Wire library for I2C in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the I2C communication as a master.

Arduino

Wire.[1]();

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

Astart

Bopen

Cinit

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' instead of 'begin' causes a compilation error.

Trying to use 'init' or 'open' which are not Wire library functions.

The Wire.begin() function initializes the I2C bus as a master.

2fill in blank

medium

Complete the code to send a byte of data over I2C.

Arduino

Wire.[1](0x42);

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

Awrite

Bsend

Ctransmit

Dput

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' or 'transmit' which are not valid Wire functions.

Confusing with other communication libraries.

The Wire.write() function sends data bytes to the I2C device.

3fill in blank

hard

Fix the error in the code to request 4 bytes from a device with address 0x3C.

Arduino

Wire.requestFrom([1], 4);

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

A0x30

B0xC3

C0x3C

D0x03

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong address like 0x30 or 0xC3 causes no response.

Confusing 7-bit and 8-bit addresses.

The device address must be the 7-bit I2C address, here 0x3C.

4fill in blank

hard

Fill both blanks to start transmission to address 0x50 and end it properly.

Arduino

Wire.[1](0x50);
Wire.[2]();

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

AbeginTransmission

Bstart

CendTransmission

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' or 'stop' which are not Wire library functions.

Mixing up the order of functions.

beginTransmission() starts communication with the device, and endTransmission() ends it.

5fill in blank

hard

Fill all three blanks to read bytes from a device and store them in a variable.

Arduino

int data = Wire.[1]();
while(Wire.[2]()) {
  data = Wire.[3]();
}

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

Aavailable

Cread

Dwrite

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' instead of 'read' to get data.

Confusing 'available' with 'read'.

Wire.available() checks if data is ready to read, and Wire.read() reads the data byte.

Practice

1. What is the main purpose of the Wire.begin() function in Arduino's Wire library?

easy

A. To request data from a device on the I2C bus

B. To send data to a device on the I2C bus

C. To end the I2C communication

D. To initialize the I2C bus and join the I2C network

Solution

1. Step 1: Understand the role of Wire.begin()

   The Wire.begin() function sets up the Arduino as a master or slave on the I2C bus and starts the communication.

2. Step 2: Differentiate from other Wire functions

   Functions like Wire.beginTransmission() and Wire.requestFrom() handle sending and receiving data, not initialization.

3. Final Answer:

   To initialize the I2C bus and join the I2C network -> Option D

4. Quick Check:

   Wire.begin() starts I2C communication [OK]

Hint: Wire.begin() always starts I2C communication [OK]

Common Mistakes:

• Confusing Wire.begin() with data sending functions
• Using Wire.beginTransmission() to start communication
• Thinking Wire.begin() sends or receives data

2. Which of the following is the correct syntax to start sending data to an I2C device with address 0x3C using the Wire library?

easy

A. Wire.start(0x3C);

B. Wire.beginTransmission(0x3C);

C. Wire.send(0x3C);

D. Wire.requestFrom(0x3C);

Solution

1. Step 1: Identify the function to start transmission

   Wire.beginTransmission(address) is used to begin sending data to the device at the given address.

2. Step 2: Check other options for correctness

   Wire.requestFrom() is for receiving data, Wire.send() is deprecated, and Wire.start() does not exist.

3. Final Answer:

   Wire.beginTransmission(0x3C); -> Option B

4. Quick Check:

   Use Wire.beginTransmission(address) to send data [OK]

Hint: Use Wire.beginTransmission(address) to start sending [OK]

Common Mistakes:

• Using Wire.requestFrom() to send data
• Using deprecated Wire.send() instead of Wire.write()
• Trying to use non-existent Wire.start() function

3. What will be the output of the following Arduino code snippet using the Wire library?

Wire.begin();
Wire.beginTransmission(0x50);
Wire.write(0x01);
Wire.endTransmission();
Wire.requestFrom(0x50, 1);
int data = Wire.read();
Serial.println(data);

medium

A. Prints the byte received from device at 0x50

B. Prints the byte 0x01

C. Prints 0 because Wire.read() returns 0 by default

D. Compilation error due to missing Wire.read()

Solution

1. Step 1: Analyze the code flow

   The code initializes I2C, sends one byte (0x01) to device 0x50, then requests 1 byte back from the same device.

2. Step 2: Understand Wire.read() behavior

   Wire.read() reads the byte received from the device. It does not return the sent byte but the device's response.

3. Final Answer:

   Prints the byte received from device at 0x50 -> Option A

4. Quick Check:

   Wire.read() returns received data, not sent data [OK]

Hint: Wire.read() reads incoming data, not what was sent [OK]

Common Mistakes:

• Assuming Wire.read() returns the sent byte
• Thinking Wire.read() returns 0 by default
• Confusing Wire.write() and Wire.read() roles

4. Identify the error in this Arduino I2C code snippet:

Wire.begin();
Wire.beginTransmission(0x40);
Wire.write(0x10);
Wire.requestFrom(0x40, 1);
Wire.endTransmission();
int val = Wire.read();

medium

A. Calling Wire.requestFrom() before Wire.endTransmission()

B. Missing Wire.beginTransmission() before Wire.write()

C. Using Wire.read() without requesting data

D. Not calling Wire.begin() to start I2C

Solution

1. Step 1: Check the order of I2C functions

   Wire.endTransmission() must be called to end sending data before requesting data with Wire.requestFrom().

2. Step 2: Identify the incorrect sequence

   The code calls Wire.requestFrom() before Wire.endTransmission(), which is incorrect and causes communication errors.

3. Final Answer:

   Calling Wire.requestFrom() before Wire.endTransmission() -> Option A

4. Quick Check:

   End transmission before requesting data [OK]

Hint: Always call Wire.endTransmission() before Wire.requestFrom() [OK]

Common Mistakes:

• Swapping the order of endTransmission and requestFrom
• Forgetting to call endTransmission() after beginTransmission()
• Calling Wire.read() without data available

5. You want to read 3 bytes from an I2C sensor at address 0x68 and store them in an array. Which code snippet correctly does this using the Wire library?

hard

A. Wire.beginTransmission(0x68);
for (int i = 0; i < 3; i++) {
data[i] = Wire.read();
}
Wire.endTransmission();

B. Wire.beginTransmission(0x68);
Wire.requestFrom(0x68, 3);
for (int i = 0; i < 3; i++) {
data[i] = Wire.read();
}
Wire.endTransmission();

C. Wire.requestFrom(0x68, 3);
for (int i = 0; i < 3; i++) {
data[i] = Wire.read();
}

D. Wire.requestFrom(0x68, 3);
Wire.endTransmission();
for (int i = 0; i < 3; i++) {
data[i] = Wire.read();
}

Solution

1. Step 1: Understand how to receive data with Wire.requestFrom()

   Wire.requestFrom(address, quantity) requests bytes from the device. Then Wire.read() reads each byte.

2. Step 2: Check the correct sequence for reading data

   Only Wire.requestFrom() is needed to receive data. Wire.beginTransmission() and Wire.endTransmission() are for sending data, not receiving.

3. Final Answer:

   Wire.requestFrom(0x68, 3); for (int i = 0; i < 3; i++) { data[i] = Wire.read(); } -> Option C

4. Quick Check:

   Use requestFrom() then read() in loop to get bytes [OK]

Hint: Use requestFrom() then read() in loop to get bytes [OK]

Common Mistakes:

• Using beginTransmission() when only reading data
• Calling endTransmission() after requestFrom()
• Reading data before requesting it