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Audio questions : i2s, dac, oversampling, PIC, FPGA ...

Started by yannouch November 30, 2004
Hello,

I have a board with an embedded PowerPC (mpc8241), on which there is
no audio hardware. I want this board to have audio capabilities. I
have serial ports, usb ... but no i2s, which is, from what I've
understood from my previous readings, the bus needed  to control a
DAC.

I'd like the sound data to be oversampled to 192kHz. (let's say I have
a HDD connected to this board and it contains 44.1 kHz PCM data
files.)

Actually my idea is to do smthg like :

MAINBOARD == i2s ==>(OVERSAMPLING?)===> DAC ===> Analog output

with mainboard separated from the rest of the hardware, in order to be
able to plug to it High-Fidelity/High-Quality Audio-DAC

 
So my questions are :

1. Where the oversampling must be done ? in processor ? with a
dedicated hardware ? Before being sent to i2s bus ? after the firts
device (DAC?) on i2s bus ?

2. How can I get this mainboard to have i2s capabilities ? I've
searched a bit, and I think I've understood I should use a dedicated
microcontroller (PIC ? FPGA ?) attached to the main microprocessor.
True ? If I have an i2s bus, can I have the audio DAC separated from
main board, just linking them via the i2s wires ?

3. where can I find some good quality Audio DAC kit, taking data from
i2s bus, sending Analog audio to RCA plugs ?


Thanks

Yann
yann@yannouch.net (yannouch) wrote in message news:<84158b3a.0411300912.593bcba3@posting.google.com>...
> Hello, > > I have a board with an embedded PowerPC (mpc8241), on which there is > no audio hardware. I want this board to have audio capabilities. I > have serial ports, usb ... but no i2s, which is, from what I've > understood from my previous readings, the bus needed to control a > DAC. >
I2S is a protocol primarily designed for streaming sound between DAC and a host controller. Controlling of the DAC is usually done via another bus such as I2C, L3, microwire etc. So apart from making sure that you can do I2S for streaming, you should also consider an another bus to control the DAC. Search out the Philips Semiconductor site for info on the I2S. good luck.
yann@yannouch.net (yannouch) wrote in news:84158b3a.0411300912.593bcba3
@posting.google.com:

> Hello, > > I have a board with an embedded PowerPC (mpc8241), on which there is > no audio hardware. I want this board to have audio capabilities. I > have serial ports, usb ... but no i2s, which is, from what I've > understood from my previous readings, the bus needed to control a > DAC. > > I'd like the sound data to be oversampled to 192kHz. (let's say I have > a HDD connected to this board and it contains 44.1 kHz PCM data > files.) > > Actually my idea is to do smthg like : > > MAINBOARD == i2s ==>(OVERSAMPLING?)===> DAC ===> Analog output > > with mainboard separated from the rest of the hardware, in order to be > able to plug to it High-Fidelity/High-Quality Audio-DAC > > > So my questions are : > > 1. Where the oversampling must be done ? in processor ? with a > dedicated hardware ? Before being sent to i2s bus ? after the firts > device (DAC?) on i2s bus ? > > 2. How can I get this mainboard to have i2s capabilities ? I've > searched a bit, and I think I've understood I should use a dedicated > microcontroller (PIC ? FPGA ?) attached to the main microprocessor. > True ? If I have an i2s bus, can I have the audio DAC separated from > main board, just linking them via the i2s wires ? > > 3. where can I find some good quality Audio DAC kit, taking data from > i2s bus, sending Analog audio to RCA plugs ? > > > Thanks > > Yann >
Maybe I'm missing something... But why not just use a USB sound card?