spectrumLED

spectrumLED is a simple spectrum analyzer meant to be used with a 32x8 LED matrix (MAX7219). Though it can be easily modified to fit the other sizes and matrices.

Build setup

• Hardware:

  • Orange Pi PC (or Raspberry PI)
  • PCM5102 DAC (or any other soundcard)

• Software:

  • Armbian (or Raspbian)
  • Python 3 and third-party packages:
    • numpy
    • scipy
    • luma.core
    • luma.led_matrix
    • pyaudio
  • ALSA

Wiring

1. LED matrix:

LED pin	OPi pin (phys)	OPi pin name
VCC	pin 4	+5V
GND	pin 25	GND
DIN	pin 19	SPI0_MOSI
CS	pin 24	SPI0_CS0
CLK	pin 23	SPI0_CLK

2. PCM5102 DAC (optional):

DAC pin	OPi pin (phys)	OPi pin name
BCK	pin 27	PCM0_CLK
DATA	pin 37	PCM0_DOUT
LRCK	pin 28	PCM0_SYNC
GND	pin 34	GND
GND	pin 39	GND
VCC	pin 2	+5V

Configuration

1. Load a loopback kernel module with:

modprobe snd-aloop

2. Configure ALSA to output multiple streams with multi plugin. Example configuration is listed in asound.conf file: hw:1,0 is a normal soundcard, hw:3,0 is a loopback output, hw:3,1 is a loopback input. Just copy it with:

cp asound.conf /etc/

Change these settings if needed: run aplay -l to list all devices and correct card and device indices in the configuration file.

3. Enable SPI and PCM devices in FEX (legacy kernel) file or add certain overlays (mainline). This is an optional step and depends on your hardware setup. See Armbian site for details.

4. Configure an audio player. If you are using cmus, refer to cmus.rc file. I had no sound when default was specified in dsp.alsa.device option. Though out wrapper works fine.

5. Play some music and run the script:

python3 spectrumLED.py

Real-world examples

Beto Sanchez: 1 and 2