Digital Preamplifier and TI

[kami10001]

hello all,

I m v.new here. I m currently working on TMS320C6711 DSP Starter Kit (DSK Board). I have to transfer digital data from Music CD (44.1 kHz+16 or 24 bit) on to the DSK board and then perform 4 steps.
1-Interpolation: 44.1->88.2
2-Decimation: 88.2->44.1
3-SRC for Rational Factor: 44.1->48
4-Multistage SRC: 44.1->192

I have to program this DSK to function as a preamplifier and listen to the audio after all the above operations r performed on the digital audio input. TI's Code Composer Studio (C & Assembly) is to b used.

ANY one out there, who is familiar with these things in any respect must (plz) reply to this post as i m in a big trouble.

regards.

[kami10001]

plz help if any body knows how to cop up with this problem.

[MWP]

Sounds like a school/uni task... sure your not trying to cheat on your homework?

[roibm]

Originally posted by MWP
Sounds like a school/uni task... sure your not trying to cheat on your homework?

got him, ha?

[kami10001]

ya this is, can't anyone help in this regard

[gmarsh]

Doing this sort of work is half of my day job

You just described 4 polyphase filters. There's probably lots of examples and functions in the TI software which can do a lot of this for you, most of your work will involve calculating filter taps.

[kami10001]

ok gmarsh

can u guide me throught the process

i mean where to start, just guide me then once i got the right track, i will follow it on my own & what type of things do TI offer? can u plz spend some time to write this all stuff just once??

[gmarsh]

Originally posted by kami10001
ok gmarsh

can u guide me throught the process

i mean where to start, just guide me then once i got the right track, i will follow it on my own & what type of things do TI offer? can u plz spend some time to write this all stuff just once??

ok, first things first - i'm not doing your work for you.

I haven't programmed on TI DSPs in years and I've never used a C67x DSP, so I don't recall what examples they have. If you're using one of their evaluation boards with onboard sound or onboard digital audio I/O hardware, then without a doubt the board comes with some software examples - eg, a talkthrough example.

Tackle the first thing (44.1->88.2) first... here's what you need

- two audio interfaces on the board, one at 44.1 and one at 88.2, which are synced together.
- the DSP's McBSPs (or whatever they call them now) properly configured.
- your audio processing code, which reads one sample from the 'incoming' McBSP port and writes two samples to the 'outgoing' port.

And in order to write the audio processing code, you'll need:

- to decide what the frequency characteristics of your 44.1->88.2 conversion need to be (passband ripple, transition band, stopband ripple) - eg. 0.005dB passband to 20KHz, 100dB attenuation at 22.05KHz.
- Feed this into a filter design program. Design a filter with an even number of taps, with the aforementioned characteristics and a sampling rate of 88.2KHz. Personally I use MATLAB's "fdatool" for this.
- Divide the filter into two polyphase banks. You'll need to multiply the tap values by 2.
- Either write the code for a 2X polyphase FIR filter, or see if you can find a library function which does it for you.

Once you get this done, you can move onward to the more difficult 44.1->48 kind of stuff.

If you don't know what I'm talking about here, pick up a filter design book and start reading TI appnotes.

[kami10001]

thank u v.much gmarsh, i will try these things out.

I have started reading all the documents that TI provide with the card, hope i will find one that can solve a part of my problem

[kami10001]

[QUOTE]Originally posted by gmarsh


Tackle the first thing (44.1->88.2) first... here's what you need

- two audio interfaces on the board, one at 44.1 and one at 88.2, which are synced together.


1-How to define 2 audio interfaces on the board? u mean just to configure 2 McBSP(Incoming McBSP0 & Outgoing McBSP1) for recieving data from CD-drive or PC & sending back data on the board, one (McBSP0) @ 44.1 for recieving data & other (McBSP1) @ 88.2 for sending data back to PC

- your audio processing code, which reads one sample from the 'incoming' McBSP port and writes two samples to the 'outgoing' port.

2-U mean one sample should b read from the audio interface McBSP0 & two samples should b write on McSBP1

OR

the 2 audio interfaces r different from the incoming/Outgoing McBSP.then y they r defined?

Need a quick reply....