@David: "However that leads me to my question...with only 7 frequency bands and 2 channels will your BADASS display now only have 14 channels instead of the 16 in the diagram?"
I notice that you can set the oscillator frequency of the chip externally. I wonder if you could intentionally skew the oscillator frequency of a second chip being fed the same audio input to get some extra bands in between the intended ones?
@Rcurl....nice idea. I saw a similar thing done recently with the good old LM3915 LED level meter chips to give 1dB increments instead of the usual 3dB. And I got some chips that generate and provide a notch filter for 2600Hz tones used in Radio keying systems, I was going to underclock them to get the notch down to 1000Hz. However in this case, according to Max's diagrams, the bands are fairly wide anyway, so I don't know if you'd really gain much here?
@Rcurl: I notice that you can set the oscillator frequency of the chip externally. I wonder if you could intentionally skew the oscillator frequency of a second chip being fed the same audio input to get some extra bands in between the intended ones?
Yes, you can adjust the 33 pF and 200 kohm RC values to achieve different clock frequencies. However the filters are quite wide, so the effect would be minimal. Others have found the interpolation technique in firmware gives better results.
I read the headline and thought that must be another one of Max's ideas :-) neat chip, but I reckon a, ARM M4 could probably do the lot with some tight coding. Of course if you want a low power version difinitely the way to go.
It was the name of course that I'm talking about :-) reminds me of an April 1st edition of Electronics Australia back in the 70's where a bunch of much more believable acronyms were similarly well chosen.
@David: However that leads me to my question...with only 7 frequency bands and 2 channels will your BADASS display now only have 14 channels instead of the 16 in the diagram?
Thsi is something I've been pondering -- I think interpolating between two channels to create an additional channel would give me a quick fix. Of course, when I move onto doing all thus in software using an FFT (or similar algorithm), I'll be able to split things up into as many "buckets" as I wish.
Another approach - use the Teensy 3.1 and audio shield from pjrc.com. You only need one processor which is Arduino compatible so you can use the Neopixel libraries. They have a really nice audio DSP library including up to 1024 bin FFTs for the ARM M4 core. Teensy board about $20, audio sheild about $15. It will blow the doors off your solution:
I'm not associated with PJRC but I am very impressed with their products. I beleive they also have a high performance LED strip driver too.
@rheslip0: Another approach - use the Teensy 3.1 and audio shield from pjrc.com. You only need one processor which is Arduino compatible so you can use the Neopixel libraries.
Actually, you can't use any-old-NeoPixel library -- the ones from AdaFruit, for example, use low-level assembly code to get the timing right. However PRJC also does a NeoPixel library that drives 8 strips using the DMA Engine.
When I last talked to Paul at PRJC, they were still working on the audio library. I'm delighted to hear that it's finished -- I'm designing my BADASS display in such a way that I'll be able to swap out my first-pass solution (chipKIT + Arduino) for a Teensy 3.1-based solution -- it will be fun to play with that -- but one step at a time LOL
Max, It was in 1983 that Elektor published the first hardwired modular(op amp and CMOS logic IC based) real time spectrum analyser display article using a Futaba VF Display (14X10 dot matrix display used for lift panel display). At about the same time, Itron, NEC and futaba also developed multicolor VFD spectrum analyser displays which were much more attractive than the colour LCDs used thesedays. May be future OLED displays may match their beauty.The dots were actually small(1mmx5mm) coloured rectangular tidbits and glew in bright green, lemon and red colours. Blue and orange were added later. The tidbits were so cute that one felt like picking them off the display and eating them.A little later, SCF (switched capacitor filter) technology has become popular and digital clock based filters were cried to be used in HAM radio, and audio spectrum analyser filter applications.Exar has pioneered these ICs (along with EG and G Reticon R6520) in the form of XR1092 and other ICs.Sanyo has then designed several Integrated spectrum analyser with display driver ICs with I2C interface. EXAR's SCF line got affected as there was some problem with ROHM, which was their foundry then.ROHM also made BA series of SCF filter ICs.National and Max made a number of SCF ICs. NJRC (New japan Radio corp) has then developed a serial audio DSP which was dedicated for digital audio spectrum analyser application and was obsoleted about a decade ago.Yamaha also had a similar series of serial DSP ICs.Fortunately, Mixed signal integration continues making these wonderful SCF ICs available. Even now a number of branded graphic equalisers with VFD spectrum analyser are traded on ebay.
Thanks for your nice blogs.It is heartening to note a number DIYs keeping this alive and kicking.
@Rama: Thanks for your nice blogs.It is heartening to note a number DIYs keeping this alive and kicking.
Thank you for your kind words -- I must admit that by aroudn 2000 i was starting to get worried that hobby electronics was on the way out -- but then the Maker Movement suddenly went mainstream and now building things is cool again (Happy Dance)
@JAmbrose...Good to see you pushing these very natty chips you make. but it strikes me you have been hiding your light under a bushel - I had never heard of you before now, but will certainly have a look at what you offer.
(I think you need to pay Max a commission if he hasn't already asked :-)
(PS @Max - if this causes you to get commission, I want a cut :-))