Zybo Z7-20 Audio Software Design Memorandum

This is the Software Designing (Petalinux) part of the Zybo Z7-20 audio system project. Appreciated Yuhei Horibe’s reference literature for Zedboard implementation and many of the Q&A for Zybo+I2S+PL300 DMA on “ADI Engineer Zone”.

The tool environments and preparation

Before starting this project, I have confirmed the Petalinux boot on the Zybo Z7-20 Rev. B board with following the tool environments as a preparation.

OS: Ubuntu 18.04 LTS on VirtualMachine 6.1 on MacBook Pro
HW: Xilinx Vivado/Vitis 2020.2
SW: Petalinux 2020.2

Download “sstate-cash-arm” from Xilinx

To speed up the Yocto LINUX building with sstate-cash.

% tar xf ~/Downloads/sstate_arm_2020.2.tar.gz -C /tools/petalinux

Configure the Petalinux

% petalinux-create --type project --template zynq --name Zybo
% cd Zybo
% petalinux-config --get-hw-description ../project_1/<file name>.xsa

Enable SD card as the root file system

Select EXT4 as the “Rootfs” on the configuration menu.

Set “Local sstate feed”

Add “Pre-mirror URL”

Disable “Network sstate feed”

1This is a kind of bug since the URL no more existed.

% petalinux-config -c kernel

Add the following additional kernel modules by click “y” on the menu.

Device Driver

Device Drivers -> Sound card support -> Advanced Linux Sound Architecture -> ALSA for SoC audio support -> ASoCo simple sound card support

ADI SSM2602-I2C CODEC driver

Device Drivers -> Sound card support -> Advanced Linux Sound Architecture -> ALSA for SoC audio support -> CODEC drivers -> Analog Devices SSM2602 CODEC — I2C

Then “<Save>” and then “<Exit>”.

% cd components/yocto/workspace/sources/linux-xlnx/oe-local-files
% cat devtool-fragment.cfg
CONFIG_SND_SOC_SSM2602=y
CONFIG_SND_SOC_SSM2602_I2C=y
CONFIG_SND_SIMPLE_CARD_UTILS=y
CONFIG_SND_SIMPLE_CARD=y

Userland

% petalinux-config -c rootfs

Filesystem Packages-> console -> utils -> alsa-tuils

Filesystem Packages-> base -> i2c-tuils

Edit the device-tree file

Edit project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi as following;

/include/ "system-conf.dtsi"
/ {
 // https://www.kernel.org/doc/Documentation/devicetree/bindings/sound/simple-card.txt
sound { // sound/soc/generic/simple-card.c
  compatible = "simple-audio-card";
  simple-audio-card,name    = "Zybo-Sound-Card";
  simple-audio-card,format  = "i2s";
     simple-audio-card,bitclock-master = <&cpu_dai>;
     simple-audio-card,frame-master    = <&cpu_dai>;
cpu_dai: simple-audio-card,cpu {
   sound-dai = <&axi_i2s_adi_0>;
   clocks = <&misc_clk_0>;  // 12288000
  };
codec_dai: simple-audio-card,codec {
   sound-dai = <&ssm2603>;
   clocks = <&misc_clk_0>;  // 12288000
  };
 };
};
&axi_i2s_adi_0 {
 #sound-dai-cells = <0>;    // only single DAI
 clock-names = "ref", "axi";
 clocks = <&misc_clk_0>, <&clkc 15>;
 compatible = "adi,axi-i2s-1.00.a";
 dmas = <&dmac_s 0 &dmac_s 1>;
 dma-names = "tx", "rx";
};
&i2c0 {
 status = "okay";
 ssm2603: ssm2603@1a {
  #sound-dai-cells = <0>;   // only single DAI
     compatible = "adi,ssm2603";
     reg = <0x1a>;
    };
};

• You may change “clocks” and “dmas” names properly.

Edit ssm2602.c

components/yocto/workspace/sources/linux-xlnx/sound/soc/codec/ssm2602.c

FPGA can only generate 48KHz (12.288MHz/64/4）format, so Codec device driver should declare it to inform LINUX, then ALSA will insert SRC properly in case of 44.1KHz series sampling playback.

496,499c496,499
< #define SSM2602_RATES (SNDRV_PCM_RATE_8000 | \
<   SNDRV_PCM_RATE_16000 | \
<   SNDRV_PCM_RATE_32000 | \
<   SNDRV_PCM_RATE_48000 | \
---
> #define SSM2602_RATES (SNDRV_PCM_RATE_8000 | SNDRV_PCM_RATE_11025 |\
>   SNDRV_PCM_RATE_16000 | SNDRV_PCM_RATE_22050 |\
>   SNDRV_PCM_RATE_32000 | SNDRV_PCM_RATE_44100 |\
>   SNDRV_PCM_RATE_48000 | SNDRV_PCM_RATE_88200 |\

Build the Linux and BOOT.BIN

% petalinlsux-build 
% petalinux-package --boot --force --fsbl images/linux/zynq_fsbl.elf --fpga images/linux/system.bit --u-boot

Copy image and rootfs to SD-card

% cd images/linux
% sudo cp BOOT.BIN boot.scr image.ub /media/sdcard/boot/
% sudo tar xf rootfs.tar.gz -C /media/sdcard/root/
% sudo sync 

Boot LINUX and login

We could confirm axi_i2s_adi mapped to ssm2602-hifi OK.

I2C communication can R/W SSM2603.

Now we can play the WAV file with “aplay” or “speaker-test” command and ALSA may insert proper Rate Converter as following;

root@Zybo:~# aplay -v FreeVocal12_44k.wav 
Playing WAVE ‘FreeVocal12_44k.wav’ : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo
Plug PCM: Rate conversion PCM (48000, sformat=S32_LE)
Converter: linear-interpolation
Protocol version: 10002
Its setup is:
 stream : PLAYBACK
 access : RW_INTERLEAVED
 format : S16_LE
 subformat : STD
 channels : 2
 rate : 44100
 exact rate : 44100 (44100/1)
 msbits : 16
Slave: Hardware PCM card 0 ‘Zybo-Sound-Card’ device 0 subdevice 0
Its setup is:
 stream : PLAYBACK
 access : MMAP_INTERLEAVED
 format : S32_LE
 subformat : STD
 channels : 2
 rate : 48000
 exact rate : 48000 (96000/2)
 msbits : 32
root@Zybo:~# aplay -v FreeVocal12_48k.wav 
Playing WAVE 'FreeVocal12_48k.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
Plug PCM: Linear conversion PCM (S32_LE)
Its setup is:
  stream       : PLAYBACK
  access       : RW_INTERLEAVED
  format       : S16_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 16
Slave: Hardware PCM card 0 'Zybo-Sound-Card' device 0 subdevice 0
Its setup is:
  stream       : PLAYBACK
  access       : MMAP_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (96000/2)
  msbits       : 32

One problem is that SSM2603 initialization has a problem and generating noise until to communicate first I2C command from the user application such as “aplay -f S32_LE” etc…

Continue to the next memorandum.

Reference Link

HDL AXI I2S Linux Driver

https://www.kernel.org/doc/Documentation/devicetree/bindings/sound/simple-card.txt

Petalinux build fails

Zedboard PL audio

Linux device driver for Zedboard audio (1/2)

Linux device driver for Zedboard audio (2/2)