I2C Master - Communication Block

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BUS I2C MASTER Block The BUS I2C Master block configures and executes I2C (Inter-Integrated Circuit) communication sequences as a bus master. This block enables reading from and writing to I2C slave devices using a graphical sequence builder that supports complex multi-device transactions.

Block Inputs/Outputs

Inputs: Dynamic based on I2C sequence configuration

Outputs: Dynamic based on I2C sequence configuration

Dynamic Port Configuration

Block inputs and outputs are created based on the I2C sequence you configure:

• Read Data actions create output ports with the read data
• Write Data actions with block input enabled create input ports
• Write Address actions with block input enabled create address input ports
• Sequence Completed output available in non-blocking mode

Block Input/Output Datatype

Supported Device Families

Block Parameters

I2C Clock Speed

Clock speed is configured in the Initial Configuration action. Available frequencies depend on the peripheral clock:

The block automatically calculates the optimal I2CBRG register value for the requested frequency based on FCY.

Implementation Details

Sequence Execution

The I2C sequence is executed as a state machine:

1. Each action in the sequence is processed sequentially
2. Hardware interrupts handle byte-level timing
3. Completion status available in non-blocking mode

Buffer Management

Buffer sizes are automatically calculated from sequence configuration.

Device-Specific Implementations

Usage Examples

Example 1: Read Temperature Sensor (Single Register)

Typical sequence for reading a temperature sensor like TMP102:

1. Initial Configuration (400 kHz)
2. Start
3. Write Address: 0x48 (Write)
4. Write Data: 0x00 (temperature register)
5. Re-Start
6. Write Address: 0x48 (Read)
7. Read Data: 2 bytes → Output "Temperature"
8. Stop

Example 2: Write EEPROM Data

Write data to an I2C EEPROM:

1. Initial Configuration (400 kHz)
2. Start
3. Write Address: 0x50 (Write)
4. Write Data: [HighAddr, LowAddr] (memory address)
5. Write Data: [Data1, Data2, ...] (from block input)
6. Stop

Example 3: Multi-Device Transaction

Read from multiple sensors in one sequence:

1. Initial Configuration (400 kHz)
2. Start
3. Write Address: Device1
4. Read Data → Output "Sensor1"
5. Re-Start
6. Write Address: Device2
7. Read Data → Output "Sensor2"
8. Stop

Troubleshooting

I2C Not Communicating

Problem: No data on I2C bus.

Solutions:

• Verify SDA and SCL pin assignments match hardware
• Check pull-up resistors on SDA and SCL lines (typically 4.7kΩ)
• Verify slave device address (7-bit, not 8-bit with R/W)
• Check clock frequency compatibility with slave device

NAK Received

Problem: Slave returns NAK (no acknowledge).

Solutions:

• Verify slave address is correct
• Check if slave device is powered and responding
• Ensure addressing mode (7/10-bit) matches slave
• Check for bus contention with other masters

Clock Stretching Timeout

Problem: Slave stretches clock too long.

Solutions:

• Increase timeout settings if available
• Verify slave device operation
• Check for firmware issues on slave device

Pin Warning Messages

Problem: “I2C Port SCL/SDA not available” warning.

Solutions:

• I2C pins are fixed on many devices - check datasheet
• Verify correct alternate pin selection via fuses
• Some chips have alternate I2C pin options (ASCL, ASDA)

See Also

• Communication Blocks Overview
• SPI Block
• UART Configuration
• CAN Configuration