本文基于触觉智能RK3506核心板/开发板，介绍DSM音频功能使用攻略。
DSM简介
DSM
DSM（Delta-Sigma Modulation，德尔塔-西格玛调制）音频原理，DSM 的核心是一种过采样噪声整形技术，它的目标不是一次性精确地记录每个采样点的幅度，而是通过极高的采样率来记录相邻采样点之间的变化（Delta, Δ），并将量化误差（噪声）推挤（Sigma, Σ, 意为求和与积累） 到人耳不敏感的高频区域，再通过数字滤波器将其滤除。
DSM应用
以ADC为例，负责将麦克风、乐器等模拟音频信号转换为数字信号，DSM 技术在此场景中解决了 “高精度与低成本” 的矛盾 —— 传统多位数 ADC（如 16 位、24 位）依赖复杂的模拟电路来保证精度，而 DSM ADC 通过 1 位量化器 + 过采样 / 噪声整形，用数字算法替代部分模拟电路成本，同时实现更高动态范围。像汽车音频：车载麦克风（用于语音助手、降噪通话）。汽车环境存在发动机、风噪等干扰，DSM 的噪声整形技术可将量化噪声推至人耳不敏感的高频段（>20kHz），提升语音信号的信噪比。
硬件连接参考
硬件修改
触觉智能RK3506开发板由于默认使用ES8388音频编解码芯片，需整改硬件，修改如下：空贴R183、R174，焊接R180、R178。
触觉智能RK3506开发板，相关底板详细资料请关注深圳触觉智能CDSN或 官方客服134 2385 6106，提供软硬件资料与Demo。
内核配置
打补丁
将触觉智能提供的RK3506网盘中，软件资料/Linux/patch/dsm路径下的文件替换<SDK_PATH>/kernel/sound/soc/codecs/下的文件。
DTS配置
相关配置如下，需要注意以下2点：
1.RK3506 sndcpu必须为sai3。
dsm_sound: dsm-sound {
status = "okay";
compatible = "simple-audio-card";
simple-audio-card,format = "i2s";
simple-audio-card,mclk-fs = ;
simple-audio-card,name = "rockchip,dsm-sound";
simple-audio-card,bitclock-master = ;
simple-audio-card,frame-master = ;
sndcpu: simple-audio-card,cpu {
sound-dai = ;
};
sndcodec: simple-audio-card,codec {
sound-dai = ;
};
};
&acdcdig_dsm {
status = "okay";
};
&sai3 {
status = "okay";
};
&audio_codec {
status = "okay";
};2.触觉智能RK3506开发板(EVB3506)的es8388声卡与DSM复用，所以配置DSM功能前需先关闭es8388相关配置。
es8388_sound: es8388-sound {
status = "disabled";
compatible = "rockchip,multicodecs-card";
rockchip,card-name = "rockchip-es8388";
spk-con-gpio = ;
rockchip,pre-power-on-delay-ms = ;
rockchip,post-power-down-delay-ms = ;
rockchip,format = "i2s";
rockchip,mclk-fs = ;
rockchip,cpu = ;
rockchip,codec = ;
rockchip,audio-routing =
"Headphone", "LOUT1",
"Headphone", "ROUT1",
"Speaker", "LOUT2",
"Speaker", "ROUT2",
"Headphone", "Headphone Power",
"Headphone", "Headphone Power",
"Speaker", "Speaker Power",
"Speaker", "Speaker Power",
"RINPUT1", "Main Mic",
"RINPUT2", "Main Mic",
"LINPUT1", "Headset Mic",
"LINPUT2", "Headset Mic";
pinctrl-names = "default";
pinctrl-0 = ;
};
&i2c0 {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = ;
es8388: es8388@11 {
status = "disabled";
#sound
-dai-cells = ;
compatible = "everest,es8388", "everest,es8323";
reg = ;
clocks = ;
clock-names = "mclk";
assigned-clocks = ;
assigned-clock-rates = ;
pinctrl-names = "default";
pinctrl-0 = ;
};
};播放音频测试方法
查看DSM声卡，命令如下：
root@rk3506-buildroot:/# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 1: rockchipdsmsoun [rockchip,dsm-sound], device 0: ff4a0000.sai-rk_dsm rk_dsm-0 [ff4a0000.sai-rk_dsm rk_dsm-0]
Subdevices: 1/1
Subdevice
#0
: subdevice
#0
root@rk3506-buildroot:/#配置功放芯片，将功放芯片开关脚拉高，命令如下：
root@rk3506-buildroot:/root# echo 14 > /sys/class/gpio/export
root@rk3506-buildroot:/root# echo out > /sys/class/gpio/gpio14/direction
root@rk3506-buildroot:/root# echo 255 > /sys/class/gpio/gpio14/value使用aplay播放音频，命令如下：
root@rk3506-buildroot:/# aplay -Dhw:1,0 1KHZ.wav
Playing WAVE '1KHZ.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo当播放1k频率音频文件，示波器抓取经过RC滤波前后的音频信号如下:
RC滤波前的信号为放大查看：
RC滤波后的音频信号查看：
