As you may recall, one of my current hobby projects is my Bodacious Acoustic Diagnostic Astoundingly Superior Spectromatic Display (a.k.a. BADASS Display). I will be the only one on my street to have one of these little beauties; how the neighbors will envy me (LOL).
The display itself is going to use about 10 meters of NeoPixels from Adafruit, all controlled by an Arduino Mega development kit, which is powered by a microcontroller from Atmel. Meanwhile, the audio stream from my iPad is going to be analyzed by a chipKIT MAX32, which is powered by a microcontroller from Microchip.
Now, one way to test this little beauty (when I finish building it, of course) will be to simply plug the audio output from iPad straight in and see what happens. Personally, however, I prefer to take things in stages. I've been thinking that it would be very handy to have an audio frequency generator that I could use to inject specific frequencies into the system to check its response.
This requirement was turned up a notch when my chum Steve Manley, who is currently blogging about one of his hobby projects, suggested I take a look at the MSGEQ7 Graphic Equalizer from SparkFun. (See: Hallway Lighting Project Using an Arduino & Adafruit NeoPixels.)
The MSGEQ7 chips are great. You feed an audio signal into one of your MSGEQ7s, which then filters out seven frequency bands centered around 63Hz, 160Hz, 400Hz, 1,000Hz, 2,500Hz, 6,250Hz, and 16,000Hz. I've decided to use these devices to test out the rest of the system before moving on to use digital signal processing (DSP).
I will be using two MSGEQ7 chips -- one for each audio channel -- but I actually purchased four of the little rascals, "just in case." Steve told me that he's bought a bunch of these, and that he really likes them, but that their sensitivity and response can be quite variable. Thus, he suggested using a frequency generator to feed the same frequency to all of the chips, to compare their, responses, and to pick the two with the closest match (I can also apply "fiddle factors" in software of necessary).
The end result is that I really need a frequency generator. Now, there are a variety of very tasty-looking frequency generator apps for the iPad, but I'm already using that over-worked little ragamuffin to generate the audio stream and as an oscilloscope using my Oscium iMSO-204.
My first port of call was to meander my way into the next bay and talk to my chum Ivan. Even though they don’t actually have a need for a frequency generator, Ivan rooted around under a bench and extracted a somewhat battered old case.
After blowing the dust off, he opened the case to reveal...
...something that scared the socks off me. I'm not quite sure what this is. I think it's a creation Ivan pulled together deep in the mists of time. He assured me that this would satisfy all my signal generating needs (once he'd worked out how to use it again), but I'm sad to say that I remained unconvinced.
Once more, Steve Manley came to the rescue. When I asked him what he used to test his sound-to-light creations, he pointed me at the FG085 MiniDDS Function Generator kit from those little scamps at SparkFun.
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