Hi, there are several questions confusing me. First, although I use the CTAG img ctag_bone_debian_v0.1.2.img.xz, however, I can not use debian to login, instead, I can use root@192.168.7.2， which shows it almost the same as Bela img. Is there anything wrong?

hmm, if you bought the beaglebone from us, you will have a Bela image on the eMMC (the internal memory of the Beaglebone). You should get rid of that:
- boot without SD card
- run

ssh root@192.168.7.2 dd if=/dev/zero of=/dev/mmcblk1 bs=1M count=50

- boot with SD card
- run

ssh debian@beaglebone.local

(use password temppwd)

    giuliomoro Oh. Thanks. It works now. Then how to build up a ALSA projects on the board now?

      You will have to follow tutorials for regular Linux/ALSA applications. @henrix can hopefully provide more assistance on that.

        giuliomoro There are some errors when I use scripts
        sudo ./load-ctag-beast-16ch-drivers.sh

          giuliomoro
          ./load-ctag-beast-16ch-drivers.sh: line 2: echo: write error: Device or resource busy
          ./load-ctag-beast-16ch-drivers.sh: line 9: echo: write error: File exists

            Hi @sunwell ,

            Can you please verify that there are no other audio card drivers loaded (via. aplay -l)?
            The CTAG image shouldn't load any audio drivers by default.
            Can you please also check your kernel version (uname -r)?

              henrix Thanks. I have checked everything and there is no error now. However, I have come across another problem. I tried to use 96kHz or even 192kHz to record 8 channels simultaneously by arecord command, however it can not work. When I use 48kHz to sample, it works well. Do you have any ideas? Thanks!

                With 16 channels the maximum sample rate is 48 kHz due to the fixed master clock generated by a 24.576MHz crystal. Hence, if you want to use 96 kHz sample rate, you have to load the 8 channel face overlay.

                  henrix I use the input instead of the output. So there are 4 inputs of each FACE board. What is the sampling rate for input microphones? Thanks!

                    henrix What is the maximum sampling rate for the input microphones?

                      The sample rate is the same as for the DACs due to hardware restrictions.
                      Hence, if you want to use 96kHz sample rate, you have to load the FACE driver as well.

                        henrix Thanks. Thus the max sampling rate for microphones in BEAST system is 48kHZ and that for FACE microphones is 96kHZ. There is no way to reach up to 192kHz of input?

                          @sunwell Right, with the BEAST overlay, a max. sample rate of 48 kHz is possible. With FACE overlay, 96 kHz. 192 kHz is supported by hardware as well if you enable 4 IO channels only. However, currently there are only overlays for 8 (FACE) and 16 channels (BEAST). If you need 192 kHz, I could create a 4 IO channels overlay.

                            henrix Thanks. I hope to use 192kHz. Could you create such a overlay?

                              henrix Another problem is what is the delay between each microphone input? It seems that they are not simultaneous strictly.

                                @sunwell Ok, I will create the overlay for 4 IOs with 192 KHz today. The IOs are all sample accurate. Thus, there shouldn't be a delay.

                                @sunwell Here is an overlay with 4 channels enabled only. The driver should compute the max. sample rate automatically. I upped the binary in my GDrive (will push it to GitHub after evaluation):

                                Copy the .dtbo to /lib/firmware and change the driver in a CTAG loader script to the according device tree overlay (i.e. BB-CTAG-SW-8CH to BB-CTAG-SW-4CH) and execute the script. Verify the correct driver is loaded via aplay -l (it should list CTAG Multi-Audio IO 4CH).