Mapping analog values with map() function in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to map the analog input value to a range from 0 to 255.

Arduino

int sensorValue = analogRead(A0);
int outputValue = map(sensorValue, 0, 1023, 0, [1]);

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

A255

B1023

C500

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1023 as the output max instead of 255.

Confusing input and output ranges.

The map() function converts the sensor value from its original range (0 to 1023) to a new range (0 to 255).

2fill in blank

medium

Complete the code to map the sensor value from 0-1023 to 100-200.

Arduino

int sensorValue = analogRead(A1);
int mappedValue = map(sensorValue, 0, 1023, [1], 200);

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

A100

B0

C50

D255

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of 100 as the output minimum.

Swapping input and output ranges.

The map() function maps the input range 0-1023 to the output range 100-200.

3fill in blank

hard

Fix the error in the code to correctly map the sensor value to 0-180 degrees.

Arduino

int sensorValue = analogRead(A2);
int angle = map(sensorValue, 0, 1023, 0, [1]);

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

A90

B180

C360

D255

Attempts:

3 left

💡 Hint

Common Mistakes

Using 90 or 360 instead of 180 as the output max.

Confusing PWM range with servo angle range.

The servo motor angle typically ranges from 0 to 180 degrees, so the mapping should use 180 as the maximum output.

4fill in blank

hard

Fill both blanks to map the sensor value from 0-1023 to 50-150 and store it in mappedVal.

Arduino

int sensorValue = analogRead(A3);
int mappedVal = map(sensorValue, [1], 1023, 50, [2]);

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

A0

B255

C150

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using 255 as input start instead of 0.

Using 100 instead of 150 as output max.

The input range starts at 0 and the output range ends at 150, so blanks should be 0 and 150 respectively.

5fill in blank

hard

Fill all three blanks to map sensorVal from 0-1023 to 10-90 and assign to result.

Arduino

int sensorVal = analogRead(A4);
int result = map(sensorVal, [1], 1023, [2], [3]);

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

A0

B10

C90

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using 100 instead of 90 as output max.

Swapping output min and max values.

The input range is 0 to 1023, and the output range is 10 to 90, so blanks are 0, 10, and 90 respectively.

Practice

1. What does the map() function do in Arduino programming?

easy

A. It converts a number from one range to another range.

B. It reads analog sensor values from pins.

C. It controls the speed of a motor.

D. It stores data in the EEPROM memory.

Solution

1. Step 1: Understand the purpose of map()

   The map() function takes a number and changes it from one range to another, like converting sensor values to a different scale.

2. Step 2: Compare with other options

   Reading analog values, controlling motors, or storing data are different functions, not what map() does.

3. Final Answer:

   It converts a number from one range to another range. -> Option A

4. Quick Check:

   map() changes ranges = C [OK]

Hint: Remember: map() changes number ranges fast [OK]

Common Mistakes:

• Confusing map() with analogRead()
• Thinking map() controls hardware directly
• Assuming map() stores data permanently

2. Which of the following is the correct syntax to map a value val from range 0-1023 to 0-255?

easy

A. map(val, 0, 255, 0, 1023);

B. map(0, 1023, val, 0, 255);

C. map(val, 0, 1023, 0, 255);

D. map(val, 255, 0, 1023, 0);

Solution

1. Step 1: Recall map() function parameters

   The correct order is: map(value, fromLow, fromHigh, toLow, toHigh).

2. Step 2: Match parameters to the question

   We want to map val from 0-1023 to 0-255, so the call is map(val, 0, 1023, 0, 255);.

3. Final Answer:

   map(val, 0, 1023, 0, 255); -> Option C

4. Quick Check:

   map(value, 0-1023, 0-255) = D [OK]

Hint: Remember parameter order: value, from range, to range [OK]

Common Mistakes:

• Swapping from and to ranges
• Putting value in wrong parameter position
• Reversing range limits

3. What is the output of this Arduino code snippet?

int sensorValue = 512;
int outputValue = map(sensorValue, 0, 1023, 0, 255);
Serial.println(outputValue);

medium

A. 0

B. 255

C. 512

D. 127

Solution

1. Step 1: Understand the mapping calculation

   Mapping 512 from 0-1023 to 0-255 scales it roughly to half the output range.

2. Step 2: Calculate mapped value

   512 is about half of 1023, so output is about half of 255, which is 127.

3. Final Answer:

   127 -> Option D

4. Quick Check:

   512 maps to 127 in 0-255 range [OK]

Hint: Half input maps to half output in linear map() [OK]

Common Mistakes:

• Using input value directly as output
• Confusing output range limits
• Rounding errors ignored

4. Identify the error in this code snippet:

int sensorValue = analogRead(A0);
int outputValue = map(sensorValue, 0, 1023, 0, 255)
Serial.println(outputValue);

medium

A. Missing semicolon after map() function call.

B. Incorrect analogRead() usage.

C. map() parameters are in wrong order.

D. Serial.println() cannot print integers.

Solution

1. Step 1: Check syntax line by line

   The line with map() is missing a semicolon at the end.

2. Step 2: Verify other lines

   analogRead(A0) and Serial.println() are used correctly.

3. Final Answer:

   Missing semicolon after map() function call. -> Option A

4. Quick Check:

   Missing semicolon = A [OK]

Hint: Check every statement ends with a semicolon [OK]

Common Mistakes:

• Forgetting semicolons after function calls
• Misordering map() parameters
• Assuming Serial.println() can't print ints

5. You want to map a sensor value from 0-1023 to a motor speed range of 100-200. Which code correctly maps and constrains the output to this range?

hard

A. int speed = map(sensorValue, 100, 200, 0, 1023);

B. int speed = constrain(map(sensorValue, 0, 1023, 100, 200), 100, 200);

C. int speed = map(sensorValue, 0, 1023, 0, 255);

D. int speed = constrain(sensorValue, 100, 200);

Solution

1. Step 1: Map sensorValue to motor speed range

   Use map(sensorValue, 0, 1023, 100, 200) to convert sensor reading to speed between 100 and 200.

2. Step 2: Constrain output to avoid out-of-range values

   Wrap with constrain(..., 100, 200) to keep speed within limits.

3. Final Answer:

   int speed = constrain(map(sensorValue, 0, 1023, 100, 200), 100, 200); -> Option B

4. Quick Check:

   Map then constrain for safe range = B [OK]

Hint: Map first, then constrain to keep values safe [OK]

Common Mistakes:

• Reversing map() range parameters
• Not constraining output causing invalid speeds
• Using constrain() without mapping first