serialRGB.ino

#define Blue 9
#define Green 10
#define Red 11
#define DelayTime 5
byte blueLast = 0;
byte greenLast = 0;
byte redLast = 0;


void setup() {
  // put your setup code here, to run once:
  pinMode(Blue, OUTPUT);
  pinMode(Green, OUTPUT);
  pinMode(Red, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  byte brightness;
  byte color;
  if(Serial.available()){
    color = Serial.read();
    while(Serial.available() == 0){}
    brightness = Serial.read();
    if(color == 'A'){ fade(Blue, brightness); }
    if(color == 'B'){ fade(Green, brightness); }
    if(color == 'C'){ fade(Red, brightness); }
  }
}

void fade(int color, byte brightness){
  switch(color){
    case Blue:
      changeBrightness(Blue, brightness, blueLast);
      blueLast = brightness;
      break;
    case Green:
      changeBrightness(Green, brightness, greenLast);
      greenLast = brightness;
      break;
    case Red:
      changeBrightness(Red, brightness, redLast);
      redLast = brightness;
      break;
    default:
    break;
  }
}

void changeBrightness(int color, byte brightness, byte lastBrightness){
  if(brightness >= lastBrightness){ //Turn up the brightness
    for(int i = lastBrightness; i <= brightness; i++){
      analogWrite(color, i);
      delay(DelayTime);
    }
  }
  else{ //Turn Down the brightness. What else is there to do?
    for(int i = lastBrightness; i >= brightness; i--){
      analogWrite(color, i);
      delay(DelayTime);
    }
  }
}

systemMonitor.py

#!/usr/bin/env python

import psutil
import serial
import time


# Variables
baud = 9600
port = '/dev/ttyACM0'
ser = serial.Serial(port, baud)

try:
  while 1:
    cpuUsage = psutil.cpu_percent(interval = 1) # Sample CPU usage for ~1 second.
    data = ord('C').to_bytes(1, byteorder='big') # For some reason I can't call #to_bytes on characters directly.
    #print(data) # Debugging
    ser.write(data)
    data = int((cpuUsage / 100) * 255).to_bytes(1, byteorder='big')
    ser.write(data) # Write the data. The conversion steps above are because I do everything in bytes on the
                    # Arduino side. They're not strictly necessary, as the Arduino has character classes.
    time.sleep(0.1)
    
except KeyboardInterrupt:
  print("\nCtrl-C detected. Stopping!")
  
finally:
  # Do some cleanup...
  ser.close()