Arm linux uses alsa to drive and use usb audio devices
one。 Background:
The kernel version of arm linux is 3.13.0
two。 Preparatory work
Add alsa drivers to the kernel, that is, add the following options when compiling the kernel:
Then you can recompile the kernel.
three。 Cross-compile alsa-lib and alsa-utils (alsa-utils is a series of audio device control tools, and alsa-lib is the library that alsa-utils depends on, so compile alsa-lib first)
3.1 Cross-compile alsa-lib
3.2 Cross-compile alsa-utils
four。 Copy all the three compiled libraries and tools to the arm development board (the author usually directly compresses the compiled libraries and then copies them to the development board to decompress them, so as to avoid the situation that soft links cannot be copied directly)
five。 Use the tools in alsa-utils for all kinds of operations
5.1 recording:
Arecord-D "plughw:0,0" demo.wmv
5.2 play:
Aplay-D "plughw:0,0" demo.wmv
5.3 obtain control information:
Amixer controls
The output information is as follows:
Numid=3,iface=MIXER,name='Master Mode Switch'numid=29,iface=MIXER,name='Master Mux'numid=4,iface=MIXER,name='Master Quality Switch'numid=2,iface=MIXER,name='Master Switch'numid=1,iface=MIXER,name='Master Volume'numid=7,iface=MIXER,name='PCM Mode Switch'numid=6,iface=MIXER,name='PCM Switch'numid=5,iface=MIXER,name='PCM Volume'numid=9,iface=MIXER,name='Mic Switch'numid=8,iface=MIXER,name='Mic Volume'
5.4 get the volume when recording
The message "numid=8,iface=MIXER,name='Mic Volume'" can be obtained from 5.3. you can know from Mic Volume that it is the volume of Mic.
Amixer cget numid=8,iface=MIXER,name='Mic Volume'
5.4 set the volume for recording
Amixer cset numid=8,iface=MIXER,name='Mic Volume' 255
Six: points for attention:
If you copy the tools in the compiled alsa-utils to a storage device in fat32 format, note that fat32 does not support soft links. In this case, you need to directly copy an aplay and change the name to arecord:
Cp aplay arecord
Summary
The above is the editor to introduce to you the use of arm linux alsa driver and the use of usb audio equipment, I hope to help you!
