I am trying a Adafruit I2S 3W Stereo Speaker Bonnet for Raspberry Pi - Mini Kit, which is built around two MAX98357 (datasheet: adafruit, maxim), on a Raspberry Pi Zero W with Raspbian Stretch (upgraded yesterday).
The trouble is that I have "pops" when starting/changing tracks, even with the same audio rate. Their instructions to "fix" these add mostly redundant settings to the alsa configuration files /etc/asound.conf and ~/.asoundrc.
I currently only have asound.conf, like this:
$ cat /etc/asound.conf
pcm.speakerbonnet {
type hw card 0
}
pcm.dmixer {
type dmix
ipc_key 1024
ipc_perm 0666
slave {
pcm "speakerbonnet"
period_time 0
period_size 1024
buffer_size 8192
rate 44100
channels 2
}
}
ctl.dmixer {
type hw card 0
}
pcm.softvol {
type softvol
slave.pcm "dmixer"
control.name "PCM"
control.card 0
}
ctl.softvol {
type hw card 0
}
pcm.!default {
type plug
slave.pcm "softvol"
slave.pcm "dmixer"
}
softvol exists to be able to control volume globally (in software, wasting resolution), since the DAC does not have hardware control. But apparently some players also can do this themselves, so either should suffice.
Regarding the driver, their instructions add dtoverlay=hifiberry-dac to /boot/config.txt, but the Hifiberry DAC (obsolete) is based on a (single) different chip, the PCM5102.
pi@raspberry:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dac], device 0: HifiBerry DAC HiFi pcm5102a-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
Hifiberry list the configuration for their products at https://www.hifiberry.com/build/documentation/configuring-linux-3-18-x/.
I'd like to know what the differences are and if the suggestion is a proper match for the IC. Could the driver send additional data that causes a "pop" or "crackle"?
Interestingly, speaker-test never appears to produce the initial noise on playback
$ speaker-test -c2 --test=wav -w /usr/share/sounds/alsa/Front_Center.wav
, while mpg123 does (with a 16kHz mono MP3), also between tracks:
High Performance MPEG 1.0/2.0/2.5 Audio Player for Layers 1, 2 and 3
version 1.23.8; written and copyright by Michael Hipp and others
free software (LGPL) without any warranty but with best wishes
Decoder: generic
Trying output module: alsa, device: <nil>
Using default module dir: /usr/lib/arm-linux-gnueabihf/mpg123
Module dir: /usr/lib/arm-linux-gnueabihf/mpg123
Module path: ./output_alsa.so
Chosen output module: alsa
...
Audio driver: alsa
Audio device: (null)
Audio capabilities:
(matrix of [S]tereo or [M]ono support for sample format and rate in Hz)
| s16 | u16 | s32 | u32 | s24 | u24 | f32 | s8 | u8 | ulaw | alaw |
------|-------|-------|-------|-------|-------|-------|-------|-------|-------|-------|-------|
8000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
11025 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
12000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
16000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
22050 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
24000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
32000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
44100 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
48000 | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S | M/S |
(specifying alsa works, specifying device index fails)
It's not in the file, I checked. And also, mplayer starts playing the identical file OK, but has "pops" between tracks, though specifiying mplayers audio output seems to almost eliminate the popping when changing tracks.
mplayer -msglevel all=6 -ao alsa file.mp3
MPlayer 1.3.0 (Debian), built with gcc-6.2.1 (C) 2000-2016 MPlayer Team
CPU: ARM
AUDIO: 16000 Hz, 2 ch, s16le, 24.0 kbit/4.69% (ratio: 3000->64000)
Selected audio codec: [mpg123] afm: mpg123 (MPEG 1.0/2.0/2.5 layers I, II, III)
==========================================================================
Building audio filter chain for 16000Hz/2ch/s16le -> 0Hz/0ch/??...
[libaf] Adding filter dummy
[dummy] Was reinitialized: 16000Hz/2ch/s16le
[dummy] Was reinitialized: 16000Hz/2ch/s16le
Trying preferred audio driver 'alsa', options '[none]'
alsa-init: requested format: 16000 Hz, 2 channels, 9
alsa-init: using ALSA 1.1.3
alsa-init: setup for 1/2 channel(s)
alsa-init: using device default
alsa-init: opening device in blocking mode
alsa-init: device reopened in blocking mode
alsa-init: got buffersize=32768
alsa-init: got period size 1024
alsa: 44100 Hz/2 channels/4 bpf/32768 bytes buffer/Signed 16 bit Little Endian
AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample)
AO: Description: ALSA-0.9.x-1.x audio output
AO: Author: Alex Beregszaszi, Zsolt Barat <joy@***.de>
AO: Comment: under development
Building audio filter chain for 16000Hz/2ch/s16le -> 44100Hz/2ch/s16le...
[dummy] Was reinitialized: 16000Hz/2ch/s16le
[libaf] Adding filter lavcresample
[SWR @ 0xb6841020]Using s16p internally between filters
[dummy] Was reinitialized: 44100Hz/2ch/s16le
[dummy] Was reinitialized: 44100Hz/2ch/s16le
Video: no video
Freeing 0 unused video chunks.
Starting playback...
alsa buffersize does not match the configuration's.
MPD (controlled by mpc) clicks/pops once when starting to play, but then apparently "streams" continuously so changing tracks does not cause any noise.
So, whatever causes the pops in the first place (hardware? driver?), some players seem to be better at avoiding that situation (opening/reconfiguring the device).
Any input on how to get to the root cause and fix it much appreciated!
**Further digging**
Configuring the ALSA plugins in the order plug -> dmix -> softvol -> pcm, results in mplayer giving an error:
[AO_ALSA] alsa-lib: pcm_dmix.c:1057:(snd_pcm_dmix_open) dmix plugin can be only connected to hw plugin
So, back to: plug -> softvol -> dmix -> I2S DAC (kernel PCM).
The configuration file can be written hierarchically as follows:
pcm.!default
{
type plug
slave
{
pcm
{
type softvol
slave
{
pcm
{
type dmix
ipc_key 1024
ipc_perm 0666
slave
{
pcm
{
type hw
card 0
}
#format "S16"
rate 32000
channels 2
period_size 2048 # bytes
buffer_size 32768 # usec
}
bindings
{
0 0
1 1
}
}
}
control
{
name "PCM"
card 0
}
}
}
}
Softvol's control is what shows up as mixer device in e.g. alsamixer. I'm still unclear on what ctl's do.
Alsa usually stores it's configuration/settings persistantly. This can cause stale mixer devices to appear.
This worked to remove them (use sudo):
rm /var/lib/alsa/asound.state # remove the state file
chmod -x /usr/sbin/alsactl # make alsactl non-executable to prevent settings being written on shutdown
<REBOOT>
chmod +x /usr/sbin/alsactl
With mplayer and 32kHz audio only occasional pops when changing tracks. Increasing the buffer size seems to have solved occasional "stuttering / echo" playback.
dmix is the plugin removing most of the pops on play/stop. It [occasional pops changing tracks with mplayer] does not make a noticable difference whether the sources or the default rate is set in dmix slave's rate.
Device tree overlays (link to documentation below):
$ ls /boot/overlays
adau1977-adc.dtbo fe-pi-audio.dtbo iqaudio-dacplus.dtbo pitft28-capacitive.dtbo sdtweak.dtbo
adau7002-simple.dtbo goodix.dtbo iqaudio-digi-wm8804-audio.dtbo pitft28-resistive.dtbo smi-dev.dtbo
ads1015.dtbo googlevoicehat-soundcard.dtbo justboom-dac.dtbo pitft35-resistive.dtbo smi.dtbo
ads1115.dtbo gpio-ir.dtbo justboom-digi.dtbo pps-gpio.dtbo smi-nand.dtbo
ads7846.dtbo gpio-poweroff.dtbo lirc-rpi.dtbo pwm-2chan.dtbo spi0-cs.dtbo
akkordion-iqdacplus.dtbo gpio-shutdown.dtbo mcp23017.dtbo pwm.dtbo spi0-hw-cs.dtbo
allo-boss-dac-pcm512x-audio.dtbo hifiberry-amp.dtbo mcp23s17.dtbo qca7000.dtbo spi1-1cs.dtbo
allo-digione.dtbo hifiberry-dac.dtbo mcp2515-can0.dtbo raspidac3.dtbo spi1-2cs.dtbo
allo-piano-dac-pcm512x-audio.dtbo hifiberry-dacplus.dtbo mcp2515-can1.dtbo README spi1-3cs.dtbo
allo-piano-dac-plus-pcm512x-audio.dtbo hifiberry-digi.dtbo mcp3008.dtbo rotary-encoder.dtbo spi2-1cs.dtbo
at86rf233.dtbo hifiberry-digi-pro.dtbo midi-uart0.dtbo rpi-backlight.dtbo spi2-2cs.dtbo
audioinjector-addons.dtbo hy28a.dtbo midi-uart1.dtbo rpi-cirrus-wm5102.dtbo spi2-3cs.dtbo
audioinjector-wm8731-audio.dtbo hy28b.dtbo mmc.dtbo rpi-dac.dtbo spi-gpio35-39.dtbo
audremap.dtbo i2c0-bcm2708.dtbo mpu6050.dtbo rpi-display.dtbo spi-rtc.dtbo
bmp085_i2c-sensor.dtbo i2c1-bcm2708.dtbo mz61581.dtbo rpi-ft5406.dtbo tinylcd35.dtbo
dht11.dtbo i2c-bcm2708.dtbo papirus.dtbo rpi-proto.dtbo uart1.dtbo
dionaudio-loco.dtbo i2c-gpio.dtbo pi3-act-led.dtbo rpi-sense.dtbo vc4-fkms-v3d.dtbo
dionaudio-loco-v2.dtbo i2c-mux.dtbo pi3-disable-bt.dtbo rpi-tv.dtbo vc4-kms-v3d.dtbo
dpi18.dtbo i2c-pwm-pca9685a.dtbo pi3-disable-wifi.dtbo rra-digidac1-wm8741-audio.dtbo vga666.dtbo
dpi24.dtbo i2c-rtc.dtbo pi3-miniuart-bt.dtbo sc16is750-i2c.dtbo w1-gpio.dtbo
dwc2.dtbo i2c-rtc-gpio.dtbo piscreen2r.dtbo sc16is752-spi1.dtbo w1-gpio-pullup.dtbo
dwc-otg.dtbo i2c-sensor.dtbo piscreen.dtbo sdhost.dtbo wittypi.dtbo
enc28j60.dtbo i2s-gpio28-31.dtbo pisound.dtbo sdio-1bit.dtbo
enc28j60-spi2.dtbo iqaudio-dac.dtbo pitft22.dtbo sdio.dtbo
The overlay files are binary, but searching the sources at https://github.com/raspberrypi/linux/search?utf8=%E2%9C%93&q=hifiberry&type=
results in a few hits:
- https://github.com/raspberrypi/linux/tree/rpi-4.9.y/arch/arm/boot/dts/overlays
- https://github.com/raspberrypi/linux/blob/rpi-4.9.y/arch/arm/boot/dts/overlays/hifiberry-dac-overlay.dts
and further
- https://github.com/raspberrypi/linux/search?utf8=%E2%9C%93&q=pcm5102a&type=
- https://github.com/raspberrypi/linux/tree/rpi-4.9.y/Documentation/devicetree/bindings/sound
- https://github.com/raspberrypi/linux/search?utf8=%E2%9C%93&q=MAX98357A+&type=
- https://github.com/raspberrypi/linux/blob/rpi-4.9.y/sound/soc/codecs/max98357a.c
- https://github.com/raspberrypi/linux/blob/rpi-4.9.y/sound/soc/codecs/pcm5102a.c
So a specific driver exists. Is it available in Raspbian?
$ find /lib/modules/$(uname -r) -type f -name \*.ko | grep sound
/lib/modules/4.9.59+/kernel/sound/ac97_bus.ko
/lib/modules/4.9.59+/kernel/sound/drivers/mpu401/snd-mpu401.ko
/lib/modules/4.9.59+/kernel/sound/drivers/mpu401/snd-mpu401-uart.ko
/lib/modules/4.9.59+/kernel/sound/drivers/snd-virmidi.ko
/lib/modules/4.9.59+/kernel/sound/drivers/snd-dummy.ko
/lib/modules/4.9.59+/kernel/sound/drivers/snd-aloop.ko
/lib/modules/4.9.59+/kernel/sound/drivers/snd-mtpav.ko
/lib/modules/4.9.59+/kernel/sound/drivers/snd-serial-u16550.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm5102.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-pcm512x-i2c.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-adau7002.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-spdif-tx.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-sigmadsp-i2c.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-spdif-rx.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm8731.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-adau1701.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-cs42xx8-i2c.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-adau1977-i2c.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-ak4554.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm8804-i2c.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-pcm512x.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-sgtl5000.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm8741.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-pcm1794a.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm8804.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-arizona.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-tas5713.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-sigmadsp.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-adau1977.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-tpa6130a2.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-wm-adsp.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-cs42xx8.ko
/lib/modules/4.9.59+/kernel/sound/soc/codecs/snd-soc-pcm5102a.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-googlevoicehat-soundcard.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-rpi-cirrus.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-hifiberry-dacplus.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-hifiberry-amp.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-hifiberry-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-allo-piano-dac-plus.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-raspidac3.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-digidac1-soundcard.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-adau1977-adc.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-rpi-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-audioinjector-pi-soundcard.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-allo-piano-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-fe-pi-audio.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-allo-digione.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-dionaudio-loco.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-bcm2835-i2s.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-rpi-proto.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-allo-boss-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-hifiberry-digi.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-iqaudio-digi.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-pisound.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-iqaudio-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-justboom-digi.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-audioinjector-octo-soundcard.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-dionaudio-loco-v2.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-justboom-dac.ko
/lib/modules/4.9.59+/kernel/sound/soc/bcm/snd-soc-googlevoicehat-codec.ko
/lib/modules/4.9.59+/kernel/sound/soc/snd-soc-core.ko
/lib/modules/4.9.59+/kernel/sound/soc/generic/snd-soc-simple-card.ko
/lib/modules/4.9.59+/kernel/sound/soc/generic/snd-soc-simple-card-utils.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-hwdep.ko
/lib/modules/4.9.59+/kernel/sound/core/oss/snd-mixer-oss.ko
/lib/modules/4.9.59+/kernel/sound/core/oss/snd-pcm-oss.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-pcm.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-compress.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-timer.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-rawmidi.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-hrtimer.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq-virmidi.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/oss/snd-seq-oss.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq-midi-event.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq-device.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq-midi.ko
/lib/modules/4.9.59+/kernel/sound/core/seq/snd-seq-dummy.ko
/lib/modules/4.9.59+/kernel/sound/core/snd.ko
/lib/modules/4.9.59+/kernel/sound/core/snd-pcm-dmaengine.ko
/lib/modules/4.9.59+/kernel/sound/arm/snd-bcm2835.ko
/lib/modules/4.9.59+/kernel/sound/usb/snd-usb-audio.ko
/lib/modules/4.9.59+/kernel/sound/usb/caiaq/snd-usb-caiaq.ko
/lib/modules/4.9.59+/kernel/sound/usb/misc/snd-ua101.ko
/lib/modules/4.9.59+/kernel/sound/usb/6fire/snd-usb-6fire.ko
/lib/modules/4.9.59+/kernel/sound/usb/snd-usbmidi-lib.ko
/lib/modules/4.9.59+/kernel/sound/pci/ac97/snd-ac97-codec.ko
Nope.
Older effort to get driver going for different board: http://community.onion.io/topic/1761/resolved-attaching-pcm5102-to-omega2-i2s/13
This potentially shows how to make a matching device tree overlay and specify the driver (needs compiling?):
https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=8496&start=750#p1216305
**Update 2**
It must be caused by (re-)opening the device. With $ aplay -D default -c 2 -f S16 -r 48000 /dev/zero & the pops are gone with any player. But playing zeroes and software-mixing them seems a little CPU intensive:
$ w
18:21:38 up 1:17, 1 user, load average: 0.11, 0.15, 0.12
...
Kill it with
pi@raspberry:~ $ ps | grep aplay
16697 pts/0 00:00:28 aplay
pi@raspberry:~ $ ps aux | grep aplay
pi 16697 2.6 0.6 5828 2996 pts/0 SL 18:08 0:29 aplay -D default -c 2 -f S16 -r 48000 /dev/zero
pi 21159 0.0 0.3 4364 1764 pts/0 S+ 18:26 0:00 grep --color=auto aplay
pi@raspberry:~ $ kill 16697
pi@raspberry:~ $ Aborted by signal Terminated...
aplay: pcm_write:2011: write error: Interrupted system call
^C
[1]+ Exit 1 aplay -D default -c 2 -f S16 -r 48000 /dev/zero
pi@raspberry:~ $
(One could "autostart" this via an entry in /etc/rc.local.)
**Update 3**
MPD seems to have an option to "keep this audio output always open": https://www.musicpd.org/doc/user/config_audio_outputs.html But it seems to be for streaming only, since it does not affect pops on playback start:
sudo nano /etc/mpd.conf
audio_output {
type "alsa"
name "default"
# device "hw:0,0" # optional
# mixer_type "hardware" # optional
# mixer_device "default" # optional
mixer_control "PCM" # optional
# mixer_index "0" # optional
always_on "yes"
}
sudo service mpd restart
mpc play
mpc stop
Further measurements and comparison with audio recording show:
- IF the audible glitch/pop/crack occurs at the beginning of playback (I2S starting), it is visible on both speaker outputs as a positive spike
- I suspect it could by caused by the LRCLK starting approx. 500 us after BCLK
- datasheet shows different order in "TURN-ON RESPONSE (STANDBY MODE)"
So back to the I2S interface and driver
Building and running (warning: stopping the program even via desetup_io() does not stop the I2S) ...
~ $ git clone https://github.com/arisena-com/rpi_src
...
~/rpi_src/apps/i2s_test/src $ make
...
~/rpi_src/apps/i2s_test/src $ sudo ./i2s_test -t 2
starts the LRCLK on the third rising edge of BCLK and results in a nice ramp-up as shown in the datasheet, although BLCK starts first.
With i2s_test. Clock (yellow) starts two pulses before LRCLK (cyan). Audio out ramp-up visible on both channels (no pop or crackle):
Playing audio. Note glitch/ gap in clock (yellow, about 30 us clock followed by 150 us high). Output (pink/blue) seems undefined before pop occurs (at trigger) when LRCLK starts, about 30 ms before data starts (not shown):
Sometimes the pop isn't noticable, but the trace looks very similar.
So is it the BLCK glitch (what causes this, it's probably not intentional) or polarity (i2s_test starts from low-level) while regular operation has high-level?
So, let's try to use the appropriate driver as laid out in https://raspberrypi.stackexchange.com/a/74804/75483
[building the kernel takes probably a day or so, it's probably worth looking into cross-compiling..]
Although it seems to build OK (sound/soc/codecs/snd-soc-max98357a.ko), the pi0w does not appear to boot properly after, at least it does not connect to wifi. I'll have to hook it up to a display and HID.
I could not get a keyboard to work either, and it's not because I used a simple A-micro B adapter instead of a proper OTG adapter first.
Now I probably could attach to it via serial port...
The end of the working (Stretch lite default kernel) boot process output on serial looks like
[ 0.000000] Linux version 4.9.41+ (dc4@dc4-XPS13-9333) (gcc version 4.9.3 (crosstool-NG crosstool-ng-1.22.0-88-g8460611) ) #1023 Tue Aug 8 15:47:12 BST 2017
[ OK ] Started Configure Bluetooth Modems connected by UART.
[ OK ] Started Load/Save RF Kill Switch Status.
[ OK ] Started LSB: Resize the root filesystem to fill partition.
[ OK ] Started dhcpcd on all interfaces.
[ OK ] Reached target Network.
[ OK ] Reached target Network is Online.
[ OK ] Started Daily apt download activities.
[ OK ] Started Daily apt upgrade and clean activities.
[ OK ] Reached target Timers.
Starting OpenBSD Secure Shell server...
Starting Permit User Sessions...
Starting /etc/rc.local Compatibility...
My IP address is xxxx:xx:xxxx:xxxx:xxxx:xxxx:xxx:xxxx
[ OK ] Started OpenBSD Secure Shell server.
[ OK ] Started Permit User Sessions.
[ OK ] Started /etc/rc.local Compatibility.
Starting Daily apt download activities...
Starting Hold until boot process finishes up...
Starting Terminate Plymouth Boot Screen...
The image with custom kernel (no wifi, no keyboard) results in
[ 0.000000] Linux version 4.9.61+ (pi@raspberry) (gcc version 6.3.0 20170516 (Raspbian 6.3.0-18+rpi1) ) #1 Mon Nov 13 03:14:02 CET 2017
[FAILED] Failed to start Configure Bluetooth Modems connected by UART.
See 'systemctl status hciuart.service' for details.
[ OK ] Started dhcpcd on all interfaces.
[ OK ] Reached target Network.
Starting OpenBSD Secure Shell server...
[ OK ] Reached target Network is Online.
Starting LSB: Start NTP daemon...
[ OK ] Started Music Player Daemon.
Starting Permit User Sessions...
Starting /etc/rc.local Compatibility...
[ OK ] Started /etc/rc.local Compatibility.
[ OK ] Started Permit User Sessions.
Starting Terminate Plymouth Boot Screen...
Starting Hold until boot process finishes up...
[ OK ] Created slice User Slice of root.
[ OK ] Started Session c1 of user root.
Starting User Manager for UID 0...
Isn't WIFI and bluetooth on the same chip? No hardware info or actual schematics available from RPi Foundation.
pi@raspberry:~$ ifconfig wlan0
wlan0: error fetching interface information: Device not found
So I broke the Wifi. Any chance of reverting to the working kernel/configuration without losing my changes/files? Replace kernel files from working SD? No, replacing everything in /boot/ except for config.txt results in a hanging boot at
[ 2.930955] mmc1: new high speed SDIO card at address 0001
[ 22.411095] random: crng init done
So now I'll really have have to start fresh. I might be able to read my data from home dir by attaching the damaged system via USB OTG and card reader, something like
sudo mkdir /media/usb
sudo chown -R pi:pi /media/usb
sudo mount /dev/sda2 /media/usb
/media/usb/home/pi$ cp -r * ~
Maybe I should have updated first:
pi@raspberrypi:~ $ sudo rpi-update
*** Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS and Dom
...
*** Backing up modules 4.9.41+
...
*** depmod 4.9.62-v7+
*** depmod 4.9.62+
...
*** If no errors appeared, your firmware was successfully updated to 23b1614bb794dfce586f1300da75198befa4951d
*** A reboot is needed to activate the new firmware
pi@raspberrypi:~ $ sudo reboot
I might try again tomorrow (after making a backup).
No Wifi/IP after update (but wlan0 shown in
ifconfig)- set wifi-country with
sudp raspi-config(4 > I4)
- set wifi-country with
No need to enable
i2s-mmapnori2s, thehifiberry-dacoverlay does this automatically and mmap is available implicitly since 4.9 (April 2017).
**See https://github.com/raspberrypi/linux/issues/2212 about this exact issues and some I2S driver details**
Resources:
Raspberry Pi
Unofficial wiki: https://alsa.opensrc.org/
https://www.kernel.org/doc/html/v4.10/sound/soc/overview.html
