Arduino 8Ch PPM Decoder with Smoothing and Connection Status

arduinoPPM.ino

unsigned long int ft, lt, x, tfail;
int ch, chx[9][13];

const int idx   = 10;
const int total = 11;
const int val   = 12;

void setup() {
  Serial.begin(9600);
  ft=0; lt=0; x=0; tfail=0; ch=0;
  for (int i=0; i<9; i++) {
    for (int j=0; j<13; j++) {
      chx[i][j]=0;
    }
  }
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), decodePPM, FALLING);
}

void loop() {
  if ((millis()-tfail)>500) {
    Serial.println("Disconnect");
  } else {
    Serial.print(chx[0][val]);Serial.print("\t");
    Serial.print(chx[1][val]);Serial.print("\t");
    Serial.print(chx[2][val]);Serial.print("\t");
    Serial.print(chx[3][val]);Serial.print("\t");
    Serial.print(chx[4][val]);Serial.print("\t"); 
    Serial.print(chx[5][val]);Serial.print("\t");
    Serial.print(chx[6][val]);Serial.print("\t");
    Serial.print(chx[7][val]);Serial.print("\t");
    Serial.println(chx[8][val]);    
  }
}

void decodePPM() {  
  lt    = micros();
  tfail = millis();
  x     = lt-ft;
  ft    = lt;
  if (x>3000) {
    ch          = 0;
    chx[0][val] = x;
  } else {
    ch+=1;
    int indx       = chx[ch][idx];
    chx[ch][total] = chx[ch][total] - chx[ch][indx];
    chx[ch][indx]  = x;
    chx[ch][total] = chx[ch][total] + chx[ch][indx];
    chx[ch][idx]   = chx[ch][idx] + 1;
    if (chx[ch][idx]>9) {
      chx[ch][idx] = 0;
    }
    chx[ch][val] = chx[ch][total]/10;
  }
}