Spectrum analyzer users custom characters on an HD44780 display

[Camilo] built a spectrum analyzer to use with his audio system (translate). The hardware is quite simple, using an op-amp, microcontroller and LCD display. He chose an LMV324M low-voltage op-amp which connects to the incoming audio signal and feeds its output to the microcontroller’s ADC. In this case, he chose a Freescale microcontroller from the HCS08 family which is running at 20 MHz. This gives the project enough speed to properly analyze the incoming audio. He mentions that he’s following the guidelines set forth in the Nyquist-Shannon sampling theorem and using the Fast Fourier Transform when processing the samples.

This isn’t the first time we’ve seen a character LCD used as a display for a frequency analyzer. This other ATmega8-based rendition supported several different screen layouts. These displays have enough RAM to store eight custom characters. Each character is 5×8 pixels, lending eight levels to each character for a total of 16 for each column seen above. We love the simplicity of the hardware in the project but we wouldn’t mind seeing an additional potentiometer to fine-tune how the data is displayed on the screen to take advantage of its full range. See the project in action in the clip after the break.


  1. kj says:

    i’d like to see it responding to a sweep signal or something similar.

    from the current song selection is difficult to see if it is responding correctly and whether it’s experiencing any noticeable latency.

    • Jac Goudsmit says:

      I agree. Particularly, it looks like the leftmost bar is showing the full spectrum…

      Still: Nice project!

      • jjr says:

        Agreed. Regardless, great eye-candy.

      • MysticPixel says:

        re: left most bar: may be, or it may just be showing extremely low frequencies, which often show up essentially as artifacts in some tracks. Use a good software spectrum analyzer (there’s one really good Winamp plugin called “DSP Spectrum Analyzer” that actually does it accurately with a high degree of detail) and you’ll see what I mean…

        Very cool, I’ve been wanting to do something like this with a LED marquee for a while but it’s gonna need some CPU horsepower, don’t think a Cortex-M3 will cut it so I’ll have to take a closer look at this one.

  2. xorpunk says:

    I’m actually looking to use one with a MICF007 for 300Mhz-450Mhz detection and logging soon, it’ll be a handheld unit.

  3. Hatstand_UK says:

    Shouldn’t the title read “Spectrum analyzer uses custom characters on an HD44780 display”

    Nice project btw!

  4. vinod says:

    It is interesting …I like it so much:-)

    But as others commented , it is difficult to understand it from the song….

  5. Rame says:

    Could you please send me a diagram of the device to the post office?

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