Error handling in embedded projects in Arduino - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main goal of error handling in embedded projects?

The main goal is to detect and respond to problems in the system to keep it running safely and reliably.

beginner

Name two common methods to handle errors in Arduino projects.

1. Using return codes to check if a function succeeded.
2. Using flags or status variables to indicate errors.

intermediate

Why is it important to keep error handling code simple in embedded systems?

Because embedded systems have limited memory and processing power, simple error handling avoids slowing down or crashing the system.

intermediate

What role does the watchdog timer play in error handling?

A watchdog timer resets the system if it stops responding, helping recover from unexpected errors or freezes.

beginner

How can you notify a user about an error in an Arduino project?

You can use LEDs to blink error codes, send messages over serial, or display information on an LCD screen.

Which of these is NOT a typical way to handle errors in embedded projects?

A Using return codes

B Setting error flags

C Throwing exceptions like in desktop apps

D Using a watchdog timer

Embedded projects usually avoid exceptions because they need simple, predictable error handling.

What does a watchdog timer do?

A Saves data to memory

B Resets the system if it freezes

C Increases processing speed

D Detects sensor errors

The watchdog timer resets the system if it stops responding to keep it running.

Why should error handling code be simple in embedded systems?

A To save memory and processing power

B To make the code look nice

C Because errors never happen

D To confuse the user

Embedded systems have limited resources, so simple error handling helps keep the system stable.

Which method can be used to inform users about errors in Arduino projects?

A Playing music

B Increasing CPU speed

C Changing the device color

D Blinking LEDs

Blinking LEDs is a common and simple way to show error codes to users.

What is a common way to check if a function worked correctly in embedded code?

A Return a status code

B Throw an exception

C Ignore errors

D Restart the computer

Returning a status code lets the program know if the function succeeded or failed.

Explain why error handling is important in embedded projects and describe two simple ways to implement it.

Think about system safety and simple checks.

Describe how a watchdog timer helps in error handling and what happens when it triggers.

Imagine the system stops working and needs a restart.

Practice

1. What is the main purpose of error handling in embedded projects like Arduino?

easy

A. To increase the power consumption of the device

B. To make the code run faster without checks

C. To add more sensors to the project

D. To detect and manage problems to keep the project safe and reliable

Solution

1. Step 1: Understand the role of error handling

   Error handling is used to find and manage problems that may happen during the project operation.

2. Step 2: Identify the goal of error handling in embedded systems

   It helps keep the system safe and reliable by preventing crashes or unexpected behavior.

3. Final Answer:

   To detect and manage problems to keep the project safe and reliable -> Option D

4. Quick Check:

   Error handling = detect and manage problems [OK]

Hint: Error handling means catching problems early [OK]

Common Mistakes:

• Thinking error handling speeds up code
• Confusing error handling with adding features
• Ignoring safety and reliability

2. Which of the following is the correct way to check for an error after reading a sensor value in Arduino?

easy

A. if (sensorValue == -1) { handleError(); }

B. if sensorValue = -1 then handleError();

C. if (sensorValue = -1) { handleError(); }

D. if sensorValue == -1 { handleError(); }

Solution

1. Step 1: Identify correct syntax for if statement in Arduino (C++)

   The condition must be inside parentheses and use double equals (==) to compare.

2. Step 2: Check each option for syntax correctness

   if (sensorValue == -1) { handleError(); } uses correct syntax: if (sensorValue == -1) { handleError(); }

3. Final Answer:

   if (sensorValue == -1) { handleError(); } -> Option A

4. Quick Check:

   Correct if syntax uses parentheses and '==' [OK]

Hint: Use '==' inside parentheses for comparisons [OK]

Common Mistakes:

• Using single '=' instead of '==' for comparison
• Missing parentheses around condition
• Using wrong keywords like 'then'

3. What will be the output on Serial Monitor if the following Arduino code runs and sensorValue is -1?

int sensorValue = -1;
void setup() {
  Serial.begin(9600);
  if (sensorValue == -1) {
    Serial.println("Error: Sensor not found");
  } else {
    Serial.println("Sensor OK");
  }
}
void loop() {}

medium

A. Sensor OK

B. Error: Sensor not found

C. No output

D. Compilation error

Solution

1. Step 1: Check the value of sensorValue

   sensorValue is set to -1 before setup runs.

2. Step 2: Evaluate the if condition in setup()

   Since sensorValue == -1 is true, the code prints "Error: Sensor not found" to Serial.

3. Final Answer:

   Error: Sensor not found -> Option B

4. Quick Check:

   sensorValue == -1 triggers error message [OK]

Hint: Trace variable values to predict output [OK]

Common Mistakes:

• Assuming else branch runs when condition is true
• Forgetting Serial.begin() before printing
• Confusing output with compilation errors

4. Identify the error in this Arduino code snippet for error handling:

int readSensor() {
  int val = analogRead(A0);
  if (val = -1) {
    return -1;
  }
  return val;
}

medium

A. Function should return void, not int

B. Missing semicolon after return statements

C. Using '=' instead of '==' in the if condition

D. analogRead() cannot return -1

Solution

1. Step 1: Check the if condition syntax

   The code uses single '=' which assigns -1 to val instead of comparing.

2. Step 2: Understand the impact of assignment in condition

   Assignment returns the assigned value, so condition is always true (-1 is true in C++), causing wrong behavior.

3. Final Answer:

   Using '=' instead of '==' in the if condition -> Option C

4. Quick Check:

   Use '==' to compare, not '=' [OK]

Hint: Use '==' for comparison, '=' for assignment [OK]

Common Mistakes:

• Confusing '=' and '==' in conditions
• Assuming analogRead returns -1 normally
• Ignoring return type correctness

5. You want to indicate an error in your Arduino project using an LED connected to pin 13. Which code snippet correctly turns the LED on when an error occurs (errorCode != 0) and off otherwise?

hard

A. if (errorCode != 0) { digitalWrite(13, HIGH); } else { digitalWrite(13, LOW); }

B. if (errorCode = 0) { digitalWrite(13, HIGH); } else { digitalWrite(13, LOW); }

C. if (errorCode != 0) { digitalWrite(13, LOW); } else { digitalWrite(13, HIGH); }

D. digitalWrite(13, errorCode);

Solution

1. Step 1: Understand the logic for error indication

   LED should be ON (HIGH) when errorCode is not zero, OFF (LOW) otherwise.

2. Step 2: Check each option for correct logic and syntax

   if (errorCode != 0) { digitalWrite(13, HIGH); } else { digitalWrite(13, LOW); } correctly uses '!=' to check error and sets pin 13 HIGH or LOW accordingly.

3. Final Answer:

   if (errorCode != 0) { digitalWrite(13, HIGH); } else { digitalWrite(13, LOW); } -> Option A

4. Quick Check:

   Use '!=' and digitalWrite HIGH/LOW correctly [OK]

Hint: Turn LED HIGH on error, LOW otherwise [OK]

Common Mistakes:

• Using '=' instead of '!=' in condition
• Reversing HIGH and LOW states
• Passing errorCode directly to digitalWrite