The i.MX93 provides three transmit/receive Serial Audio Interfaces (SAI).
On the ConnectCore 93 Development Kit, the SAI3 interface is connected to a Maxim 98089 low-power stereo codec with the following features:
-
Analog inputs: line-in A, line-in B, microphone:
-
Two line-in audio inputs through the LINE1_IN_L/R and LINE2_IN_L/R lines in the expansion connector.
-
Microphone audio input through the on-board jack connector.
-
-
Analog outputs: line-out, headphone, speakers:
-
Line-out audio output through the LINE_OUT_L/R lines in the expansion connector.
-
Headphone audio output through the on-board jack connector.
-
Speaker audio output through the SPKL_P/N and SPKR_P/N lines in the expansion connector.
-
-
Digital input/out multi-format audio interface.
-
Digital processing, filters, volume control, amplifiers.
The codec is a slave chip that the CPU controls via the SAI3 port of the ConnectCore 93 system-on-chip. The CPU drives audio data using the inter-IC sound bus standard (I2S).
All audio output comes out through this codec and can be reproduced using a pair of speakers or headphones.
Kernel configuration
You can manage the audio driver support through the following kernel configuration options:
-
Generic ASoC Sound Card with ASRC support (
CONFIG_SND_SOC_FSL_ASOC_CARD
) -
Maxim MAX98088/9 Low-Power, Stereo Audio Codec (
CONFIG_SND_SOC_MAX98088
)
These options are enabled as built-in on the default ConnectCore 93 kernel configuration file.
Kernel driver
The drivers for the audio interface and MAX98089 codec are located at:
File | Description |
---|---|
SAI driver |
|
Generic ASoC Sound Card with ASRC support |
|
Maxim MAX98088/9 Low-Power, Stereo Audio Codec |
Device tree bindings and customization
The SAI interface is documented at
Documentation/devicetree/bindings/sound/fsl,sai.yaml
.
The interface between the SAI and the codec is documented at
Documentation/devicetree/bindings/sound/fsl-asoc-card.txt
.
The MAX98088/9 codec is documented at
Documentation/devicetree/bindings/sound/max98088.txt
.
The device tree must contain entries for:
-
The SAI interface
-
The interface between the SAI and the audio codec
-
The audio codec
Example: SAI3 on ConnectCore 93 Development Kit
Definition of the SAI
sai3: sai@42660000 {
compatible = "fsl,imx93-sai";
reg = <0x42660000 0x10000>;
interrupts = <GIC_SPI 171 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clk IMX93_CLK_SAI3_IPG>, <&clk IMX93_CLK_DUMMY>,
<&clk IMX93_CLK_SAI3_GATE>,
<&clk IMX93_CLK_DUMMY>, <&clk IMX93_CLK_DUMMY>;
clock-names = "bus", "mclk0", "mclk1", "mclk2", "mclk3";
dmas = <&edma2 61 0 1>, <&edma2 60 0 0>;
dma-names = "rx", "tx";
status = "disabled";
};
/* Audio interface */
&sai3 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai3>;
assigned-clocks = <&clk IMX93_CLK_SAI3>;
assigned-clock-parents = <&clk IMX93_CLK_AUDIO_PLL>;
assigned-clock-rates = <12288000>;
fsl,sai-mclk-direction-output;
status = "okay";
};
[...]
/* Audio Interface */
pinctrl_sai3: sai3grp {
fsl,pins = <
MX93_PAD_GPIO_IO21__SAI3_TX_DATA00 0x31e
MX93_PAD_GPIO_IO20__SAI3_RX_DATA00 0x31e
MX93_PAD_GPIO_IO26__SAI3_TX_SYNC 0x31e
MX93_PAD_GPIO_IO16__SAI3_TX_BCLK 0x31e
MX93_PAD_GPIO_IO17__SAI3_MCLK 0x31e
>;
};
Interface between SAI and audio codec
sound_max98089: sound-max98089 {
compatible = "fsl,imx-audio-max98088";
model = "max98088-audio";
audio-cpu = <&sai3>;
audio-codec = <&max98089>;
audio-routing =
"Headphone Jack", "HPL",
"Headphone Jack", "HPR",
"Ext Spk", "SPKL",
"Ext Spk", "SPKR",
"Line Out Jack", "RECL",
"Line Out Jack", "RECR",
"Mic Jack", "MIC1",
"Mic Jack", "MIC2",
"Line In Jack", "INA1",
"Line In Jack", "INA2",
"Line In Jack", "INB1",
"Line In Jack", "INB2";
status = "okay";
};
Audio codec (LPI2C4 slave)
&lpi2c4 {
max98089: codec@10 {
compatible = "maxim,max98089";
reg = <0x10>;
clocks = <&clk IMX93_CLK_SAI3_GATE>;
clock-names = "mclk";
};
};
Use the audio interface
Audio controls
The audio codec is controlled from Linux via the ALSA framework. Digi Embedded Yocto provides an initial configuration that enables:
-
Line in A
-
Line in B
-
Microphone
-
Headphones
-
Speakers
-
Line out
You can use the command line application alsamixer
to manage these interfaces and their associated controls such as volume, gain, and filters.
Audio playback
Since all output routes are enabled by default, any sound will play on headphones, speakers, and line-out. |
To play a wav file:
# aplay sound.wav
To play an mp3 file using gstreamer:
# gst-launch-1.0 filesrc location=sound.mp3 ! id3demux ! queue ! beepdec ! alsasink
Audio recording
Since microphone, line-in A, and line-in B input routes are enabled by default, any recorded sound will mix the audio coming from these inputs. |
To record a stereo WAV audio file with 10 seconds duration from line-in:
# arecord -f cd sound.wav --duration 10
To record a mono WAV audio file from the microphone:
# arecord --format=S16_LE --channels=1 --rate=44100 micro.wav --duration=10