[PROBLEM] MPD error "Failed to open ALSA" only occurs after coldstart

[gforster]

Hello world,

I am new to this forum and have read through the forum rules. I also saw that there are several entries related to "MPD error" and "Failed to open ALSA".
First, I wanted to thank Tim for this great audio player. A friend of mine and I first wanted to build our audio players based on Volumio, but then we found moode audio player which offers much more options.

We did build two versions of audio players. Both are based on a Raspberry Pi 3B+ and are running the latest moodeaudio 6.4.x version, but are using two different I2S audio HAT cards:
(1) Suptronics X400 V3.0
(2) IQaudIO Pi DigiAmp+

The problem I am describing is valid for both types of audio cards (1) and (2) above. It does, however,  ONLY occur during a  coldstart.
When I say coldstart, I mean switching-on the external AC/DC power supply (230VAC 50Hz, 12VDC@3A) and powering-up the hardware.
The problem is reproduceable and occurs every time I perform a coldstart.

The problem does not occur when performing a warmstart, ie moode audio player restart/reboot or when executing an SSH "sudo reboot" command.


Here are the "moodeutl -l" logs:

---

Coldstart (bad case):
20200419 193009 worker: -- Start
20200419 193009 worker: Successfully daemonized
20200419 193010 worker: Integrity check (passed)
20200419 193010 worker: Session loaded
20200419 193010 worker: Debug logging (off)
20200419 193010 worker: Device raw: (0:|1:empty|i2s:IQaudIO Pi-DigiAMP+)
20200419 193010 worker: Device cfg: (IQaudIO Pi-DigiAMP+|0|0|Digital|0)
20200419 193010 worker: ALSA volume set to (Invalid card number.)
20200419 193010 worker: -- System
20200419 193012 worker: Host name     (moode)
20200419 193012 worker: moOde release (6.4.2 2020-02-12)
20200419 193012 worker: Raspbian OS   (10.2)
20200419 193012 worker: Linux kernel  (4.19.97-v7+ #1293)
20200419 193012 worker: Platform      (Pi-3B+ 1GB v1.3)
20200419 193012 worker: Architecture  (armv7l)
20200419 193012 worker: MPD version   (0.21.16)
20200419 193012 worker: CPU governor  (ondemand)
20200419 193012 worker: USB boot enabled
20200419 193012 worker: File system expanded

---

Warmstart (good case):
20200420 140848 worker: -- Start
20200420 140848 worker: Successfully daemonized
20200420 140848 worker: Integrity check (passed)
20200420 140848 worker: Session loaded
20200420 140848 worker: Debug logging (off)
20200420 140848 worker: Device raw: (0:IQaudIODAC|1:empty|i2s:IQaudIO Pi-DigiAMP+)
20200420 140848 worker: Device cfg: (IQaudIO Pi-DigiAMP+|0|0|Digital|Invalid card $
20200420 140848 worker: ALSA volume set to (0%)
20200420 140849 worker: -- System
20200420 140850 worker: Host name     (moode)
20200420 140850 worker: moOde release (6.4.2 2020-02-12)
20200420 140850 worker: Raspbian OS   (10.2)
20200420 140850 worker: Linux kernel  (4.19.97-v7+ #1293)
20200420 140850 worker: Platform      (Pi-3B+ 1GB v1.3)
20200420 140850 worker: Architecture  (armv7l)
20200420 140850 worker: MPD version   (0.21.16)
20200420 140850 worker: CPU governor  (ondemand)
20200420 140850 worker: USB boot enabled
20200420 140851 worker: File system expanded


What I suspect is, that the audio card - independent whether it is the Suptronics or the IQaudIO - is not yet fully initialized when it is beeing accessed during the boot sequence. What makes me believe in my theorie is that the radio perfectly works after a warmstart. At a warmstart condition, the radio (Pi and the audio card) are continuously powered and the audio card is fully initialized.


So my question to the forum is the following: 
Is there a way to slow-down / pause the boot sequence for a second or so before moode / ALSA tries to access the audio card?
This would probably give the audio card sufficient time to complete it's init phase and respond correctly to any command.



thx & brgds,
Gerhard