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Old 5th February 2007, 02:37 PM   #1
Limhes is offline Limhes  Orkney Islands
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Default Can't get PCM2902 to work

I'm trying to make a PCM2902 USB sound card, using the (almost exact) schematic from the data sheet. Made a PCB, all connections are correct (as far as I can see) and there are no shorts. But, when I connect the device, Windows won't recognize it. I keep getting the message that there is a USB device connected, but it is not recognized.

You can find the schematic in the data sheet.

The PCB I made is attached, with and without silk screen. Does it matter that I used electrolytic capacitors instead of non-polars for the 1uFs? I replaced both ICs and it still doesn't work. There is a fine 5V USB voltage on the chip, but the !SSPND pin doesn't get high. I can't measure the crystal's signal, since I have no scope at hand. Is this very critical to layout?

Thanks in advance.

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Old 5th February 2007, 03:21 PM   #2
Limhes is offline Limhes  Orkney Islands
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Hmm, I can't edit the above post...

But, I just saw I didn't connect SEL1 and SEL0 to the positive supply voltage. But, even after doing that, it doesn't get recognized.
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Old 29th April 2008, 05:09 PM   #3
sexya is offline sexya  India
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i feel you need to swap the data pins probably you have mixed those up.. that why its not getting reconz.. i had some thing like lthis when i was fixing my mp3 player data cable and i had mixed up piins.. i am talking of the data + and data - pins not + vcc and ground... mind it.
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Old 30th April 2008, 08:21 AM   #4
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Hello Limhes,

check if your oscillator is working.

If not, try different values for the capacitors near the crystal.

You need a scope to see if the oscillator is working properly!

Andreas
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Old 30th April 2008, 02:22 PM   #5
gmarsh is offline gmarsh  Canada
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The 1Mohm resistor in parallel with the crystal has to be there.

I left this out on a PCM2906 design, it would detect as a USB device in this case but wouldn't go any farther, same as what you're seeing.
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Old 3rd May 2008, 02:26 AM   #6
Archwn is offline Archwn  United Kingdom
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For the record. Electrolytic caps can be used with no problem. Even the modest Nichicon Muse FW. I suggest 10uF would do the job. I didn't say it is the best to use electrolytic though.

Some reports that after pull in/out for a while, this guy might just wake up and work at anytime.

As I can't see the posted pictures, I can't comment.
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