The {cpu-family} provides two transmit/receive Serial Audio Interfaces (SAI) and another two receive-only SAIs.
On the ConnectCore 8X SBC Pro, the SAI0 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_ and LINE2_IN_ lines of the expansion connector.
-
Microphone audio input through the MIC_ lines of the expansion connector.
-
-
Analog outputs: line-out, headphone, speakers:
-
Line-out audio output through the LINE_OUT_ lines of the expansion connector.
-
Headphone audio output through the on-board jack connector.
-
Speaker audio output through the SPKL_ and SPKR_ lines of 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 SAI0 port of the ConnectCore 8X 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:
-
SoC Audio for NXP i.MX CPUs (
CONFIG_SND_IMX_SOC
) -
SoC Audio support for i.MX boards with max98088/max98089 (
CONFIG_SND_SOC_IMX_MAX98088
)
These options are enabled as built-in on the default ConnectCore 8X kernel configuration file.
Kernel driver
The drivers for the audio interface and MAX98089 codec are located at:
File | Description |
---|---|
SAI driver |
|
Driver interface with codec |
|
MAX98088/9 codec driver |
Device tree bindings and customization
The SAI interface is documented at
Documentation/devicetree/bindings/sound/fsl-sai.txt
.
The interface between the SAI and the codec is documented at
Documentation/devicetree/bindings/sound/imx-audio-max98088.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: SAI0 on ConnectCore 8X SBC Pro
Definition of the SAI
[...]
sai0: sai@59040000 {
compatible = "fsl,imx8qm-sai";
reg = <0x59040000 0x10000>;
interrupts = <GIC_SPI 314 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&sai0_lpcg 1>,
<&clk_dummy>,
<&sai0_lpcg 0>,
<&clk_dummy>,
<&clk_dummy>;
clock-names = "bus", "mclk0", "mclk1", "mclk2", "mclk3";
dma-names = "rx", "tx";
dmas = <&edma0 12 0 1>, <&edma0 13 0 0>;
power-domains = <&pd IMX_SC_R_SAI_0>,
<&pd IMX_SC_R_AUDIO_CLK_0>,
<&pd IMX_SC_R_AUDIO_CLK_1>,
<&pd IMX_SC_R_AUDIO_PLL_0>,
<&pd IMX_SC_R_AUDIO_PLL_1>;
status = "disabled";
};
[...]
&sai0 {
assigned-clocks = <&clk IMX8QXP_AUD_PLL0_DIV>,
<&clk IMX8QXP_AUD_ACM_AUD_PLL_CLK0_DIV>,
<&clk IMX8QXP_AUD_ACM_AUD_REC_CLK0_DIV>,
<&clk IMX8QXP_AUD_SAI_0_MCLK>;
assigned-clock-rates = <786432000>, <49152000>, <12288000>, <49152000>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai0>;
status = "okay";
};
[...]
/* IOMUX */
&iomuxc {
[...]
pinctrl_sai0: sai0grp {
fsl,pins = <
SC_P_SAI0_RXD_ADMA_SAI0_RXD 0x06000040
SC_P_SAI0_TXD_ADMA_SAI0_TXD 0x06000060
SC_P_SAI0_TXFS_ADMA_SAI0_TXFS 0x06000040
SC_P_SAI0_TXC_ADMA_SAI0_TXC 0x06000040
SC_P_SPI3_CS0_ADMA_ACM_MCLK_OUT1 0x06000040
>;
};
[...]
};
Interface between SAI and audio codec
[...]
sound_max98089: sound-max98089 {
compatible = "fsl,imx-audio-max98088";
model = "imx-max98088";
cpu-dai = <&sai0>;
audio-codec = <&max98089>;
asrc-controller = <&asrc0>;
audio-routing =
"Headphone Jack", "HPL",
"Headphone Jack", "HPR",
"Ext Spk", "SPKL",
"Ext Spk", "SPKR",
"LineOut", "RECL",
"LineOut", "RECR",
"Mic1", "MIC1",
"Mic2", "MIC2",
"LineInA", "INA1",
"LineInA", "INA2",
"LineInB", "INB1",
"LineInB", "INB2";
status = "okay";
};
[...]
&asrc0 {
fsl,asrc-rate = <48000>;
};
Audio codec (I2C3 slave)
&i2c3 {
[...]
max98089: codec@10 {
compatible = "maxim,max98089";
reg = <0x10>;
clocks = <&mclkout1_lpcg 0>;
clock-names = "mclk";
power-domains = <&pd IMX_SC_R_MCLK_OUT_1>;
vcc-supply = <®_3v3_audio>;
dvdd-supply = <®_1v8_ext>;
assigned-clocks = <&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_PLL>,
<&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_SLV_BUS>,
<&clk IMX_SC_R_AUDIO_PLL_0 IMX_SC_PM_CLK_MST_BUS>,
<&mclkout1_lpcg 0>;
assigned-clock-rates = <786432000>, <49152000>, <12288000>, <12288000>;
status = "okay";
};
[...]
};
&max98089 {
status = "okay";
};
Using 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