Pulse Code Modulation (PCM) Initialization and Configuration#

This section explains how to initialize and configure the Pulse Code Modulation (PCM) peripheral on SiWx917 devices using Simplicity Studio, the WiSeConnect software development kit (SDK), and the Universal Configurator (UC).

You will learn how to:

• Create a PCM-enabled project

• Add and configure PCM components

• Set sample rate, bit depth, and clocking modes

• Assign pins for FSYNC, BCLK, DIN, and DOUT

• Initialize PCM in code and validate transfers using blocking or DMA modes

PCM operates in the high-performance (HP) domain and is intended for synchronous, low-latency audio applications such as voice paths, telephony interfaces, or external DSP communication.

Step 1. Create or Open a Project#

1. Launch Simplicity Studio and connect a supported SiWx917 evaluation board.
   
   Figure: Board detection in Simplicity Studio

2. Create a new project or open an existing one based on one of the following WiSeConnect PCM examples:

   • sl_si91x_pcm_primary

   • sl_si91x_pcm_secondary

   • sl_si91x_pcm_loopback

3. Select an example and click Create to import it.
   Figure: Search example PCM projects

4. Review the included readme.md for wiring and board-specific notes.

Typical directory structure

• 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_4.0.0/ – WiSeConnect SDK components and resources

  • components/ – Wi-Fi, BLE, Si91x MCU subsystem

• sl_si91x_pcm_primary.slcp – Project configuration file

• sl_si91x_pcm_primary.slps – Project set file

• sl_si91x_pcm_primary.pintool – Pin configuration for PCM pins

• app.c, app.h, main.c – Application sources

• readme.md – Example documentation and usage

Step 2. Add the PCM Component#

1. Open the project’s .slcp file.

2. Select Software Components.

3. Search for PCM, or navigate to WiSeConnect SDK → Device → Si91x → MCU → Peripherals → PCM.

4. Install the PCM component.

5. To add more instances, click Add New Instance (for example, PCM0).

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

Click Install, then Configure to set up the PCM instance.

UC Parameters#

Pin selection

• Choose pins from the drop-down list:
  

• Or use the Pin Tool:
  

Step 4. (Optional) Configure in Code#

You can refine the generated configuration in application code, such as:

• PCM mode

• resolution and sampling rate

• transfer type

Refer to the PCM API Reference for configuration structure and enumeration definitions.

Terminology Note:
In signal names, use DIN (data in) and DOUT (data out).

Step 5. Generate Initialization Code#

When you add or modify PCM components, Simplicity Studio generates the driver and configuration files.

• In the UC configuration UI, select View Source to review the generated files.

Step 6. Initialize PCM in Your Application#

Driver locations

/wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/inc/sl_si91x_pcm.h
/wiseconnect3_sdk_<version>/components/device/silabs/si91x/mcu/drivers/unified_api/src/sl_si91x_pcm.c

Example

sl_status_t status;
sl_i2s_handle_t pcm_handle;     // Handle type as defined by the SDK
uint32_t pcm_sampling_frequency = SL_I2S_SAMPLING_RATE_16000;
uint32_t pcm_resolution         = SL_I2S_RESOLUTION_16;
uint16_t mode                   = SL_I2S_MASTER;

void callback_event(uint32_t event);

status = sl_si91x_pcm_init(PCM_INSTANCE, &pcm_handle);
if (status != SL_STATUS_OK) {
  DEBUGOUT("PCM Initialization fail\r\n");
  // handle error
} else {
  DEBUGOUT("PCM Initialization success\r\n");
}

status = sl_si91x_pcm_register_event_callback(pcm_handle, callback_event);
if (status != SL_STATUS_OK) {
  DEBUGOUT("PCM user callback register fail\r\n");
  // handle error
} else {
  DEBUGOUT("PCM user callback register success\r\n");
}

status = sl_si91x_pcm_set_configuration(pcm_handle, pcm_sampling_frequency, pcm_resolution, mode);
if (status != SL_STATUS_OK) {
  DEBUGOUT("PCM configuration set fail\r\n");
  // handle error
} else {
  DEBUGOUT("PCM configuration set success\r\n");
}

Step 7. Build, Flash, and Test#

Step-by-step

1. Build your project in Simplicity Studio.

2. Flash the firmware to your Si91x device.
   
   

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

   • 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.

Primary log example

Secondary log example

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

Reference#

• Structure reference: sl_i2s_xfer_config_t

Related example projects

• WiSeConnect SDK PCM peripheral examples

  • SL Si91x – PCM Loopback

  • SL Si91x – PCM Primary

  • SL Si91x – PCM Secondary