src#

This folder contains the core application source.

Table 14 FFD src#
Filename/Directory	Description
audio_pipeline directory	contains example XMOS audio pipeline
gpio_ctrl directory	contains general purpose input handling and LED handling tasks
intent_engine directory	contains intent engine code
intent_handler directory	contains intent handling code
power directory	contains low power state and control code
rtos_conf directory	contains default FreeRTOS configuration headers
app_conf_check.h	header to validate app_conf.h
app_conf.h	header to describe app configuration
config.xscope	xscope configuration file
ff_appconf.h	default fatfs configuration header
main.c	main application source file
xcore_device_memory.c	model loading from filesystem source file
xcore_device_memory.h	model loading from filesystem header file

Audio Pipeline#

The audio pipeline module provides the application with three API functions:

Listing 1 Audio Pipeline API (audio_pipeline.h)#

void audio_pipeline_init(
        void *input_app_data,
        void *output_app_data);

void audio_pipeline_input(
        void *input_app_data,
        int32_t **input_audio_frames,
        size_t ch_count,
        size_t frame_count);

int audio_pipeline_output(
        void *output_app_data,
        int32_t **output_audio_frames,
        size_t ch_count,
        size_t frame_count);

audio_pipeline_init#

This function has the role of creating the audio pipeline, with two optional application pointers which are provided to the application in the audio_pipeline_input() and audio_pipeline_output() callbacks.

In FFD, the audio pipeline is initialized with no additional arguments, and instantiates a 3 stage pipeline on tile 1, as described in: Audio Pipeline

audio_pipeline_input#

This function has the role of providing the audio pipeline with the input frames.

This function is weak so the application can override it if desired.

In FFD, the input is received from the rtos_mic_array driver.

audio_pipeline_output#

This function has the role of receiving the processed audio pipeline output.

This function is weak so the application can override it if desired.

In FFD, the output is sent to the intent engine. If appconfLOW_POWER_ENABLED is set true, then the output will be dropped if the power state is not POWER_STATE_FULL. In certain conditions and environments, this behavior may cause the wake word to be missed. Further adjustments to the application configuration settings related to the VNR low power thresholds may mitigate such issues. See src/power.

Main#

The major components of main are:

Listing 2 Main components (main.c)#

void startup_task(void *arg)
void vApplicationMinimalIdleHook(void)
void tile_common_init(chanend_t c)
void main_tile0(chanend_t c0, chanend_t c1, chanend_t c2, chanend_t c3)
void main_tile1(chanend_t c0, chanend_t c1, chanend_t c2, chanend_t c3)

startup_task#

This function has the role of launching tasks on each tile. For those familiar with XCORE, it is comparable to the main par loop in an XC main.

vApplicationMinimalIdleHook#

This is a FreeRTOS callback. By calling “waiteu” without events configured, this has the effect of both MIPs and power savings on XCORE.

Listing 3 vApplicationMinimalIdleHook (main.c)#

asm volatile("waiteu");

tile_common_init#

This function is the common tile initialization, which initializes the bsp_config, creates the startup task, and starts the FreeRTOS kernel.

main_tile0#

This function is the application C entry point on tile 0, provided by the SDK.

main_tile1#

This function is the application C entry point on tile 1, provided by the SDK.