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Old 19th August 2011, 04:38 PM   #1
srubin is offline srubin  United States
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Default TI USB DAC - PC side

Hi,

I'm pretty new ate this and my question might seem really basic, sorry...

If i build a device with the TI Audio USB DAC (like PCM2704), when I connect the circuit to teh PC, does teh PC immediatly recognize that this is an audio device and starts sending audio to it. or do I need to prepare some software for the PC side?

Please excuse my beginner level.

thanks

Sam
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Old 19th August 2011, 08:33 PM   #2
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All the details requiring the USB interface and how to configure the hardware.

This is the important part I believe though.

Quote:
D+ should be pulled up with a 1.5-k Ω ( 5%) resistor. To avoid back voltage in self-powered operation, the device must not provide power to the pullup resistor on D+ while V BUS of the USB port is inactive.
If the device is being powered by the USB cable then D+ is only pulled high when the USB cable is connected, so no special measures need to be taken.

However if you are going to power it from a dedicated separate supply then you will have to provide a logic gate that will only pull D+ high when the USB cable is plugged in. In my implementation I have it set so that when the standard 5volt line of the USB cable is plugged in D+ is pulled high via a logic gate.

Providing you've done what is necessary then yes, as soon as you plug the device into a USB port the computer will recognise it as a generic USB sound controller, it will install the required device driver and the chip will start functioning. In some situations you might have to tell windows that the USB sound card is to be used as the primary sound card for it to work with some applications.

One word of warning though, I have had a situation where the PCM270x wasnt recognised by a laptop and I could not figure out why. Same copy of windows, same service pack with the same drivers as another PC, except it would not work with it. On all other machines and laptops no problems and this was self powered rather then relying on the USB line.
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Old 22nd August 2011, 12:40 AM   #3
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Quote:
Originally Posted by 5th element View Post
All the details requiring the USB interface and how to configure the hardware.
That should have read -

All the details requiring the USB interface and how to configure the hardware are in the datasheet.
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Old 22nd August 2011, 01:16 AM   #4
srubin is offline srubin  United States
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Quote:
Originally Posted by 5th element View Post
That should have read -

All the details requiring the USB interface and how to configure the hardware are in the datasheet.

Thanks! very helpful
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