How-Tos

This section includes instructions on anticipated or common software modifications.

Changing the input and output sample rate

In the example design app_conf.h file, change appconfAUDIO_PIPELINE_SAMPLE_RATE to either 16000 or 48000.

I²S AEC reference input audio & USB processed audio output

The FFVA example design includes 2 basic configurations; INT and UA. The INT configuration is setup with I²S for input and output audio. The UA configuration is setup with USB for input and output audio. This HOWTO explains how to modify the FFVA example design for I²S input audio and USB output audio.

In the ffva_ua.cmake file, changing the appconfAEC_REF_DEFAULT to appconfAEC_REF_I2S will result in the expected input frames.

set(FFVA_UA_COMPILE_DEFINITIONS
    ${APP_COMPILE_DEFINITIONS}
    appconfI2S_ENABLED=1
    appconfUSB_ENABLED=1
    appconfAEC_REF_DEFAULT=appconfAEC_REF_I2S

    appconfI2S_MODE=appconfI2S_MODE_MASTER
    MIC_ARRAY_CONFIG_MCLK_FREQ=24576000
)

For integrating with I²S there are a few other differences from the default UA configuration. When integrating with an external Raspberry Pi BCLK and LRCLK, you will want the following FFVA_UA_COMPILE_DEFINITIONS:

set(FFVA_UA_COMPILE_DEFINITIONS
    ${APP_COMPILE_DEFINITIONS}
    appconfI2S_ENABLED=1
    appconfUSB_ENABLED=1
    appconfAEC_REF_DEFAULT=appconfAEC_REF_I2S

    appconfI2S_MODE=appconfI2S_MODE_SLAVE
    appconfEXTERNAL_MCLK=0
    appconfI2S_AUDIO_SAMPLE_RATE=48000
    MIC_ARRAY_CONFIG_MCLK_FREQ=12288000
)

appconfI2S_AUDIO_SAMPLE_RATE can also be 16000. Only 48k and 16k conversions is supported in FFVA.

The default FFVA INT device doesn’t require an external MCLK, but this setting can be changed by setting appconfEXTERNAL_MCLK=1. In this case the FFVA example application will sit at initialization until it can lock on to that clock source, so it MUST be active during boot.

Since the FFVA example application is not receiving reference audio through USB in this configuration, USB adaptive mode will not adapt to the input. By default, FFVA will output the configured nominal rate.

If you enable appconfAEC_REF_DEFAULT=appconfAEC_REF_I2S and appconfI2S_MODE=appconfI2S_MODE_MASTER. You need to invert I2S_DATA_IN and I2S_MIC_DATA in the bsp_config/XK_VOICE_L71/XK_VOICE_L71.xn file to have the reference audio play properly.

Lastly, with I²S enabled the DAC is always initialized by the FFVA example application. If FFVA cannot be the I²C host then it is up to the host to initialize the DAC, like in the AVS demo.