topic Re: IMX8M Plus - digital PDM MIC connection in i.MX Processors

IMX8M Plus - digital PDM MIC connection

haryanl — Tue, 09 Jan 2024 09:06:38 GMT

Dear Team,

Currently we only use 1 PDM MIC SPH0655LM4H-1, but cannot record.
Is it mandatory to connect to PDM_BIT_STREAM0 first?
we are connecting to PDM_BIT_STREAM1 pin.

If we have to connect to PDM_BIT_STREAM0 first, is there any way to fix it without repairing the hardware?

Thanks in advance

Kind regards,

Re: IMX8M Plus - digital PDM MIC connection

JorgeCas — Tue, 09 Jan 2024 20:05:49 GMT

Hello, I hope you are doing well.

It should not be an issue use PDM_BIT_STREAM1 and not PDM_BIT_STREAM0 first.

Is it recognized correctly?

Do you have data signals from the MIC?

Best regards.

Re: IMX8M Plus - digital PDM MIC connection

haryanl — Wed, 10 Jan 2024 06:42:03 GMT

Hi JorgeCas,

I use the following command:
"arecord -Dsysdefault:CARD=imxaudiomicfil -f S32_LE -d30 -r 48000 capture.wav -vvv"

When I connect the MIC to PDM_BIT_STREAM0, I can record, save the .wav file, and replay it.

but when I connect to PDM_BIT_STREAM1, the error "Max peak (6000 samples): 0x7fffe000 #################### 99%" appears continuously. It appears that audio data is not being recorded
Is there any way to fix it?

Below is the log in 2 cases:

1. connect to PDM_BIT_STREAM0:
root@imx8mp-lpddr4-evk:~# arecord -Dsysdefault:CARD=imxaudiomicfil -f S32_LE -d30 -r 48000 capture.wav -vvv
Recording WAVE 'capture.wav' : Signed 32 bit Little Endian, Rate 48000 Hz, Mono
Plug PCM: Hardware PCM card 3 'imx-audio-micfil' device 0 subdevice 0
Its setup is:
stream       : CAPTURE
access       : RW_INTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 1
rate         : 48000
exact rate   : 48000 (48000/1)
msbits       : 32
buffer_size : 24000
period_size : 6000
period_time : 125000
tstamp_mode : NONE
tstamp_type : MONOTONIC
period_step : 1
avail_min    : 6000
period_event : 0
start_threshold : 1
stop_threshold   : 24000
silence_threshold: 0
silence_size : 0
boundary     : 6755399441055744000
appl_ptr     : 0
hw_ptr       : 0
Max peak (6000 samples): 0x7fffe600 #################### 99%
Max peak (6000 samples): 0x0029a000 #                    0%
Max peak (6000 samples): 0x0035c600 #                    0%
Max peak (6000 samples): 0x00272a00 #                    0%
Max peak (6000 samples): 0x001ccf00 #                    0%
Max peak (6000 samples): 0x00118700 #                    0%
Max peak (6000 samples): 0x00151100 #                    0%
Max peak (6000 samples): 0x0016c000 #                    0%
Max peak (6000 samples): 0x00179b00 #                    0%
Max peak (6000 samples): 0x00240e00 #                    0%
Max peak (6000 samples): 0x004b4b00 #                    0%
Max peak (6000 samples): 0x01696100 #                    1%
Max peak (6000 samples): 0x01db8600 #                    1%
Max peak (6000 samples): 0x02843700 #                    1%
Max peak (6000 samples): 0x0f26a000 ###                  11%
Max peak (6000 samples): 0x5c5a1200 ###############      72%
Max peak (6000 samples): 0x03f88f00 #                    3%
Max peak (6000 samples): 0x0faada00 ###                  12%
Max peak (6000 samples): 0x7e059d00 #################### 98%
Max peak (6000 samples): 0x201da200 ######               25%
Max peak (6000 samples): 0x74122700 ################### 90%
Max peak (6000 samples): 0x7ca0a200 #################### 97%
Max peak (6000 samples): 0x7bbdb700 #################### 96%
Max peak (6000 samples): 0x75d63500 ################### 92%
Max peak (6000 samples): 0x7c29a300 #################### 97%
Max peak (6000 samples): 0x7f1c0d00 #################### 99%
Max peak (6000 samples): 0x7b097800 #################### 96%
Max peak (6000 samples): 0x03dff200 #                    3%
Max peak (6000 samples): 0x02bd9c00 #                    2%
Max peak (6000 samples): 0x0222ad00 #                    1%
Max peak (6000 samples): 0x01827100 #                    1%
Max peak (6000 samples): 0x00ac8d00 #                    0%
Max peak (6000 samples): 0x001a8000 #                    0%
^CAborted by signal Interrupt...
Max peak (6000 samples): 0x001cd700 #                    0%
2. Connect to PDM_BIT_STREAM1:
root@imx8mp-lpddr4-evk:~# arecord -Dsysdefault:CARD=imxaudiomicfil -f S32_LE -d30 -r 48000 capture.wav -vvv
Recording WAVE 'capture.wav' : Signed 32 bit Little Endian, Rate 48000 Hz, Mono
Plug PCM: Hardware PCM card 2 'imx-audio-micfil' device 0 subdevice 0
Its setup is:
stream       : CAPTURE
access       : RW_INTERLEAVED
format       : S32_LE
subformat    : STD
channels     : 1
rate         : 48000
exact rate   : 48000 (48000/1)
msbits       : 32
buffer_size : 24000
period_size : 6000
period_time : 125000
tstamp_mode : NONE
tstamp_type : MONOTONIC
period_step : 1
avail_min    : 6000
period_event : 0
start_threshold : 1
stop_threshold   : 24000
silence_threshold: 0
silence_size : 0
boundary     : 6755399441055744000
appl_ptr     : 0
hw_ptr       : 0
Max peak (6000 samples): 0x7fffe500 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%
Max peak (6000 samples): 0x7fffe000 #################### 99%

Re: IMX8M Plus - digital PDM MIC connection

JorgeCas — Wed, 10 Jan 2024 18:37:27 GMT

Hello,

I tried to replicate the issue, but I was not able to do it.

Maybe you could try to use plughw, such as:

arecord -D plughw:1,0 -f S32_LE -d10 -r 48000 capture.wav -vvv

Also, could you please try to with a different quality with amixer, for example:

root@imx8mpevk:~# amixer -c 1 cset name='MICFIL Quality Select' 0 numid=9,iface=MIXER,name='MICFIL Quality Select' ; type=ENUMERATED,access=rw------,values=1,items=6 ; Item #0 'High' ; Item #1 'Medium' ; Item #2 'Low' ; Item #3 'VLow0' ; Item #4 'Vlow1' ; Item #5 'Vlow2' : values=0

Best regards.

Re: IMX8M Plus - digital PDM MIC connection

haryanl — Thu, 11 Jan 2024 08:06:57 GMT

Hi JorgeCas,

I tried your command, but errors appear

root@imx8mp-lpddr4-evk:~# amixer -c 1 cset name='MICFIL Quality Select' 0 amixer: Cannot find the given element from control sysdefault:1

root@imx8mp-lpddr4-evk:~# arecord -D plughw:1,0 -f S32_LE -d10 -r 48000 capture.wav -vvv arecord: main:831: audio open error: No such file or directory

I then tried changing the command as follows:

root@imx8mp-lpddr4-evk:~# amixer -Dsysdefault:CARD=imxaudiomicfil cset name='MICFIL Quality Select' 0 numid=9,iface=MIXER,name='MICFIL Quality Select' ; type=ENUMERATED,access=rw------,values=1,items=8 ; Item #0 'Medium' ; Item #1 'High' ; Item #2 'N/A' ; Item #3 'N/A' ; Item #4 'VLow2' ; Item #5 'VLow1' ; Item #6 'VLow0' ; Item #7 'Low' : values=0

root@imx8mp-lpddr4-evk:~# arecord -Dsysdefault:imxaudiomicfil -f S32_LE -d10 -r 48000 capture.wav -vvv Recording WAVE 'capture.wav' : Signed 32 bit Little Endian, Rate 48000 Hz, Mono Plug PCM: Hardware PCM card 2 'imx-audio-micfil' device 0 subdevice 0 Its setup is: stream : CAPTURE access : RW_INTERLEAVED format : S32_LE subformat : STD channels : 1 rate : 48000 exact rate : 48000 (48000/1) msbits : 32 buffer_size : 24000 period_size : 6000 period_time : 125000 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 6000 period_event : 0 start_threshold : 1 stop_threshold : 24000 silence_threshold: 0 silence_size : 0 boundary : 6755399441055744000 appl_ptr : 0 hw_ptr : 0 Max peak (6000 samples): 0x00fe0900 # 0% Max peak (6000 samples): 0x00fe0900 # 0% Max peak (6000 samples): 0x00fe0900 # 0% ~~~( ellipsis)~~~~ Max peak (6000 samples): 0x00fe0900 # 0% Max peak (6000 samples): 0x00fe0900 # 0% Max peak (6000 samples): 0x00fe0900 # 0% root@imx8mp-lpddr4-evk:~#

When running record, it returns all 0%

Is there any way to fix it?
Best regards,

Re: IMX8M Plus - digital PDM MIC connection

JorgeCas — Thu, 11 Jan 2024 13:18:12 GMT

Hello,

Is sound card 1,0 of -Dplughw the same as imxaudiomicfil on your system? The -D plughw:1,0 of my example command corresponds to my list of sound cards and sub-devices detected, you should try with imxaudiomicfil as is showed on your command log of:

arecord -l

The same applies to amixer -c <your mic>

Best regards.

Re: IMX8M Plus - digital PDM MIC connection

haryanl — Tue, 16 Jan 2024 10:09:04 GMT

Hello JorgeCas,
My Software team is trying to debug it
Thank you for your support
I would like to temporarily close this topic

Best regards,