2021 Microchip Technology Inc. DS00003118C-Page 43
AN3118
5.0 AUDIO MIXER MODE
During standalone mode, the MSPK v1.3 software (or
onwards) provides an audio mixer mode to mix A2DP
audio (SBC/AAC) with either one of an I
2
S-in, Aux-in or
Microphone. The audio mixer is not supported under
LDAC streaming.
During the mixer mode, the Audio effect and Audio
SRC can be enabled for the A2DP audio path. ADC
Gain is provided for the Aux-in and Microphone-in while
the speaker gain is provided for the analog audio
output, as shown in the following figure.
FIGURE 43: AUDIO PATH
When there is A2DP streaming and an input source
(one of I
2
S-in, Aux-in or Mic-in), the system will enter
audio mixer mode when the audio mixer is enabled.
Otherwise, if there is only A2DP streaming, the system
stays in A2DP mode. If there is only an input source, it
stays in line-in mode. Both Config GUI tools and UART
command can enable the audio mixer and select one of
the audio sources as an input. Audio mixer mode is
available in Standalone mode but not in Concert or
Stereo mode.
The audio mixer either mixes 44.1K or 48 KHz audio.
When A2DP is 44.1 KHz, the I
2
S in/Microphone in need
to be 44.1 KHz. On the other hand, when A2DP is 48
KHz, the I
2
S in/Microphone is 48 KHz. Audio SRC can
be enabled before the mixer to provide 48 KHz audio;
I
2
S-in and Microphone-in need to be 48 KHz.
The audio mixer mode is available both in Host mode
and Embedded mode. Under Host mode, the UART
command MMI action 0x80 is to enable the mixer while
0x81 is to disable dynamically. MMI action 0x82 and
0x83 adjust the “ADC gain” up and down respectively.
For more details, refer to Appendix V: “Audio Mixer
Settings” and AudioUARTCommdnSet_v2.08 (or
above).
SBC/AAC
Decoder
Equalizer
Audio
Effect
Audio
SRC
Audio
Mixer
OR
Internal DAC
Speaker Gain
ORI2S-In
Aux-In
Mic-In
Analog
Audio Output
I2S Audio Output
ADC
Gain
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