EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: billfernandez on June 22, 2016, 04:08:19 am
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I'm working on an audio project that I hope to be able to turn in to a product for sale. As part of it I want to create some LED bargraph level meters with features that can't be implemented with a simple resistance ladder and stack of comparators (e.g. with LM3915 chips).
I have been looking (so far unsuccessfully) for a chip that has a 12-bit ADC that can run at at least 40K samples/second, a microprocessor that can compute which LEDs I want turned on under various conditions (to show "average", "peak", etc.), can control 16 LEDs (the bargraph), and is dirt cheap. ADC performance (noise, ENOB, etc.) doesn't have to be particularly good. I'll need four meters per device, so instead of one chip per meter I could use a multi-input ADC, and control four LED-driver chips over a serial bus.
Can anyone point me to a chip or chip family that might suit my needs? Thank you.
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I know it's not quite the same specs that you're after, but Silicon Chip magazine here in Australia has a micro-controller based VU meter on their latest issue. Could be handy for some ideas:
http://www.siliconchip.com.au/Issue/2016/June/Stereo+Audio+Level-VU+Meter%3A+Add+Bling+To+HiFi+System (http://www.siliconchip.com.au/Issue/2016/June/Stereo+Audio+Level-VU+Meter%3A+Add+Bling+To+HiFi+System)
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ANY dsPIC33e/f
ANY cortex m3/m4
one MCU i've been using lately:
dspic33ep64gs504 -> http://ww1.microchip.com/downloads/en/DeviceDoc/70005127c.pdf (http://ww1.microchip.com/downloads/en/DeviceDoc/70005127c.pdf)
-140 MHz/ 70 MIPS
-the family has up to 4 + 1 ADCs on board that can go up to 3.25 MS/s each, around 11 ENOB
-up to 2 12 bit dacs
-lots of the other stuff (timers, pwm, communication interfaces, ...)
-dsp can handle fixed point math
a bit pricey though, around a stm32f427.
anyway, this has 5 independent ADCs, but most of the other dspic33 have the single adc that can work in "mode 2" which means higher throughput one channel or four channel truly-10 bit acquisitions so if 10bit is ok you can use a much cheaper part (in the order of 1~2€)
there are a lot of arm mcus as well with simillar characteristics so whatever you choose if you can handle efficiently the conversion sequence you don't even need to use an external adc that will cost at least as much as the mcu with no true benefits
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Cortex Mx come with CMSIS-DSP library with FFT functions.
http://stm32f4-discovery.net/2014/10/stm32f4-fft-example/ (http://stm32f4-discovery.net/2014/10/stm32f4-fft-example/)
http://www.keil.com/pack/doc/CMSIS/DSP/html/index.html (http://www.keil.com/pack/doc/CMSIS/DSP/html/index.html)
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I know it's not quite the same specs that you're after, but Silicon Chip magazine here in Australia has a micro-controller based VU meter on their latest issue. Could be handy for some ideas:
http://www.siliconchip.com.au/Issue/2016/June/Stereo+Audio+Level-VU+Meter%3A+Add+Bling+To+HiFi+System (http://www.siliconchip.com.au/Issue/2016/June/Stereo+Audio+Level-VU+Meter%3A+Add+Bling+To+HiFi+System)
Thank you! This is highly relevant, very useful and amazingly timely.
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Check this
http://www.ebay.com/itm/LED-Music-Spectrum-Display-Analyzer-MP3-PC-Amplifier-Audio-Level-Indicator-kits-/331734664602?var=&hash=item4d3ced459a:m:mFAX1kyBnHbrqhWlMoYY3fQ (http://www.ebay.com/itm/LED-Music-Spectrum-Display-Analyzer-MP3-PC-Amplifier-Audio-Level-Indicator-kits-/331734664602?var=&hash=item4d3ced459a:m:mFAX1kyBnHbrqhWlMoYY3fQ)
You can make your specif firmware
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JPortici & Jeroen3: Thank you for your uP recommendations. It will take me awhile to look into them.
ebclr: I searched and found a video of this in action. It looks like it's just making up random stuff. But I ordered one anyway to see what's driving all those LEDs.
Thanks everyone.
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Also lock at this site
http://www.barmeter.com/cn/index.asp (http://www.barmeter.com/cn/index.asp)
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"has a 12-bit ADC"
It must be designed for golden ear types, :)
After having finished your project, you can try to experiment lower adc resokution. I think you will be disappointed in how insensitive your eyes are: most likely, as I cannot rule out the remote possibility that you have Superman eyes and brain, that your eyes couldn't tell a meter based on a 12bit adc or a 8bit adc.
From my personal experience.
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"has a 12-bit ADC"
It must be designed for golden ear types, :)
After having finished your project, you can try to experiment lower adc resokution. I think you will be disappointed in how insensitive your eyes are: most likely, as I cannot rule out the remote possibility that you have Superman eyes and brain, that your eyes couldn't tell a meter based on a 12bit adc or a 8bit adc.
From my personal experience.
I agree. My bargraph will only have 16 LEDs, not 4096. I've chosen 16 levels to display across an 80dB amplitude range -- not evenly distributed across that range. My calculation is that to be able to detect the sixteen levels I want I'll need the resolution of a 12-bit ADC. So I thought I'd start by seeing if there are cheap chips available for this. If not, then I'll have to devise another approach to getting the results I want.
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"My bargraph will only have 16 LEDs, not 4096."
A bargraph is naturally ligrithmic. And depending on the base, a 12led bar for example can display 12adc on a baase of 2, or 19 bit adc on a base of 3, ......