From: "Frank Bemelman"
Subject: Re: Questions regarding the PIC16C77X and its built in ADC
Date: Mon, 23 Sep 2002 21:31:57 +0200
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> > What are you going to do with all those samples? The PIC does not have
> > ram to store them. The only thing you can do (IMO) is measuring the time
> > each period of the input signal.
> I should have explained what I am going to do with the signal in the
> original post, as it will (I think) justify using 12 bits. Basically, I am
> wanting to sample input from a telephone, encode that input into mu-law
> audio format, and then send that data over a LAN to another machine. I
> a company that sells boards that use the CS8900 ethernet chips
> and kits), as well as a tutorial on how to send UDP packets over an
> link using it. Right now however, I am more concerned with sampling the
> signal from the telephone, to make sure my basic design (on that end of
> things) is correct, as well as if there are things I am forgetting. So,
> the basic design sound ok in my original post? (i.e. what pins should be
> connected to RING and TIP, where the battery should be connected, and
> the resistor should be?)
I have no idea.
> > The sampling rate of 8KHz looks allright. You don't need 12 bit
> > 8 bits is more than enough. Use the 8 MSB of the ADC.
> Since I need to reproduce an accurate digital representation of the input
> signal from the telephone, and the bandwidth that the original data takes
> approximately 4000 hertz, I would think I would need a 12 bit resolution
> higher), otherwise I will get a rather high quantization error rate. Since
> am wanting to accurately reproduce the voice on the machine that the
> are being sent to over the ethernet link, I would think I would need at
> least a 12 bit resolution. Is this not correct?
I don't know, you could try recording it with a simple windows program,
testing various samplerates at 8 bit. See how that goes. OTH, it doesn't
hurt either, so, indeed, why not use all the available bits.
I'm not very helpful eh?
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