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
- 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.