Inter-IC Sound (I²S) Initialization and Configuration#

The WiSeConnect software development kit (SDK) provides a unified Inter-IC Sound (I²S) driver application programming interface (API) for SiWx917 devices. The driver supports multiple I²S instances with configurable operating modes, transfer types, and power-management features.

This guide walks you through the complete initialization and configuration process for I²S communication, from project setup to verification on hardware.

Step 1. Create or Open a Project#

1. Launch Simplicity Studio.

2. Create a new SiWx917 project or open an existing one.

3. For a quick start, start from a WiSeConnect I²S example:

   • sl_si91x_i2s_primary

   • sl_si91x_i2s_secondary

   • sl_si91x_i2s_loopback

   • sl_si91x_ulp_i2s

4. Connect the SiWx917 radio board. Simplicity Studio detects it automatically and shows it in Connected Devices.

   
   Figure: Board detection in Simplicity Studio

5. From Example Projects and Demos, search for I2S, select an example, and click Create.

   
   Figure: Searching for I²S example projects in Simplicity Studio

6. Review the example’s readme.md for supported hardware and expected console output.

Typical Project Structure#

• autogen/ – Auto-generated configuration headers and linker scripts

• config/ – Platform-specific configuration headers

• resources/ – Images and documentation assets

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

• wiseconnect3_sdk_4.0.0/ – WiSeConnect SDK components and resources

• sl_si91x_i2s_primary.slcp – Project configuration file

• sl_si91x_i2s_primary.pintool – Pin Tool configuration for I²S pins

• app.c / app.h – Application source and header files

• main.c – Application entry point

• readme.md – Example documentation and usage instructions

Step 2. Add the I²S Component#

If your project does not already include I²S:

1. Open the project’s .slcp file.

2. Go to the Software Components tab.

3. Search for I2S.

4. Add the required instances, for example:

   • I2S0 for HP audio

   • ULP_I2S for low-power audio

5. To add more instances, select Add New Instance.

Simplicity Studio pulls in driver code and configuration automatically.

Figure: Adding the I²S component in Simplicity Studio

Step 3. Configure I²S with Universal Configurator (UC)#

1. In the Software Components view, select the I²S instance and click Install (if not already installed).

2. Click Configure to open Universal Configurator (UC).

3. Set the key parameters:
   

   Parameter	Description	Options / Range
   Resolution	Bits per audio sample	16, 24, or 32 bits
   Channel	Channel instance	Channel 0, Channel 1
   Sampling rate	Audio sample rate	8 kHz – 192 kHz
   Selected module	I²S hardware instance	I2S0
   DIN (data in)	Audio data input pin	GPIO_XX
   DOUT (data out)	Audio data output pin	GPIO_XX
   SCLK (bit clock)	Serial clock pin	GPIO_XX
   WSCLK (word select / LR clock)	Left-right channel clock pin	GPIO_XX

4. Use the Pin Tool view to verify and adjust pin routing as needed.

   • Select pins from the drop-down list in UC.

   • Configure pin routing using the Pin Tool.

     
     Figure: Recommended I²S pin selections

     
     Figure: Recommended ULP I²S pin selections

   • UC stores these settings in auto-generated configuration files under autogen/.

Step 4. Configuration Parameters and Data Structures#

The I²S driver uses configuration structures and enums to describe operating mode, protocol, and transfer parameters.

Example Transfer Configuration#

typedef struct {
  uint16_t mode;          // Primary (controller) or Secondary (target) mode
  uint16_t sync;          // Synchronous or Asynchronous mode
  uint16_t protocol;      // Protocol (I²S or PCM)
  uint16_t resolution;    // Audio data resolution
  uint32_t data_size;     // Data word size (bits)
  uint32_t sampling_rate; // Audio sampling rate (Hz)
  uint32_t transfer_type; // Transfer type (Transmit or Receive)
} sl_i2s_xfer_config_t;

Example Event Enumeration#

typedef enum {
  SL_I2S_SEND_COMPLETE    = ARM_SAI_EVENT_SEND_COMPLETE,    // Send complete event
  SL_I2S_RECEIVE_COMPLETE = ARM_SAI_EVENT_RECEIVE_COMPLETE, // Receive complete event
  SL_I2S_TX_UNDERFLOW     = ARM_SAI_EVENT_TX_UNDERFLOW,     // DOUT underrun event
  SL_I2S_RX_OVERFLOW      = ARM_SAI_EVENT_RX_OVERFLOW,      // DIN overflow event
  SL_I2S_FRAME_ERROR      = ARM_SAI_EVENT_FRAME_ERROR       // Frame error event
} i2s_event_typedef_t;

Power States and Modes#

typedef enum {
  SL_I2S_POWER_OFF  = ARM_POWER_OFF,  // Power off mode
  SL_I2S_FULL_POWER = ARM_POWER_FULL  // Full power mode
} sl_i2s_power_state_t;

typedef enum {
  SL_I2S_MASTER = ARM_SAI_MODE_MASTER, // I²S primary (controller) mode
  SL_I2S_SLAVE  = ARM_SAI_MODE_SLAVE   // I²S secondary (target) mode
} sl_i2s_mode_t;

Step 5. Autogenerated Initialization Code#

When you add or modify I²S components, Simplicity Studio automatically generates configuration and driver files.

• In the UC interface, click View Source to inspect the generated code.

  Figure: Auto-generated I²S initialization code in UC

Step 6. Initialize I²S in Your Application#

Use WiSeConnect SDK APIs to initialize and configure I²S. The driver source and header files are located in:

/wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/inc/sl_si91x_i2s.h
/wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/src/sl_si91x_i2s.c

Example Initialization Code#

status = sl_si91x_i2s_init(I2S_INSTANCE, &i2s_driver_handle);
if (status != SL_STATUS_OK) {
  DEBUGOUT("I²S initialization failed. Error code: %u\r\n", status);
} else {
  DEBUGOUT("I²S initialization successful.\r\n");
}

// Configure full power mode
status = sl_si91x_i2s_configure_power_mode(i2s_driver_handle, SL_I2S_FULL_POWER);
if (status != SL_STATUS_OK) {
  DEBUGOUT("I²S power mode configuration failed.\r\n");
} else {
  DEBUGOUT("I²S power mode configuration successful.\r\n");
}

// Register user callback
status = sl_si91x_i2s_register_event_callback(i2s_driver_handle, callback_event);
if (status != SL_STATUS_OK) {
  DEBUGOUT("I²S callback registration failed.\r\n");
} else {
  DEBUGOUT("I²S callback registration successful.\r\n");
}

Step 7. Customize for Advanced Use Cases#

You can modify the generated configuration or initialization code to support advanced scenarios, such as:

• User-defined callback handlers

• Dynamic DMA channel allocation

• Power-state-based reinitialization

For additional examples, see the I²S Usage Scenarios.

Step 8. Build, Flash, and Test#

After configuration, build and flash the firmware to your SiWx917 device. Use the VCOM console in Simplicity Studio or an external terminal application to monitor logs and verify I²S operation.

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

1. Build the project in Simplicity Studio.
   

2. Flash the firmware to the SiWx917 device.
   
   

3. Verify I²S operation using the serial console or debugger.

   • Connected devices view:

   • Connect devices:

   • Launch console:

   • View console settings:

   • Console logs for Primary and Secondary:

     How to view logs:

     1. Open the console and select the serial1 tab.

     2. Place the cursor in the input field at the bottom.

     3. Press Enter to activate the console.

     Primary log example:
     Secondary log example:
     

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

References#

Related Example Projects

• WiSeConnect SDK I²S Peripheral Examples

  • SL Si91x – I2S Loopback

  • SL Si91x – I2S Primary

  • SL Si91x – I2S Secondary

  • SL Si91x – ULP I2S