Update README.md

Author: stnkl

README.md

@@ -15,6 +15,7 @@ FastLEDHub allows you to manage all of your [FastLED]([FastLED](https://github.c
 - Alarm: Be woken up to an animation slowly fading in
 - Sunset: Automatically fade in an animation when the sun sets at your location
 - Control animations and brightness using hardware inputs
+- Incorporate audio spectrum data into your animations
 - Control animations using HTTP requests for easy automation
 
 ## Demo
@@ -217,6 +218,17 @@ Setting up an alarm in the web interface will fade in a user defined animation o
 
 Similarly the sunset feature will fade in an animation as soon as the sun sets at your location. Please configure latitude, longitude and time zone in the web interface beforehand.
 
+### Audio spectrum data
+
+[FastLEDHub-AudioViz](https://github.com/stnkl/FastLEDHub_AudioViz) allows you to send audio spectrum data from a Windows audio device to your ESP32/ESP8266. The transmitted data consists of 16 bins corresponding to different frequency ranges in the audio spectrum. Data is transmitted via a websocket connection and can be used by accessing the `FastLEDHub.spectrumData` array from within your animation:
+
+```cpp
+uint8_t lowFrequencies = FastLEDHub.spectrumData[0];
+uint8_t highFrequencies = FastLEDHub.spectrumData[SPECTRUM_LENGTH - 1];
+```
+
+`SPECTRUM_LENGTH` defines the number of bins (16). The `Spectrogram` example shows one way to use the spectrum data in your animations.
+
 ### Control via HTTP requests
 
 Most functions can be triggered via HTTP requests: