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Avery Fineman wrote:
You CAN realize a lowpass function in DSP but the TI chip inputs probably needs some sort of hardware lowpass filtering...? An anti-alias filter at the very least! The TI chip in question is actually a microcontroller rather than a DSP; I chose that based on desiring a low power design and only requiring one chip rather than two (although I'd grant you that there are some, e.g., SO-8 package serial interface ADCs out there that almost don't count as another chip...) and, uh, because I already have experience with it from other projects. It can sample up to ~200ksps, but I was shooting for a much lower rather (perhaps some 20-50 ksps) since there isn't much number crunching 'oomph' available. (I.e., no multipy-accumulate instruction. In fact, no hardware multiplier at all! :-) I'll build the mind-numbingly fast DSP monster receiver that can pull a signal 10dB beneath the noise floor and turn it into CD quality audio once I get the simple ones working.) Here's a good hint on melding hardware with software using DSP: "Scientist's and Engineer's Guide to Digital Signal Processing," by Stephen W. Smith, PhD, California Technical Publishing. How very interesting -- I actually have a copy of that with from Analog Devices (under a slightly different name); I always figured it was some third party and not the application engineers at Analog Devices that wrote it. Now I just have to crack the thing open... Good luck on that. It should be up and running within a month here. I've seen it claimed in text, but no details, that a quasi-lock could be obtained via voice, working on the harmonics of speech tones. I'm not going to buy that until I see a demo. I figured that's what they might have had in mind. Seems like a lot of effort to avoid sending a pilot tone (but then again, what else to use the aforementioned DSP for... oh, wait... fancy digital modulation schemes... ok...) ---Joel |
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