DESK-MX8M-L/Peripherals/Audio
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Contents
Peripheral Audio[edit | edit source]
Access to the audio interface is provided by ALSA (Advanced Linux Sound Architecture), which consists in a kernel driver and a users space library for application developers. A set of standard tools (alsa-utils) can be used for simple management of the audio codec.
Device tree configuration[edit | edit source]
MITO 8M Mini[edit | edit source]
Here below an example of device tree configuration used on standard DAVE's kit for MITO 8M Mini:
From imx8mm-mito8mmini.dtsi it is possible to find the Serial Audio Interface configuration:
...
&sai2 {
#sound-dai-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai2>;
assigned-clocks = <&clk IMX8MM_CLK_SAI2>;
assigned-clock-parents = <&clk IMX8MM_AUDIO_PLL1_OUT>;
assigned-clock-rates = <24576000>;
status = "disabled";
};
...
&iomuxc {
...
pinctrl_sai2: sai2grp {
fsl,pins = <
MX8MM_IOMUXC_SAI2_MCLK_SAI2_MCLK 0xd6
MX8MM_IOMUXC_SAI2_TXFS_SAI2_TX_SYNC 0xd6
MX8MM_IOMUXC_SAI2_TXC_SAI2_TX_BCLK 0xd6
MX8MM_IOMUXC_SAI2_TXD0_SAI2_TX_DATA0 0xd6
MX8MM_IOMUXC_SAI2_RXFS_SAI2_RX_SYNC 0xd6
MX8MM_IOMUXC_SAI2_RXC_SAI2_RX_BCLK 0xd6
MX8MM_IOMUXC_SAI2_RXD0_SAI2_RX_DATA0 0xd6
>;
};
...
From imx8mm-mito8mmini-sbcx.dts it is possible to find the codec SSI interface configuration:
...
...
sound {
compatible = "simple-audio-card";
simple-audio-card,format = "i2s";
simple-audio-card,name = "SBCX_TLV320";
simple-audio-card,bitclock-master = <&cpu_dai>;
simple-audio-card,frame-master = <&cpu_dai>;
simple-audio-card,widgets =
"Headphone", "Headphone Jack",
"Line", "Line In",
"Microphone", "Mic Jack";
simple-audio-card,routing =
"Speaker", "SPK",
"Headphone Jack", "HPL",
"Headphone Jack", "HPR",
"MIC1LP", "Line In",
"MIC1LM", "Line In",
"MIC1RP", "Mic Jack",
"Mic Jack", "MICBIAS";
simple-audio-card,mclk-fs = <256>;
cpu_dai: simple-audio-card,cpu {
sound-dai = <&sai2>;
};
codec_dai: simple-audio-card,codec {
sound-dai = <&codec>;
system-clock-frequency = <12288000>;
};
};
...
&sai2 {
pinctrl-names = "default";
status = "okay";
};
...
&iomuxc {
...
pinctrl_codec_en: codecen {
fsl,pins = <
MX8MM_IOMUXC_SAI3_RXFS_GPIO4_IO28 0x19
>;
};
...
...
Accessing the peripheral[edit | edit source]
Linux messages at boot time[edit | edit source]
To list the audio sound cards just use the aplay utility:
root@desk-mx8mm:~# aplay -l **** List of PLAYBACK Hardware Devices **** card 0: SBCXTLV320 [SBCX_TLV320], device 0: 30020000.sai-tlv320aic31xx-hifi tlv320aic31xx-hifi-0 [30020000.sai-tlv320aic31xx-hifi tlv320aic31xx-hifi-0] Subdevices: 1/1 Subdevice #0: subdevice #0 root@desk-mx8mm:~#
Usage alsa-utils[edit | edit source]
In order to unmute the speaker the amixer utility can be used.
root@desk-mx8mm:~# amixer sset 'Speaker',0 on Simple mixer control 'Speaker',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] root@desk-mx8mm:~# amixer sset 'Speaker Analog',0 108 Simple mixer control 'Speaker Analog',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 127 Mono: Playback 108 [85%] [-9.50dB] root@desk-mx8mm:~# amixer sset 'Speaker Driver',0 on Simple mixer control 'Speaker Driver',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback 0 - 3 Mono: Playback 0 [0%] [6.00dB] [on] root@desk-mx8mm:~# amixer sset 'Speaker Driver',0 2 Simple mixer control 'Speaker Driver',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback 0 - 3 Mono: Playback 2 [67%] [18.00dB] [on] root@desk-mx8mm:~# amixer sset 'DAC',0 155 Simple mixer control 'DAC',0 Capabilities: pvolume Playback channels: Front Left - Front Right Limits: Playback 0 - 175 Mono: Front Left: Playback 155 [89%] [14.00dB] Front Right: Playback 155 [89%] [14.00dB] root@desk-mx8mm:~# amixer sset 'Output Left From Left DAC',0 on Simple mixer control 'Output Left From Left DAC',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on] root@desk-mx8mm:~#
To perform a sound, execute the command:
root@desk-mx8mm:~# speaker-test -c 1 -t wav speaker-test 1.2.6 Playback device is default Stream parameters are 48000Hz, S16_LE, 1 channels WAV file(s) Rate set to 48000Hz (requested 48000Hz) Buffer size range from 3840 to 5760 Period size range from 1920 to 1920 Using max buffer size 5760 Periods = 4 was set period_size = 1920 was set buffer_size = 5760 0 - Front Left ...
Additional information[edit | edit source]
Information about alsa-utils can be found on ALSA project wiki pages
