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# src/intent_engine

This folder contains the intent engine module for the low power FFD application.

Table 32 Low Power FFD Intent Engine
Filename/Directory | Description
--- | ---
intent_engine_io.c | contains additional io intent engine code
intent_engine_support.c | contains general intent engine support code
intent_engine.c | contains the implementation of default intent engine code
intent_engine.h | header for intent engine code

## Major Components

The intent engine module provides the application with the following primary API functions:

Listing 21 Intent Engine API (intent_engine.h)

    int32_t intent_engine_create(uint32_t priority, void *args);
    void intent_engine_ready_sync(void);
    int32_t intent_engine_sample_push(asr_sample_t *buf, size_t frames);

These APIs provide the functionality needed to feed audio pipeline samples into the ASR engine.

### intent_engine_create

This function has the role of creating the model running task and providing a pointer, which can be used by the application to handle the output intent result. In the case of the default configuration, the application provides a FreeRTOS Queue object.

In Low Power FFD, the audio pipeline output is on tile 1 and the ASR engine on tile 0.

Listing 22 intent_engine_create snippet (intent_engine_io.c)

    intent_engine_intertile_task_create(priority);

The call to intent_engine_intertile_task_create() will create two threads on tile 0. One thread is the ASR engine thread. The other thread is an intertile RX thread, which will interface with the audio pipeline output.

### intent_engine_ready_sync

This function is called by both tiles and serves to ensure that tile 0 is ready to receive audio samples before starting the audio pipeline. This is a preventative measure to avoid dropping samples at startup.

Listing 23 intent_engine_create snippet (intent_engine_io.c)

        int sync = 0;
    #if ON_TILE(AUDIO_PIPELINE_OUTPUT_TILE_NO)
        size_t len = rtos_intertile_rx_len(intertile_ctx, appconfINTENT_ENGINE_READY_SYNC_PORT, RTOS_OSAL_WAIT_FOREVER);
        xassert(len == sizeof(sync));
        rtos_intertile_rx_data(intertile_ctx, &sync, sizeof(sync));
    #else
        rtos_intertile_tx(intertile_ctx, appconfINTENT_ENGINE_READY_SYNC_PORT, &sync, sizeof(sync));
    #endif

### intent_engine_sample_push

This function has the role of sending the ASR output channel from the audio pipeline to the intent engine.

In Low Power FFD, the audio pipeline output is on tile 1 and the ASR engine on tile 0.

Listing 24 intent_engine_create snippet (intent_engine_io.c)

        intent_engine_samples_send_remote(
                intertile_ap_ctx,
                frames,
                buf);

The call to intent_engine_samples_send_remote() will send the audio samples to the previously configured intertile RX thread.

### intent_engine_process_asr_result

This function can be replaced by the application to handle the intent in a completely different manner.

## Low Power Components

The following APIs are the intent engine mechanisms needed by the power control task.

Listing 25 Low Power APIs (intent_engine.h)

    void intent_engine_full_power_request(void);
    void intent_engine_low_power_accept(void);

In this implementation, it is the responsibility of tile 0 (intent engine tile) to determine when to request a transition into low power mode; however, tile 1 may reject the request. When tile 1 accepts the request (via LOW_POWER_ACK), the power control task calls intent_engine_low_power_accept. When tile 1 rejects the request (via LOW_POWER_NAK), the power control task calls intent_engine_full_power_request.

Note

There is an additional LOW_POWER_HALT response where the power control task calls intent_engine_halt. This is primarily for end-of-evaluation handling logic for the underlying ASR engine and is not needed for a normal application.

After tile 1 accepts the low power request, tile 0 begins preparations for entering low power by locking various resources and waiting for any enqueued commands to finish up. The helper functions below are provided for this purpose.

Listing 26 Low Power Helper Functions (intent_engine.h)

    int32_t intent_engine_keyword_queue_count(void);
    void intent_engine_keyword_queue_complete(void);
    uint8_t intent_engine_low_power_ready(void);

Before tile 1 sends LOW_POWER_ACK it also stops pushing audio samples via intent_engine_sample_push. After receiving the low power response, the application may clear the stream buffer and keyword queue to avoid processing stale samples/commands when returning to full power mode. The functions below provide this functionality.

Listing 27 Low Power Helper Functions (intent_engine.h)

    void intent_engine_keyword_queue_reset(void);
    void intent_engine_stream_buf_reset(void);

Note

Since it is possible that a command is spoken/recognized between the time when tile 0 requests low power and when tile 1 responds to the request, the application should not reset these buffer entities until it has received LOW_POWER_ACK; otherwise, recognized commands may be lost.

## Evaluation Specific Components

The following functions are provided for the primary purpose of facilitating the evaluation of the ASR model. The provided ASR models have evaluation periods which will end due to various factors. When the evaluation period ends, the application logic halts the intent engine via intent_engine_halt. This is primarily to ensure the device remains in full-power mode to allow functionality that may be exclusive to tile 0 to function.

Listing 28 Evaluation-specific Helper Functions (intent_engine.h)

    void intent_engine_halt(void);