Dan Michaels email (remove spam text)
Josh Koffman wrote:
>I had an idea, and I wonder if it would work. Basically, I want to
>construct an 8 channel audio VU meter (level meter). This would be used
>on a mic/line level source rather than a speaker level source. I think
>there are dedicated chips for this, however I wondered if I could do it
>with a pic. If I used a 16f877, i'd have 8 analogue inputs, and I could
>use an 8 bit port for an 8 segment LED bar graph, and another 8 bit port
>to multiplex 8 of those bar graphs. I just am not sure that feeding the
>audio signal straight into the ADC would work. I know I would have to
>figure out the voltage range.
>Supposing this works, would it the be possible to make a small audio
>spectrum analyzer? Perhaps if I put a filter on each analogue input that
>only allowed one frequency, or a small frequency range through?
Writing this after reading some of the other responses:
- FFT on a PIC might be the worst way to go for this project.
Digital bandpass filters might be better - much less computation
intensive. Also, check a piclist thread a couple of months back
called "Don't use Microchip's FFT".
- many past audio systems have used h.w. bandpass filters, and this
would cetinaly work here too.
- if you really want VU meter functionality, you might need to consider
a logarithmic scale - and remember the PIC only has 8-bit A/D which
isn't gonna give you much dynamic range.
See also: www.piclist.com/techref/microchip/ios.htm?key=audio
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