dickelec
Posts: 2
Joined: Thu Feb 07, 2013 2:57 pm

USB sound card not detected on power up

Thu Feb 07, 2013 3:13 pm

I have a PCM2704 sound card connected to my Raspberry PI. It works well, without audio glitches and the sound quality is good but there is one problem. It is not detected on power up. removing and replacing the USB connector causes it to be detected and operate normally. the command 'lsusb' shows the device absent until disconnected and reconnected. After a 'shutdown -r now' the USB sound card comes up working. Does anyone have an idea how I might fix this?

Thank you

ski522
Posts: 394
Joined: Sun Sep 30, 2012 2:22 pm

Re: USB sound card not detected on power up

Thu Feb 07, 2013 4:32 pm

That's odd, it should detect upon power up. Sounds like hardware problem with either the Pi or the sound card. When you power up (without the card being detected) what does the contents of dmesg show? Open a shell and type dmesg <enter>.

Also, what are the specs of your power supply?

dickelec
Posts: 2
Joined: Thu Feb 07, 2013 2:57 pm

Re: USB sound card not detected on power up

Thu Feb 14, 2013 3:55 pm

I have solved this problem. It was hardware. The USB card with a PCM2704 chip was purchased as a kit from Ebay, (I could not find a ready made converter from the 'verified peripherals' list). When it failed to connect, a log entry indicated that a USB device was taking too much current. The PCM2704 should not have taken more than 100 milliamps so I investigated the circuit. I found the power supply smoothing capacitors to be 100 microfarads where the chip datasheet showed 1 microfarad capacitors. I changed them (to 10 miccrofarads) and it now works. The USB card is detected on power-up.

As part of my investigation, I connected a UBS hub, a NLUSB2-224P. It did not work until I set the Raspberry PI USB speed to USB 1 by adding the command dwc_otg.speed=1 to the end of the /boot/cmdline.txt file.

Thank you

audioplastic
Posts: 12
Joined: Tue Jan 15, 2013 12:51 am
Location: Cambridge

Re: USB sound card not detected on power up

Fri Feb 22, 2013 3:23 am

Thanks for a solution. I was having the same problem with a kit board based on the 2704. I find that you don't get the inrush current problem if no load is connected to the line out, but this sucks a bit as you have to remember to disconnect the load, power the RPi, then reconnect the load. It is not just the RPi that complains - I get overload warnings on both a Mac and PC also.

Was the PCB that you got in the kit white with a JSDZ logo by any chance?

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