Inter-Integrated Circuit (I²C) Initialization and Configuration#

Overview#

The Silicon Labs WiSeConnect™ v3.x SDK provides a unified Inter-Integrated Circuit (I²C) driver API for SiWx917 devices. It supports multiple I²C instances with configurable operating modes, transfer flows (blocking and non-blocking), and power management features.

This guide walks through the complete initialization and configuration process for I²C communication.

For broader SDK topics, see WiSeConnect 3.

Startup Sequence#

Before using I²C, set up a project in Simplicity Studio and enable the I²C driver. In brief, you will:

1. Create or open a project.

2. Add the I²C component.

3. Configure instance, pins, speed, and addressing.

4. Generate the initialization code.

5. Build, flash, and test the result.

This section walks you through each step so you can bring up I²C quickly and verify the configuration on hardware.

Step-by-step I²C Initialization and Configuration in Simplicity Studio#

Step 1. Create or Open Your Project#

1. Launch Simplicity Studio.

2. Create a new project for your SiWx917 device, or open an existing one.

3. For a quick start, choose one of the I²C example projects from the WiSeConnect SDK.

4. Connect your SiWx917 radio board; Studio will auto-detect it.

   
   Figure: Board detection in Simplicity Studio

5. In Example Projects and Demos, search for I2C and open an example.

   
   Figure: Searching for I²C example projects

6. Click Create to add the project to your workspace. Review the example’s documentation for usage details.

7. After you confirm project details (name, location, link/copy SDK sources), Studio generates the project. Most examples automatically open the readme.md.

   

• Typical project layout:

  • autogen/ – Auto-generated files (configuration headers, linker scripts)

  • config/ – Platform-specific configuration headers

  • resources/ – Images and documentation assets

  • simplicity_sdk_/ – Gecko SDK platform and third-party libraries

  • platform/ – HAL, CMSIS-RTOS, and common libraries

  • wiseconnect3_sdk_/ – WiSeConnect SDK components and resources

  • app.c / app.h – Application sources

  • i2c_leader_example.c / i2c_leader_example.h – I²C leader example sources

  • main.c – Application entry point

  • readme.md – Example documentation and usage

  • sl_si91x_i2c_driver_leader.slcp – Project configuration file

  • sl_si91x_i2c_driver_leader.pintool – Pin configuration for I²C pins

  • sl_si91x_i2c_driver_leader.slps – Project set file for managing related solutions

Step 2. Add the I²C Component#

1. In your project’s .slcp configuration file, open the Software Components tab.

2. Search for I2C and add the required peripheral (for example, I2C0, I2C1, ULP_I2C). To add other instances, click Add New Instance.

   

Step 3. Configure I²C with Universal Configurator (UC)#

1. Click Configure to set up the I²C instance.

   

2. In the UC graphical interface, configure:

   • Mode: Leader or Follower.

   • Operating Speed: Standard, Fast, Fast Plus, or High Speed.

   • DMA (Direct Memory Access): Enable or disable.

   • Selected Module: Choose the module.

   • SCL/SDA: Select pins for the Serial Clock Line (SCL) and Serial Data Line (SDA).

• Possible pin combinations:

  • For I2C0 and I2C1:
    

  • For ULP_I2C:
    

• Pin selection methods in UC:

  • Select pins from a drop-down list:
    

  • Select pins using the Pin Tool:
    

Configuration Parameters#

Configuration Structure#

typedef struct {
  sl_i2c_mode_t mode;                    // Leader or Follower mode
  sl_i2c_operating_mode_t operating_mode; // Speed configuration
  sl_i2c_transfer_type_t transfer_type;   // Interrupt or DMA
  sl_i2c_callback_t i2c_callback;        // Callback function pointer
} sl_i2c_config_t;

Operating Modes#

typedef enum {
  SL_I2C_STANDARD_MODE = 1,    // 100 kHz
  SL_I2C_FAST_MODE = 2,        // 400 kHz
  SL_I2C_FAST_PLUS_MODE = 3,   // 1 MHz
  SL_I2C_HIGH_SPEED_MODE = 4   // 3.4 MHz
} sl_i2c_operating_mode_t;

Transfer Types#

typedef enum {
  SL_I2C_USING_INTERRUPT = 0,  // Blocking transfer
  SL_I2C_USING_DMA = 1         // Non-blocking DMA transfer
} sl_i2c_transfer_type_t;

I²C Modes#

typedef enum {
  SL_I2C_LEADER_MODE = 0,      // Leader (Master) mode
  SL_I2C_FOLLOWER_MODE = 1     // Follower (Slave) mode
} sl_i2c_mode_t;

Step 4. Generate Initialization Code#

When you add or modify I²C components, Simplicity Studio automatically adds the driver and configuration files.

• Click View Source in the UC configuration UI to view the generated configuration files.

  

Step 5. Initialize I²C in Your Application#

• Use WiSeConnect SDK APIs to initialize I²C. Driver source and header files are located at:

  /wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/inc/sl_si91x_i2c.h
  /wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/src/sl_si91x_i2c.c

• The I²C configuration structure is auto-generated in the autogen folder.

  

Example initialization code:

// Initializing I2C instance
i2c_status = sl_i2c_driver_init(i2c_instance, &sl_i2c_config);
DEBUGINIT();
if (i2c_status != SL_I2C_SUCCESS) {
  DEBUGOUT("sl_i2c_driver_init : Invalid Parameters, Error Code : %u \n", i2c_status);
} else {
  DEBUGOUT("Successfully initialized and configured I2C leader\n");
}
// Configuring RX and TX FIFO thresholds
i2c_status = sl_i2c_driver_configure_fifo_threshold(i2c_instance, I2C_TX_FIFO_THRESHOLD, I2C_RX_FIFO_THRESHOLD);
if (i2c_status != SL_I2C_SUCCESS) {
  DEBUGOUT("sl_i2c_driver_configure_fifo_threshold : Invalid Parameters, Error Code : %u \n", i2c_status);
} else {
  DEBUGOUT("Successfully configured I2C TX and RX FIFO thresholds\n");
}
// Enabling combined format transfer by enabling repeated start
i2c_status = sl_i2c_driver_enable_repeated_start(i2c_instance, true);
if (i2c_status != SL_I2C_SUCCESS) {
  DEBUGOUT("sl_i2c_driver_enable_repeated_start : Invalid Parameters, Error Code : %u \n", i2c_status);
} else {
  DEBUGOUT("Successfully enabled repeated start\n");
}

Step 6. Set Follower Address (if needed)#

For follower mode, set the device address using the appropriate API.

// Configuring follower mask address
i2c_status = sl_i2c_driver_set_follower_address(i2c_instance, OWN_I2C_ADDR);
if (i2c_status != SL_I2C_SUCCESS) {
  DEBUGOUT("sl_i2c_driver_init : Invalid Parameters, Error Code : %u \n", i2c_status);
} else {
  DEBUGOUT("Successfully configured I2C follower address\n");
}

Step 7. Customize for Advanced Use Cases#

Modify the generated configuration or initialization code for custom requirements (for example, callback functions or advanced DMA settings).

For more use cases, see I²C Usage Scenarios.

Step 8. Build, Flash, and Test#

After configuration, build the project, flash the firmware to the device, and test I²C operation. Simplicity Studio provides a built-in Virtual COM (VCOM) console for viewing logs.

Step-by-step: Build, Flash, and Test#

1. Build your project in Simplicity Studio.
   

2. Flash the firmware to the SiWx917 device.
   
   

3. Verify I²C operation using the serial console or debugger.

   Simplicity Studio provides a built-in VCOM console to view logs.

   • Connected devices view:
     

   • Connect devices:
     

   • Launch console:
     

   • View current launch settings:
     

   How to view logs:

   1. Open the console and select the serial1 tab.

   2. Place the cursor in the text entry field at the bottom.

   3. Press Enter to activate the console.

   • Follower log example:
     

   • Leader log example:
     

   Note: You can also use terminal programs such as Tera Term or PuTTY instead of the VCOM console.

References#

Related Example Projects

• WiSeConnect SDK I2C Peripheral Examples

  • SL Si91x – I2C Driver Follower

  • SL Si91x – I2C Driver Leader

  • SL Si91x – I2C Driver Leader Using Transfer API

  • SL Si91x – ULP I2C Leader