ROCK PI S音频开发（一）系统准备-Toy模板网

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1、连接WIFI

sudo nmcli r wifi on
sudo nmcli dev wifi
sudo nmcli dev wifi connect "SSID" password "PASSWORD"

2、更新源

sudo apt-get update
sudo apt-get install git wget
export DISTRO=focal-stable
wget -O - apt.radxa.com/$DISTRO/public.key | sudo apt-key add -
sudo apt-get update

3、安装相关编译器

sudo apt-get install gcc-aarch64-linux-gnu build-essential device-tree-compiler libncurses5 libncurses5-dev make cmake

4、安装基础音频软件

sudo apt-get install alsa-utils jackd2 jackmeter mplayer

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接下来做一些基本的测试

1、jackd服务

jackd -dalsa -dhw:1 -r44100&

查看端口

jack_lsp

2、要使用高品质音频，需采用I2S的方式连接外部解码器，通过编译设备树将相应IO配置为I2S模式

2.1 反编译DTB

dtc -I dtb -O dts -o xx.dtb xxx.dts

即把/boot/dtbs/4.4.143-65-rockchip-g58431d38f8f3/rockchip/rk3308-rock-pi-s.dtb反编译为dts，然后对该文件进行编辑

dtc -I dtb -O dts -o /boot/dtbs/4.4.143-65-rockchip-g58431d38f8f3/rockchip/rk3308-rock-pi-s.dtb rk3308-rock-pi-s.dts

运行上述命令后，将在当前目录下生成rk3308-rock-pi-s.dts，接下来对该文件的以下片段进行修改，不使用rock pi s自带的音频解码器，并将IO配置为I2S模式。

2.2 I2S slave模式的设备树

	i2s_8ch_0: i2s@ff300000 {
		compatible = "rockchip,rk3308-i2s-tdm";
		reg = <0x00 0xff300000 0x00 0x1000>;
		interrupts = <0x00 0x30 0x04>;
		clocks = <0x02 0x4c 0x02 0x4e 0x02 0xa4 0x02 0x6e 0x02 0x6f 0x02 0x03 0x02 0x04>;
		clock-names = "mclk_tx\0mclk_rx\0hclk\0mclk_tx_src\0mclk_rx_src\0mclk_root0\0mclk_root1";
		dmas = <0x25 0x00 0x25 0x01>;
		dma-names = "tx\0rx";
		resets = <0x02 0x89 0x02 0x8a>;
		reset-names = "tx-m\0rx-m";
		rockchip,cru = <0x02>;
		rockchip,grf = <0x4b>;
		rockchip,mclk-calibrate;
		pinctrl-names = "default";
		pinctrl-0 = <0x4e 0x4f 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5a>;		
		rockchip,clk-trcm = <2>;
		#sound-dai-cells = <0>;
		status = "okay";
		phandle = <0xbe>;
	};

	I2S_sound {
		status = "okay";
		compatible = "simple-audio-card";
		simple-audio-card,format = "i2s";
		simple-audio-card,name = "dummy-card";
		simple-audio-card,mclk-fs = <256>;
		simple-audio-card,bitclock-master = <&master>;
		simple-audio-card,frame-master = <&master>;
		simple-audio-card,cpu {
			sound-dai = <&i2s_8ch_0>;
		};
		master:simple-audio-card,codec {
			sound-dai = <&dummy_codec>;
		};
	};
	
 	dummy_codec: dummy-codec {
         status = "okay";
         compatible = "rockchip,dummy-codec";
		 //clocks = <0x02 0x6f>;
		 //clock-names = "mclk";
         #sound-dai-cells = <0>;
    };
	

	acodec-sound {
		compatible = "rockchip,multicodecs-card";
		rockchip,card-name = "rockchip,rk3308-acodec";
		rockchip,multicodecs-card,format = "i2s";
		rockchip,mclk-fs = <0x100>;
		rockchip,cpu = <&i2s_8ch_0>;
		rockchip,codec = <0x8b>;
		status = "disabled";
		phandle = <0x13d>;		
	};

2.3 I2S master模式的设备树

	i2s_8ch_0: i2s@ff300000 {
		compatible = "rockchip,rk3308-i2s-tdm";
		reg = <0x00 0xff300000 0x00 0x1000>;
		interrupts = <0x00 0x30 0x04>;
		clocks = <0x02 0x4c 0x02 0x4e 0x02 0xa4 0x02 0x6e 0x02 0x6f 0x02 0x03 0x02 0x04>;
		clock-names = "mclk_tx\0mclk_rx\0hclk\0mclk_tx_src\0mclk_rx_src\0mclk_root0\0mclk_root1";
		dmas = <0x25 0x00 0x25 0x01>;
		dma-names = "tx\0rx";
		resets = <0x02 0x89 0x02 0x8a>;
		reset-names = "tx-m\0rx-m";
		rockchip,cru = <0x02>;
		rockchip,grf = <0x4b>;
		rockchip,mclk-calibrate;
		pinctrl-names = "default";
		pinctrl-0 = <0x4e 0x4f 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5a>;		
		rockchip,clk-trcm = <2>;
		#sound-dai-cells = <0>;
		status = "okay";
		phandle = <0xbe>;
	};

	I2S_sound {
		status = "okay";
		compatible = "simple-audio-card";
		simple-audio-card,format = "i2s";
		simple-audio-card,name = "dummy-card";
		simple-audio-card,mclk-fs = <256>;
		simple-audio-card,bitclock-master = <&i2s_8ch_0>;
		simple-audio-card,frame-master = <&i2s_8ch_0>;
		simple-audio-card,cpu {
			sound-dai = <&i2s_8ch_0>;
		};
		master:simple-audio-card,codec {
			sound-dai = <&dummy_codec>;
		};
	};
	
 	dummy_codec: dummy-codec {
         status = "okay";
         compatible = "rockchip,dummy-codec";
		 //clocks = <0x02 0x6f>;
		 //clock-names = "mclk";
		 //pinctrl-names = "default";
		 //pinctrl-0 = <0x5a>;
         #sound-dai-cells = <0>;
    };
	

	acodec-sound {
		compatible = "rockchip,multicodecs-card";
		rockchip,card-name = "rockchip,rk3308-acodec";
		rockchip,multicodecs-card,format = "i2s";
		rockchip,mclk-fs = <0x100>;
		rockchip,cpu = <&i2s_8ch_0>;
		rockchip,codec = <0x8b>;
		status = "disabled";
		phandle = <0x13d>;		
	};

3、编译修改完成的dts文件

sudo dtc -I dts -O dtb -f rk3308-rock-pi-s.dts -o /boot/dtbs/4.4.143-65-rockchip-g58431d38f8f3/rockchip/rk3308-rock-pi-s.dtb

重启系统

sudo reboot

--------------------------------------------------------------------------------------------------------------------------------文章来源地址https://www.toymoban.com/news/detail-486390.html

如果使用I2S master模式，ROCK PI S的DACLRCK、DACBCK针脚为输出，那么在启动jacd服务后，这两个针脚应将产生到对应的频率

jackd -dalsa -dhw:1 -r44100

如果使用I2S slave模式，LRCK、BCK针脚由外部时钟提供，如果外部时钟不存在，jackd服务将不能正常启动。

接下来会产生一个问题，在I2S master模式下，只产生BCK和LRCK时钟，没有MCLK时钟，可能有些外部解码器需要提供MCLK时钟，这个问题还没搞清楚怎么办，不过有一种硬件的解决方案是使用锁相环倍频电路，不过此电路的缺点是最高支持48k采样率。

锁相环倍频电路

ROCK PI S音频开发（一）系统准备

假如CLK-IN输入的是LRCK时钟，74HC4046的3脚就与74HC4040的256分频连接，此时CLK-OUT输出就是11.2896M，或者CLK-IN输入的是BCK时钟，74HC4046的3脚就与74HC4040的4分频连接，此时CLK-OUT输出也是11.2896M。CLK-OUT就是通过倍频生成的MCLK时钟。

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如果使用I2S SLAVE模式就简单了，使用有源晶振直接分频即可，参照以下电路即可得到MCLK,BCK,LRCK三个时钟信号

ROCK PI S音频开发（一）系统准备