DESK-MX8M-L/Peripherals/Audio
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| ID# | Issue Date | Notes | |
| 24/02/2023 | DESK-MX8M-L 2.0.0 release | ||
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.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 = <&codec_dai>;
simple-audio-card,frame-master = <&codec_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,cpu {
sound-dai = <&sai2>;
};
codec_dai: simple-audio-card,codec {
sound-dai = <&codec>;
system-clock-frequency = <24000000>;
};
};
...
...
&sai2 {
#sound-dai-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai2>;
pinctrl-1 = <&pinctrl_codec_en>;
clocks = <&clk IMX8MM_CLK_SAI2_ROOT>;
assigned-clocks = <&clk IMX8MM_CLK_SAI2>;
assigned-clock-parents = <&clk IMX8MM_AUDIO_PLL1_OUT>;
assigned-clock-rates = <24576000>;
status = "okay";
};
...
...
&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
>;
};
...
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]
... ... [ 5.259739] debugfs: Directory '30020000.sai' with parent 'SBCX_TLV320' already present! [ 5.267980] asoc-simple-card sound: tlv320aic31xx-hifi <-> 30020000.sai mapping ok ... ... [ 5.454902] ALSA device list: [ 5.454906] #0: SBCX_TLV320
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 [] 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" on Simple mixer control 'Speaker',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on]
root@desk-mx8mm:~# amixer sset "Speaker Analog" 100 Simple mixer control 'Speaker Analog',0 Capabilities: pvolume pvolume-joined Playback channels: Mono Limits: Playback 0 - 127 Mono: Playback 100 [79%] [-13.50dB]
root@desk-mx8mm:~# amixer sset "Speaker Driver" on 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" 100 Simple mixer control 'DAC',0 Capabilities: pvolume Playback channels: Front Left - Front Right Limits: Playback 0 - 175 Mono: Front Left: Playback 100 [57%] [-13.50dB] Front Right: Playback 100 [57%] [-13.50dB]
root@desk-mx8mm:~# amixer sset "Output Left From Left DAC" on Simple mixer control 'Output Left From Left DAC',0 Capabilities: pswitch pswitch-joined Playback channels: Mono Mono: Playback [on]
To perform a sound, execute the command:
root@desk-mx8mm:~# aplay sample_22_frames.mp3 Playing raw data 'sample_22_frames.mp3' : Unsigned 8 bit, Rate 8000 Hz, Mono
Additional information[edit | edit source]
Information about alsa-utils can be found on ALSA project wiki pages
