Checking Basic Lift - using Single Channels

Checking all connections in Flight Controller board "ok" on board using simple Sketch

Channel 3 (Throttle) is used for checking the functionality.

/*
  Author : Kunchala Anil
  email : anilkunchalaece@gmail.com
  Date : 14 Mar 2018

  Checking the altitude of KSRM Quad


*/
/*
   Connect Channel 3 to pin 10 i.e PCINT2
   Arm the all the Motors
   use Servo Write to Send the control signal to ESC

        To Arm ESC use value 60
        Max Speed Can be Achieved using 130

        Pulse Width when Throttle at Minimum position is : 1150
        Pulse width when Throttle at Maximum Posistion is : 1800

        we need to map value from 1200-1800 to 60 to 130
*/


//PCMSKx - Pin Change Mask Register
//PCMSK0 - portB (D8-D13) (PCINT0  - PCINT6)
//PCMSK1 - portC (A0-A5)  (PCINT8  - PCINT14)
//PCMSK2 - portD (D0-D7)  (PCINT16 - PCINT23)
//PCICR -  Pin Change Interrupt Control Register
//  PCIE0 - Pin Change Interrupt Enable 0 - Port B (D8-D13)
//  PCIE1 - Pin Change Interrupt Enable 1 - Port C (A0-A5)
//  PCIE2 - Pin Change Interrupt Enable 2 - Port D (D0-D7)

#include<Servo.h>

#define rxPin 10
#define DEBUG

//MotorConnections

#define topLeftMotorPin 4
#define topRightMotorPin 5
#define bottomLeftMotorPin 6
#define bottomRightMotorPin 7

#define motorArmValue 60
#define motorMinValue 65
#define motorMaxValue 130

#define throttleMinValue 1200
#define throttleMaxValue 1800

volatile boolean recvPCInt = false;
volatile byte portValue;
unsigned long pwmDuration;
unsigned long pwmStart;
unsigned long pwmEnd;

Servo topLeftMotor;
Servo topRightMotor;
Servo bottomLeftMotor;
Servo bottomRightMotor;

//Interrupt Service Routine will fire when for PinChange in PortB
ISR(PCINT0_vect) {
  recvPCInt = true;
  portValue = PINB; //PINB is used to read all port input values
}

void updateMotors(int val) {
  topLeftMotor.write(val);
  topRightMotor.write(val);
  bottomLeftMotor.write(val);
  bottomRightMotor.write(val);
#ifdef DEBUG
  Serial.print("motors are updated with value => ");
  Serial.println(val);
#endif
}


void initializeMotors() {
  topLeftMotor.attach(topLeftMotorPin);
  topRightMotor.attach(topRightMotorPin);
  bottomLeftMotor.attach(bottomLeftMotorPin);
  bottomRightMotor.attach(bottomRightMotorPin);
#ifdef DEBUG
  Serial.println("motors initialized");
#endif
}//end of initializeMotorsFunction


void armAllMotors() {
  topLeftMotor.write(motorArmValue);
  topRightMotor.write(motorArmValue);
  bottomLeftMotor.write(motorArmValue);
  bottomRightMotor.write(motorArmValue);
#ifdef DEBUG
  Serial.println("motors are Armed ");
#endif
}//end of armAllMotors function



void setup() {
  cli(); //Clear all interrupts
  PCICR |= 1 << PCIE0; //Enable port B Registers i.e D8-D13
  PCMSK0 |= 1 << PCINT2;// Pin9
  sei(); //enable all interrupts
  pinMode(rxPin, INPUT);
  digitalWrite(rxPin, HIGH); //enable pull up in pin
#ifdef DEBUG
  Serial.begin(9600);
#endif
  initializeMotors();
  armAllMotors();
}//end of setup

void loop() {
  if (recvPCInt == true) {
    boolean event = digitalRead(rxPin);
    if (event == HIGH)
    {
      pwmStart = micros();
    }
    else if (event == LOW) {
      pwmEnd = micros();
      int width = pwmEnd - pwmStart;

      int mappedValue = map(width, throttleMinValue, throttleMaxValue, motorMinValue, motorMaxValue);

       updateMotors(mappedValue);

#ifdef DEBUG
      Serial.print("Throttle Value is  ");
      Serial.println(pwmEnd - pwmStart);
#endif
    }
    recvPCInt = false;
  }//end of If

}//end of loop

Multi Channel Receiver Signals using Pin Change Interrupts - Reading Four Channels Simultaneously

The main Logic is :
1.Calculate PWM Starting Value during Raising Edge
 2.When Falling Edge Detected Calculate Width

/*
   Author : Kunchala Anil
   Email : anilkunchlaece@gmail.com
   Date : 6 Mar 2018
   Pin Change Interrupts - Single Rx Channel i.e Single PWM Wave
  PCMSKx - Pin Change Mask Register
  PCMSK0 - portB (D8-D13) (PCINT0  - PCINT6)
  PCMSK1 - portC (A0-A5)  (PCINT8  - PCINT14)
  PCMSK2 - portD (D0-D7)  (PCINT16 - PCINT23)
  PCICR -  Pin Change Interrupt Control Register
    PCIE0 - Pin Change Interrupt Enable 0 - Port B (D8-D13)
    PCIE1 - Pin Change Interrupt Enable 1 - Port C (A0-A5)
    PCIE2 - Pin Change Interrupt Enable 2 - Port D (D0-D7)
*/

/*#############################
  Rx Connections
  Ch1 = D8 PCINT0
  Ch2 = D9 PCINT1
  Ch3 = D10 PCINT2
  Ch4 = D11 PCINT3
*/
#define DEBUG // comment it out to disable the debug mode

volatile boolean recvPCInt = false; //to know interrupt status
volatile int portValue;

//used to store the pwm duration
volatile unsigned long pwmDuration[4];
volatile unsigned long pwmStart[4];
unsigned long pwmEnd[4];

//pinDeclaration for Rx
const byte rxCh[] = {8, 9, 10, 11};
const byte noOfChannels = sizeof(rxCh);

//portStatus
volatile int prevPortState[] = {0, 0, 0, 0};
volatile int presentPortState[4];

//Interrupt Service Routine will fire when for PinChange in PortB
ISR(PCINT0_vect) {
  recvPCInt = true;
  for (int ch = 0; ch < noOfChannels ; ch++) {
    presentPortState[ch] = digitalRead(rxCh[ch]);
  }//end of for loop

  for (int c = 0; c < noOfChannels ; c++) {
    if (prevPortState[c] == 0 & presentPortState[c] == 1) {
      //if previous state is 0 and present state is 1 (Raising Edge) then take the time stamp
      pwmStart[c] = micros();
      prevPortState[c] = 1; //update the prevPort State
    } else if (prevPortState[c] == 1 & presentPortState[c] == 0) {
      //if previous state is 1 and present state is 0 (Falling Edge) then calculate the width based on the change
      pwmDuration[c] = micros() - pwmStart[c];
      prevPortState[c] = 0; //update Present PortState
    }
  }//end of for loop
  //portValue = PINB & 0x0f;//we are only intrested in first four bits
}

void setup() {
  cli(); //Clear all interrupts
  PCICR |= 1 << PCIE0; //Enable port B Registers i.e D8-D13
  PCMSK0 |= (1 << PCINT0) | (1 << PCINT1) | (1 << PCINT2) | (1 << PCINT3);// Pin8,9,10,11
  sei(); //enable all interrupts

#ifdef DEBUG
  Serial.begin(9600);
  Serial.println("DEBUG mode Enabled");
#endif

  for (int ch = 0 ; ch < noOfChannels; ch++) {
    pinMode(rxCh[ch], INPUT_PULLUP); //make pin input with pullup enabled
  }//end of for loop

}//end of setup

void checkForRxPulseWidths() {
  for (int i = 0; i < noOfChannels ; i++ ) {
#ifdef DEBUG
    Serial.print("ch => ");
    Serial.print(i);
    Serial.print(" pulseWidth ");
    Serial.println(pwmDuration[i]);
#endif
  }
}

void loop() {
  if (recvPCInt == true) {
    checkForRxPulseWidths();
    recvPCInt = false;
  }//end of if
}//end of loop

Reading PWM Signals using Pin Change Interrupts

To Measure a PWM wave using Arduino we can follow any one of following ways

1.  built-in pulseIn function
2. Timer and External Interrupts
3. Pin Change Interrupts

Below Code is used to measure PWM width when connected to pin 9

//   Pin Change Interrupts
//PCMSKx - Pin Change Mask Register
//PCMSK0 - portB (D8-D13) (PCINT0  - PCINT6)
//PCMSK1 - portC (A0-A5)  (PCINT8  - PCINT14)
//PCMSK2 - portD (D0-D7)  (PCINT16 - PCINT23)
//PCICR -  Pin Change Interrupt Control Register
//  PCIE0 - Pin Change Interrupt Enable 0 - Port B (D8-D13)
//  PCIE1 - Pin Change Interrupt Enable 1 - Port C (A0-A5)
//  PCIE2 - Pin Change Interrupt Enable 2 - Port D (D0-D7)

volatile boolean recvPCInt = false;
volatile byte portValue;
unsigned long pwmDuration;
unsigned long pwmStart;
unsigned long pwmEnd;


//Interrupt Service Routine will fire when for PinChange in PortB
ISR(PCINT0_vect){
  recvPCInt = true;
  portValue = PINB; //PINB is used to read all port input values
}

void setup() {
cli(); //Clear all interrupts
PCICR |= 1 << PCIE0; //Enable port B Registers i.e D8-D13
PCMSK0 |= 1 << PCINT1;// Pin9
sei(); //enable all interrupts
pinMode(9,INPUT);
digitalWrite(9,HIGH);//enable pull up in pin 9
Serial.begin(9600);
}

void loop() {
  if(recvPCInt == true){
     boolean event = digitalRead(9);
     if(event == HIGH)
        {
          pwmStart = micros();
        }
       else if(event == LOW){
          pwmEnd = micros();
        Serial.println(pwmEnd-pwmStart);
       }
     recvPCInt = false;
  }
}