Mixer (Audio Mixer)

General Description

The Mixer driver provides APIs to configure the audio mixer.

The functions and other declarations used in this driver are in cy_mixer.h. You can include cy_pdl.h (ModusToolbox only) to get access to all functions and declarations in the PDL.

Features:

• Combines multiple PCM source streams into a single PCM destination stream.
• Typically, a PCM source stream consists of a repetition of a PCM sample pattern in memory. The number of repetitions is dynamic; that is, at the stream start, the stream end may not be known. Typically, a system event activates (starts) a PCM source stream and another system event deactivates (ends) a PCM source stream.
• A PCM source stream can be gain/volume controlled.
• A PCM source stream can be faded in (typically at the stream start) and faded out (typically just before the stream end).
• A PCM source stream sample frequency has a specific ratio with respect to the PCM destination stream sample frequency: 0.5x, 1x, 2x, 3x, 4x, 6x, 8x, 12x. The mixer upscales (2x, 3x, ..., 12x) or down-scales (0.5x) the PCM source stream to the PCM destination stream.
• The PCM destination stream can be gain/volume controlled.
• The PCM destination stream can be faded in and faded out.
• Fixed PCM sample formatting: 16-bit pairs.
• I2S transmitter with master and slave functionality. See the device datasheet to confirm whether this feature is supported.

Configuration Considerations

To set up an audio mixer, initialize the mixer destination and one or more source streams.

The mixer destination can be configured by providing all of the parameters in the cy_stc_mixer_dst_config_t structure. Then call the Cy_Mixer_DestinationInit function to initialize the mixer destination. Additional APIs are provided to configure and control the mixer destination after initialization.

A mixer source can be configured by providing all of the parameters in the cy_stc_mixer_src_config_t structure. Then call the Cy_Mixer_SourceInit function to initialize the mixer source. Additional APIs are provided to configure and control the mixer source after initialization.

For the mixer to operate, the destination and one or more sources must be enabled and activated. Typically, enabling a source is done at mixer initialization time and activating/deactivating a source is done at a finer grain, based on system events that activate (start) and/or deactivate (end) PCM source streams.

Destination initialization example:

    /* Scenario: Set up and start a mixer destination */
    cy_stc_mixer_dst_config_t config = {
        .fadeCode = CY_MIXER_CODE_SAME,
        .gainCode = 115,
        .trgLevel = 0,
    };

    /* Apply mixer destination configuration */
    Cy_Mixer_DestinationInit(MIXER0_MIXER_DST_STRUCT, &config);

    /* Enable the mixer destination */
    Cy_Mixer_Dst_Enable(MIXER0_MIXER_DST_STRUCT);

    /* Activate the mixer destination */
    Cy_Mixer_Dst_Activate(MIXER0_MIXER_DST_STRUCT);

Source initialization example:

    /* Scenario: Set up and start a mixer source */
    cy_stc_mixer_src_config_t config = {
        .fsRatio = CY_MIXER_SRC_FREQ_NO_RESAMPLE,
        .ch0sel = CY_MIXER_SRC_DATA_LOW,
        .ch1sel = CY_MIXER_SRC_DATA_HIGH,
        .fadeCode = CY_MIXER_CODE_MUTE,
        .gainCode = 115,
        .trgLevel = 0,
    };

    /* Apply mixer source configuration */
    Cy_Mixer_SourceInit(MIXER0_MIXER_SRC_STRUCT0, &config);

    /* Enable the mixer source */
    Cy_Mixer_Src_Enable(MIXER0_MIXER_SRC_STRUCT0);

    /* Activate the mixer source */
    Cy_Mixer_Src_Activate(MIXER0_MIXER_SRC_STRUCT0);

Mixer sources and destinations may be written and read by the MCU (via the provided APIs: Cy_Mixer_Src_FifoWriteData, Cy_Mixer_Dst_FifoReadData) or by DMA. If using DMA, the DMA channel should be previously configured. Triggers generated by the Mixer can be used to initiate DMA transfers to and from the mixer source and destination FIFOs.

More Information.

See the Mixer chapter of the device technical reference manual (TRM).

Changelog

Version	Changes	Reason for Change
1.0	The initial version.

API Reference
	Macros
	Functions
	Data Structures
	Enumerated Types