The USB Interface FAQ

This FAQ is written for people having problems with the BurrBrwon USB Audio Interfaces (PCM27.. and PCM29..)

1)    Nothing happens if connector is plugged in
        -    Measure Vbus (5V), have you not interchanged the connector cabels?
        -   Check cables and soldered device !
        -   Schort circuits are made very fast with this packages !
        -   Measure the resistance between the pins and the contact between device and signal trace an board !
        -   Check layout ! Wrong side? not mirrored?

2)    Unknown Device detected (found in Harware Manager), but nothing else.
        -    This will be displayed also if  the Vbus line must deliver power ( current is flowing)
        -    Check the SEL0,SEL1 Connections ! Are they connected to permanent 5V;3.3V via resistor?
              If not, connect them via 1.5k resistor directly to Vbus (5V)
        -    If the device runs hot (above 45 °C), check connections to USB Bus and to exeternal components.

3)   Device is detected, but no driver will be found

      -Solution: Edit ini File wdma_usb.inf

       Search the file wdma_usb.inf (normaly located in C:/Windows/System32) and open it with a text editor.
       Then search in the file  08bb . This is the vendor ID for BurrBrown.
       In the same line you would also find a string like "PID=". There you have to replace the number with 2902 (or whatever your Chip is)
       Save the file, unplug and replug your device and it will be recognized !

       An example .inf file can be emailed on request !

4)    No recording volume avalable

        This is correct beecause that BB has not implemented a Input Control in the Chipsets.
        Full input voltage is about 2Vpp, maximum (!) is 3.3Vpp

5)    The SPDIF Interface
       -    The Input is 3.3V and 5V compatible, don't worry about Level shifting!
       -    The Ouput is 3.3V Level only ! Don't connect directly to 5V CMOS Hardware, because maxim Hi Level is about 2.8 to 3 V !
             But a TOTX173 can be connected directly to this Output pin (minimum Hi Level=2V)
       -    SPDIF Output is always available (if you play music :-))
             The Output is the same Signal than the analog output.

      -     The SPDIF Input records, if signal is detected (and not copy protected)
             I've not tested the copy option !

6)    Nothing happens if plugged in. Even oscillator is not running.
         - Try to watch the oscillator directly after connecting power. Normally, oscillator only will oscillate some seconds and then STOPS,
            if no USB is connected
         - Try another XTAL. People told me, that some XTALs don't work (don't know why). After exchanging the XTAL, the board would work normally.
         - Try other XTAL capacitors (range up and down). Sometime this works. Also look after the parallel resitor (1 MOhm typical)
7)   Wondering why nothing at the digital input is recorded?
        - The PCM2902 is only capable of 16Bit. 24 Bit digital audio data wouldn't work !
          But the samplerate can be 32kHz, 44.1 kHz and 48 kHz
        - Is the digital audio source copy protected? If yes, the chipset will automaticly set the input to the analog one.
        - If you have a not copy protected source with the right data format, you can make a test (even if no audio data is transfered)
           If the chipset detects a clock at the digital input, it would automaticly switch to it. So, use a programm that can monitor the
           input level and if connecting the digital source, the input level would go dramaticly down (from about -50 dB to -80 dB and lower).

8)    Here is place for your questions.