Connecting multiple I2C devices in Arduino - Step-by-Step Execution

Concept Flow - Connecting multiple I2C devices

Start I2C Bus

↓

Scan for Devices

↓

Identify Device Addresses

↓

Connect Devices with Unique Addresses

↓

Communicate with Each Device

↓

Handle Data Separately

↓

End Communication

This flow shows how the Arduino starts the I2C bus, finds devices, connects to each with unique addresses, and communicates with them one by one.

Execution Sample

Arduino

Wire.begin();
Wire.beginTransmission(0x3C);
Wire.write(0x00);
Wire.endTransmission();
Wire.beginTransmission(0x68);
Wire.write(0x00);
Wire.endTransmission();

This code initializes I2C, then sends data to two devices with addresses 0x3C and 0x68 separately.

Execution Table

Step	Action	Device Address	Data Sent	Result
1	Initialize I2C bus	-	-	Bus ready
2	Begin transmission	0x3C	-	Started communication with device 0x3C
3	Write data	0x3C	0x00	Data queued for device 0x3C
4	End transmission	0x3C	-	Data sent to device 0x3C
5	Begin transmission	0x68	-	Started communication with device 0x68
6	Write data	0x68	0x00	Data queued for device 0x68
7	End transmission	0x68	-	Data sent to device 0x68

💡 All devices communicated with separately using their unique addresses.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7
currentDevice	none	0x3C	0x3C	none	0x68	0x68	none
dataBuffer	empty	empty	0x00	empty	empty	0x00	empty

Key Moments - 2 Insights

Why do we need to use different addresses for each I2C device?

Each device on the I2C bus must have a unique address so the Arduino knows which device to talk to, as shown in steps 2 and 5 where different addresses 0x3C and 0x68 are used.

Can we send data to multiple devices at the same time on I2C?

No, the Arduino communicates with one device at a time by starting and ending transmission separately for each device, as seen in steps 2-4 and 5-7.

Visual Quiz - 3 Questions

Look at the execution table, what device address is used at step 5?

A 0x3C

B 0x68

C 0x00

D No device

💡 Hint

Check the 'Device Address' column at step 5 in the execution_table.

At which step is data actually sent to the device 0x3C?

A Step 4

B Step 2

C Step 3

D Step 5

💡 Hint

Look for 'End transmission' action for device 0x3C in the execution_table.

If both devices had the same address, what would happen in the communication?

A Both devices receive data correctly

B Arduino stops communication

C Only one device responds, causing conflicts

D Data is sent to a new address automatically

💡 Hint

Recall the key moment about unique addresses and how Arduino communicates with one device at a time.

Concept Snapshot

Connecting multiple I2C devices:
- Each device must have a unique address.
- Use Wire.begin() to start I2C.
- Communicate by beginTransmission(address), write(data), endTransmission().
- Talk to devices one at a time.
- Addresses avoid conflicts on the bus.

Full Transcript

This lesson shows how to connect multiple I2C devices to an Arduino. The Arduino starts the I2C bus with Wire.begin(). It then communicates with each device separately by using the device's unique address. For example, it sends data to device 0x3C first, then to device 0x68. Each communication starts with beginTransmission(address), then data is written, and finally endTransmission() sends the data. Devices must have different addresses so the Arduino knows who to talk to. The execution table shows each step clearly. This method avoids conflicts and ensures each device gets the right data.