. Step 1: Understand watchdog timeout role

   Timeout defines max hang time before reset; too short causes false resets.

2. Step 2: Balance timeout and reset calls

   Setting 10 seconds timeout and resetting watchdog during long tasks avoids false resets.

3. Final Answer:

   Set timeout to 10 seconds and reset watchdog regularly during long tasks -> Option D

4. Quick Check:

   Timeout + regular reset prevents false resets [OK]

Hint: Use longer timeout + reset watchdog in long tasks [OK]

Common Mistakes:

• Setting too short timeout causing resets
• Disabling watchdog risking no recovery
• Never resetting watchdog causing reset