PPM to PWM Conversion Program for Arduino Pro Mini

PWMtoPPM.ino

/*
 * 2019 Boraini.
 * 
 * All permissions are hereby granted to the end user. Use at your own risk.
 */

//pin definitions. Using pin 2 is mandatory since it is the hardware interrupt pin of Pro Mini.
#define RX_PIN 2
#define OUT_PIN 9
#define ENABLE_PIN 13

//RX pulse separation in microseconds
#define MINSIGNAL 1000
#define MAXSIGNAL 2000

//interval between motor output updates
#define UPDATE_INTERVAL 100

//volatile declarations are necessary to be able to manipulate the values during an interrupt.
unsigned volatile long  sigStart; //32 bits
unsigned volatile short sig;      //16 bits
bool                    bin;      //Logical

void setup() {
  //RX reading is available in serial for convenience.
  Serial.begin(9600);
  
  pinMode(RX_PIN, INPUT);
  pinMode(ENABLE_PIN, OUTPUT);
  pinMode(OUT_PIN, OUTPUT);

  //enable L298N
  digitalWrite(ENABLE_PIN, HIGH);

  //we detect both the rising and falling edges of the RX signal
  attachInterrupt(digitalPinToInterrupt(RX_PIN), calcThrottle, CHANGE);
}

//this somehow works
void calcThrottle() {
  if (digitalRead(RX_PIN))
  {
    //begin counting
    sigStart = micros();
  }
  else
  {
    //end counting
    sig = (micros() - sigStart);
  }
}

void loop() {
  //we disable interrupts "just in case"
  noInterrupts();
  analogWrite(OUT_PIN, map(sig, MINSIGNAL, MAXSIGNAL, 0, 255));
  interrupts();

  //this doesn't block the readings since we use interrupts. Yay!
  delay(UPDATE_INTERVAL);
}