ardupilot/Arducopter/Arducopter.pde

/* ********************************************************************** */
/* j                   ArduCopter Quadcopter code                          */
/*                                                                        */
/* Quadcopter code from AeroQuad project and ArduIMU quadcopter project   */
/* IMU DCM code from Diydrones.com                                        */
/* (Original ArduIMU code from Jordi Muñoz and William Premerlani)        */
/* Ardupilot core code : from DIYDrones.com development team              */
/* Authors : Arducopter development team                                  */
/*           Ted Carancho (aeroquad), Jose Julio, Jordi Muñoz,            */
/*           Jani Hirvinen, Ken McEwans, Roberto Navoni,                  */
/*           Sandro Benigno, Chris Anderson                               */
/* Date : 08-08-2010                                                      */
/* Version : 1.3 beta                                                     */
/* Hardware : ArduPilot Mega + Sensor Shield (Production versions)        */
/* Mounting position : RC connectors pointing backwards                   */
/* This code use this libraries :                                         */
/*   APM_RC : Radio library (with InstantPWM)                             */
/*   APM_ADC : External ADC library                                       */
/*   DataFlash : DataFlash log library                                    */
/*   APM_BMP085 : BMP085 barometer library                                */
/*   APM_Compass : HMC5843 compass library [optional]                     */
/*   GPS_UBLOX or GPS_NMEA or GPS_MTK : GPS library    [optional]         */
/* ********************************************************************** */

/*
**** Switch Functions *****
 AUX1 ON = Stable Mode
 AUX1 OFF = Acro Mode
 GEAR ON = GPS Hold
 GEAR OFF = Flight Assist (Stable Mode)
 
 **** LED Feedback ****
 Green LED On = APM Initialization Finished
 Yellow LED On = GPS Hold Mode
 Yellow LED Off = Flight Assist Mode (No GPS)
 Red LED On = GPS Fix, 2D or 3D
 Red LED Off = No GPS Fix

 Green LED blink slow = Motors armed, Stable mode
 Green LED blink rapid = Motors armed, Acro mode
 
*/

/* User definable modules */

// Comment out with // modules that you are not using
#define IsGPS    // Do we have a GPS connected
#define IsNEWMTEK// Do we have MTEK with new firmware
#define IsMAG    // Do we have a Magnetometer connected, if have remember to activate it from Configurator
#define IsTEL    // Do we have a telemetry connected, eg. XBee connected on Telemetry port
#define IsAM     // Do we have motormount LED's. AM = Atraction Mode

#define CONFIGURATOR  // Do se use Configurator or normal text output over serial link

/* User definable modules - END */

// Frame build condiguration
#define FLIGHT_MODE_+    // Traditional "one arm as nose" frame configuration
//#define FLIGHT_MODE_X  // Frame orientation 45 deg to CCW, nose between two arms


/* ****************************************************************************** */
/* ****************************** Includes ************************************** */
/* ****************************************************************************** */

#include <Wire.h>
#include <APM_ADC.h>
#include <APM_RC.h>
#include <DataFlash.h>
#include <APM_Compass.h>

//#include <GPS_NMEA.h>   // General NMEA GPS 
#include <GPS_MTK.h>      // MediaTEK DIY Drones GPS. 
//#include <GPS_UBLOX.h>  // uBlox GPS

// EEPROM storage for user configurable values
#include <EEPROM.h>
#include "ArduCopter.h"
#include "UserConfig.h"

#define SWVER 1.31    // Current software version (only numeric values)


/* ***************************************************************************** */
/* ************************ CONFIGURATION PART ********************************* */
/* ***************************************************************************** */

// Normal users does not need to edit anything below these lines. If you have
// need, go and change them in FrameConfig.h

/* ************************************************************ */
/* Altitude control... (based on sonar) */
void Altitude_control(int target_sonar_altitude)
{
  err_altitude_old = err_altitude;
  err_altitude = target_sonar_altitude - Sonar_value;  
  altitude_D = (float)(err_altitude - err_altitude_old) / G_Dt;
  altitude_I += (float)err_altitude * G_Dt;
  altitude_I = constrain(altitude_I, -100, 100);
  command_altitude = Initial_Throttle + KP_ALTITUDE * err_altitude + KD_ALTITUDE * altitude_D + KI_ALTITUDE * altitude_I;
}

/* ************************************************************ */
/* Position control... */
void Position_control(long lat_dest, long lon_dest)
{
  long Lon_diff;
  long Lat_diff;
  float gps_err_roll;
  float gps_err_pitch;

  Lon_diff = lon_dest - GPS.Longitude;
  Lat_diff = lat_dest - GPS.Lattitude;

  // ROLL
  gps_err_roll_old = gps_err_roll;
  //Optimization : cos(yaw) = DCM_Matrix[0][0] ;  sin(yaw) = DCM_Matrix[1][0] 
  gps_err_roll = (float)Lon_diff*GEOG_CORRECTION_FACTOR*DCM_Matrix[0][0] - (float)Lat_diff*DCM_Matrix[1][0];

  gps_roll_D = (gps_err_roll-gps_err_roll_old)/G_Dt;

  gps_roll_I += gps_err_roll*G_Dt;
  gps_roll_I = constrain(gps_roll_I,-500,500);

  command_gps_roll = KP_GPS_ROLL*gps_err_roll + KD_GPS_ROLL*gps_roll_D + KI_GPS_ROLL*gps_roll_I;
  command_gps_roll = constrain(command_gps_roll,-GPS_MAX_ANGLE,GPS_MAX_ANGLE); // Limit max command

  // PITCH
  gps_err_pitch_old = gps_err_pitch;
  gps_err_pitch = -(float)Lat_diff*DCM_Matrix[0][0]- (float)Lon_diff*GEOG_CORRECTION_FACTOR*DCM_Matrix[1][0];

  gps_pitch_D = (gps_err_pitch-gps_err_pitch_old)/G_Dt;

  gps_pitch_I += gps_err_pitch*G_Dt;
  gps_pitch_I = constrain(gps_pitch_I,-500,500);

  command_gps_pitch = KP_GPS_PITCH*gps_err_pitch + KD_GPS_PITCH*gps_pitch_D + KI_GPS_PITCH*gps_pitch_I;
  command_gps_pitch = constrain(command_gps_pitch,-GPS_MAX_ANGLE,GPS_MAX_ANGLE); // Limit max command
}



/* ************************************************************ */
// STABLE MODE
// ROLL, PITCH and YAW PID controls... 
// Input : desired Roll, Pitch and Yaw absolute angles. Output : Motor commands
void Attitude_control_v2()
{
  float err_roll_rate;
  float err_pitch_rate;
  float roll_rate;
  float pitch_rate;

  // ROLL CONTROL    
  if (AP_mode == 2)        // Normal Mode => Stabilization mode
    err_roll = command_rx_roll - ToDeg(roll);
  else
    err_roll = (command_rx_roll + command_gps_roll) - ToDeg(roll);  // Position control

    err_roll = constrain(err_roll, -25, 25);  // to limit max roll command...

  // New control term...
  roll_rate = ToDeg(Omega[0]);  // Omega[] is the raw gyro reading plus Omega_I, so it´s bias corrected
  err_roll_rate = ((ch_roll - roll_mid) >> 1) - roll_rate;

  roll_I += err_roll * G_Dt;
  roll_I = constrain(roll_I, -20, 20);
  // D term implementation => two parts: gyro part and command part
  // To have a better (faster) response we can use the Gyro reading directly for the Derivative term...
  // We also add a part that takes into account the command from user (stick) to make the system more responsive to user inputs
  roll_D = - roll_rate;  // Take into account Angular velocity of the stick (command)

  // PID control
  K_aux = KP_QUAD_ROLL; // Comment this out if you want to use transmitter to adjust gain
  control_roll = K_aux * err_roll + KD_QUAD_ROLL * roll_D + KI_QUAD_ROLL * roll_I + STABLE_MODE_KP_RATE * err_roll_rate;  

  // PITCH CONTROL
  if (AP_mode==2)        // Normal mode => Stabilization mode
    err_pitch = command_rx_pitch - ToDeg(pitch);
  else
    err_pitch = (command_rx_pitch + command_gps_pitch) - ToDeg(pitch);  // Position Control

  err_pitch = constrain(err_pitch,-25,25);  // to limit max pitch command...

  // New control term...
  pitch_rate = ToDeg(Omega[1]);
  err_pitch_rate = ((ch_pitch - pitch_mid) >> 1) - pitch_rate;

  pitch_I += err_pitch*G_Dt;
  pitch_I = constrain(pitch_I,-20,20);
  // D term
  pitch_D = - pitch_rate;

  // PID control
  K_aux = KP_QUAD_PITCH; // Comment this out if you want to use transmitter to adjust gain
  control_pitch = K_aux * err_pitch + KD_QUAD_PITCH * pitch_D + KI_QUAD_PITCH * pitch_I + STABLE_MODE_KP_RATE * err_pitch_rate; 

  // YAW CONTROL
  err_yaw = command_rx_yaw - ToDeg(yaw);
  if (err_yaw > 180)    // Normalize to -180,180
      err_yaw -= 360;
  else if(err_yaw < -180)
    err_yaw += 360;

  err_yaw = constrain(err_yaw, -60, 60);  // to limit max yaw command...

  yaw_I += err_yaw * G_Dt;
  yaw_I = constrain(yaw_I, -20, 20);
  yaw_D = - ToDeg(Omega[2]);

  // PID control
  control_yaw = KP_QUAD_YAW * err_yaw + KD_QUAD_YAW * yaw_D + KI_QUAD_YAW * yaw_I;
}

// ACRO MODE
void Rate_control()
{
  static float previousRollRate, previousPitchRate, previousYawRate;
  float currentRollRate, currentPitchRate, currentYawRate;

  // ROLL CONTROL
  currentRollRate = read_adc(0);      // I need a positive sign here

  err_roll = ((ch_roll - roll_mid) * xmitFactor) - currentRollRate;

  roll_I += err_roll * G_Dt;
  roll_I = constrain(roll_I, -20, 20);

  roll_D = currentRollRate - previousRollRate;
  previousRollRate = currentRollRate;

  // PID control
  control_roll = Kp_RateRoll * err_roll + Kd_RateRoll * roll_D + Ki_RateRoll * roll_I; 

  // PITCH CONTROL
  currentPitchRate = read_adc(1);
  err_pitch = ((ch_pitch - pitch_mid) * xmitFactor) - currentPitchRate;

  pitch_I += err_pitch*G_Dt;
  pitch_I = constrain(pitch_I,-20,20);

  pitch_D = currentPitchRate - previousPitchRate;
  previousPitchRate = currentPitchRate;

  // PID control
  control_pitch = Kp_RatePitch*err_pitch + Kd_RatePitch*pitch_D + Ki_RatePitch*pitch_I; 

  // YAW CONTROL
  currentYawRate = read_adc(2);
  err_yaw = ((ch_yaw - yaw_mid) * xmitFactor) - currentYawRate;

  yaw_I += err_yaw*G_Dt;
  yaw_I = constrain(yaw_I,-20,20);

  yaw_D = currentYawRate - previousYawRate;
  previousYawRate = currentYawRate;

  // PID control
  K_aux = KP_QUAD_YAW; // Comment this out if you want to use transmitter to adjust gain
  control_yaw = Kp_RateYaw*err_yaw + Kd_RateYaw*yaw_D + Ki_RateYaw*yaw_I; 
}

// Maximun slope filter for radio inputs... (limit max differences between readings)
int channel_filter(int ch, int ch_old)
{
  int diff_ch_old;

  if (ch_old==0)      // ch_old not initialized
    return(ch);
  diff_ch_old = ch - ch_old;      // Difference with old reading
  if (diff_ch_old<0)
  {
    if (diff_ch_old<-40)
      return(ch_old-40);        // We limit the max difference between readings
  }
  else
  {
    if (diff_ch_old>40)    
      return(ch_old+40);
  }
  return((ch + ch_old) >> 1);   // Small filtering
  //return(ch);
}

/* ************************************************************ */
/* **************** MAIN PROGRAM - SETUP ********************** */
/* ************************************************************ */
void setup()
{
  int i;
  float aux_float[3];

  pinMode(LED_Yellow,OUTPUT); //Yellow LED A  (PC1)
  pinMode(LED_Red,OUTPUT);    //Red LED B     (PC2)
  pinMode(LED_Green,OUTPUT);  //Green LED C   (PC0)

  pinMode(SW1_pin,INPUT);     //Switch SW1 (pin PG0)

  pinMode(RELE_pin,OUTPUT);   // Rele output
  digitalWrite(RELE_pin,LOW);

  delay(1000); // Wait until frame is not moving after initial power cord has connected

  APM_RC.Init();             // APM Radio initialization
  APM_ADC.Init();            // APM ADC library initialization
  DataFlash.Init();          // DataFlash log initialization

#ifdef IsGPS  
  GPS.Init();                // GPS Initialization
#ifdef IsNEWMTEK  
  delay(250);
  // DIY Drones MTEK GPS needs binary sentences activated if you upgraded to latest firmware.
  // If your GPS shows solid blue but LED C (Red) does not go on, your GPS is on NMEA mode
  Serial1.print("$PGCMD,16,0,0,0,0,0*6A\r\n"); 
#endif
#endif

  readUserConfig(); // Load user configurable items from EEPROM
  
  // Safety measure for Channel mids
  if(roll_mid < 1400 || roll_mid > 1600) roll_mid = 1500;
  if(pitch_mid < 1400 || pitch_mid > 1600) pitch_mid = 1500;
  if(yaw_mid < 1400 || yaw_mid > 1600) yaw_mid = 1500;


  // RC channels Initialization (Quad motors)  
  APM_RC.OutputCh(0,MIN_THROTTLE);  // Motors stoped
  APM_RC.OutputCh(1,MIN_THROTTLE);
  APM_RC.OutputCh(2,MIN_THROTTLE);
  APM_RC.OutputCh(3,MIN_THROTTLE);

  if (MAGNETOMETER == 1)
    APM_Compass.Init();  // I2C initialization

  DataFlash.StartWrite(1);   // Start a write session on page 1

    //Serial.begin(57600);
  Serial.begin(115200);
  //Serial.println();
  //Serial.println("ArduCopter Quadcopter v1.0");

  // Check if we enable the DataFlash log Read Mode (switch)
  // If we press switch 1 at startup we read the Dataflash eeprom
  while (digitalRead(SW1_pin)==0)
  {
    Serial.println("Entering Log Read Mode...");
    Log_Read(1,1000);
    delay(30000);
  }

  Read_adc_raw();
  delay(20);

  // Offset values for accels and gyros...
  AN_OFFSET[3] = acc_offset_x;
  AN_OFFSET[4] = acc_offset_y;
  AN_OFFSET[5] = acc_offset_z;
  aux_float[0] = gyro_offset_roll;
  aux_float[1] = gyro_offset_pitch;
  aux_float[2] = gyro_offset_yaw;

  // Take the gyro offset values
  for(i=0;i<300;i++)
  {
    Read_adc_raw();
    for(int y=0; y<=2; y++)   // Read initial ADC values for gyro offset.
    {
      aux_float[y]=aux_float[y]*0.8 + AN[y]*0.2;
      //Serial.print(AN[y]);
      //Serial.print(",");
    }
    //Serial.println();
    Log_Write_Sensor(AN[0],AN[1],AN[2],AN[3],AN[4],AN[5],ch_throttle);
    delay(10);
  }
  for(int y=0; y<=2; y++)   
    AN_OFFSET[y]=aux_float[y];

//  Neutro_yaw = APM_RC.InputCh(3); // Take yaw neutral radio value
#ifndef CONFIGURATOR
  for(i=0;i<6;i++)
  {
    Serial.print("AN[]:");
    Serial.println(AN_OFFSET[i]);
  }

  Serial.print("Yaw neutral value:");
//  Serial.println(Neutro_yaw);
  Serial.print(yaw_mid);
#endif

#ifdef RADIO_TEST_MODE    // RADIO TEST MODE TO TEST RADIO CHANNELS
  while(1)
  {
    if (APM_RC.GetState()==1)
    {
      Serial.print("AIL:");
      Serial.print(APM_RC.InputCh(0));
      Serial.print("ELE:");
      Serial.print(APM_RC.InputCh(1));
      Serial.print("THR:");
      Serial.print(APM_RC.InputCh(2));
      Serial.print("YAW:");
      Serial.print(APM_RC.InputCh(3));
      Serial.print("AUX(mode):");
      Serial.print(APM_RC.InputCh(4));
      Serial.print("AUX2:");
      Serial.print(APM_RC.InputCh(5));
      Serial.println();
      delay(200);
    }
  } 
#endif  

  delay(1000);

  DataFlash.StartWrite(1);   // Start a write session on page 1
  timer = millis();
  tlmTimer = millis();
  Read_adc_raw();        // Initialize ADC readings...
  delay(20);
  
    // Switch Left & Right lights on
  digitalWrite(RI_LED, HIGH);
  digitalWrite(LE_LED, HIGH); 
  
  motorArmed = 0;
  digitalWrite(LED_Green,HIGH);     // Ready to go...
}


/* ************************************************************ */
/* ************** MAIN PROGRAM - MAIN LOOP ******************** */
/* ************************************************************ */
void loop(){

  int aux;
  int i;
  float aux_float;
  //Log variables
  int log_roll;
  int log_pitch;
  int log_yaw;


  if((millis()-timer)>=10)   // Main loop 100Hz
  {
    counter++;
    timer_old = timer;
    timer=millis();
    G_Dt = (timer-timer_old)/1000.0;      // Real time of loop run 

    // IMU DCM Algorithm
    Read_adc_raw();
#ifdef IsMAG
    if (MAGNETOMETER == 1) {
      if (counter > 10)  // Read compass data at 10Hz... (10 loop runs)
      {
        counter=0;
        APM_Compass.Read();     // Read magnetometer
        APM_Compass.Calculate(roll,pitch);  // Calculate heading
      }
    }
#endif    
    Matrix_update(); 
    Normalize();
    Drift_correction();
    Euler_angles();
    // *****************

    // Output data
    log_roll = ToDeg(roll) * 10;
    log_pitch = ToDeg(pitch) * 10;
    log_yaw = ToDeg(yaw) * 10;

#ifndef CONFIGURATOR    
    Serial.print(log_roll);
    Serial.print(",");
    Serial.print(log_pitch);
    Serial.print(",");
    Serial.print(log_yaw);

    for (int i=0;i<6;i++)
    {
      Serial.print(AN[i]);
      Serial.print(",");
    }
#endif

    // Write Sensor raw data to DataFlash log
    Log_Write_Sensor(AN[0],AN[1],AN[2],AN[3],AN[4],AN[5],gyro_temp);
    // Write attitude to DataFlash log
    Log_Write_Attitude(log_roll,log_pitch,log_yaw);

    if (APM_RC.GetState()==1)   // New radio frame?
    {
      // Commands from radio Rx... 
      // Stick position defines the desired angle in roll, pitch and yaw
      ch_roll = channel_filter(APM_RC.InputCh(0), ch_roll);
      ch_pitch = channel_filter(APM_RC.InputCh(1), ch_pitch);
      ch_throttle = channel_filter(APM_RC.InputCh(2), ch_throttle);
      ch_yaw = channel_filter(APM_RC.InputCh(3), ch_yaw);
      ch_aux = APM_RC.InputCh(4);
      ch_aux2 = APM_RC.InputCh(5);
      command_rx_roll_old = command_rx_roll;
      command_rx_roll = (ch_roll-CHANN_CENTER) / 12.0;
      command_rx_roll_diff = command_rx_roll - command_rx_roll_old;
      command_rx_pitch_old = command_rx_pitch;
      command_rx_pitch = (ch_pitch-CHANN_CENTER) / 12.0;
      command_rx_pitch_diff = command_rx_pitch - command_rx_pitch_old;
//      aux_float = (ch_yaw-Neutro_yaw) / 180.0;
      aux_float = (ch_yaw-yaw_mid) / 180.0;
      command_rx_yaw += aux_float;
      command_rx_yaw_diff = aux_float;
      if (command_rx_yaw > 180)         // Normalize yaw to -180,180 degrees
        command_rx_yaw -= 360.0;
      else if (command_rx_yaw < -180)
        command_rx_yaw += 360.0;

      // Read through comments in Attitude_control() if you wish to use transmitter to adjust P gains
      // I use K_aux (channel 6) to adjust gains linked to a knob in the radio... [not used now]
      //K_aux = K_aux*0.8 + ((ch_aux-1500)/100.0 + 0.6)*0.2;
      K_aux = K_aux * 0.8 + ((ch_aux2-AUX_MID) / 300.0 + 1.7) * 0.2;   // /300 + 1.0

      if (K_aux < 0)
        K_aux = 0;

      //Serial.print(",");
      //Serial.print(K_aux);

      // We read the Quad Mode from Channel 5
      if (ch_aux < 1200)
      {
        AP_mode = 1;           // Position hold mode (GPS position control)
        digitalWrite(LED_Yellow,HIGH); // Yellow LED On
      }
      else
      {
        AP_mode = 2;          // Normal mode (Stabilization assist mode)
        digitalWrite(LED_Yellow,LOW); // Yellow LED off
      }
      // Write Radio data to DataFlash log
      Log_Write_Radio(ch_roll,ch_pitch,ch_throttle,ch_yaw,int(K_aux*100),(int)AP_mode);
    }  // END new radio data


    if (AP_mode==1)  // Position Control
    {
      if (target_position==0)   // If this is the first time we switch to Position control, actual position is our target position
      {
        target_lattitude = GPS.Lattitude;
        target_longitude = GPS.Longitude;

#ifndef CONFIGURATOR
        Serial.println();
        Serial.print("* Target:");
        Serial.print(target_longitude);
        Serial.print(",");
        Serial.println(target_lattitude);
#endif
        target_position=1;
        //target_sonar_altitude = sonar_value;
        //Initial_Throttle = ch3;
        // Reset I terms
        altitude_I = 0;
        gps_roll_I = 0;
        gps_pitch_I = 0;
      }        
    }
    else
      target_position=0;

    //Read GPS
    GPS.Read();
    if (GPS.NewData)  // New GPS data?
    {
      GPS.NewData=0;  // We Reset the flag...

      //Output GPS data
      //Serial.print(",");
      //Serial.print(GPS.Lattitude);
      //Serial.print(",");
      //Serial.print(GPS.Longitude);

      // Write GPS data to DataFlash log
      Log_Write_GPS(GPS.Time, GPS.Lattitude,GPS.Longitude,GPS.Altitude, GPS.Ground_Speed, GPS.Ground_Course, GPS.Fix, GPS.NumSats);

      if (GPS.Fix >= 2)
        digitalWrite(LED_Red,HIGH);  // GPS Fix => Blue LED
      else
        digitalWrite(LED_Red,LOW);

      if (AP_mode==1)
      {
        if ((target_position==1) && (GPS.Fix))
        {
          Position_control(target_lattitude,target_longitude);  // Call position hold routine
        }
        else
        {
          //Serial.print("NOFIX");
          command_gps_roll=0;
          command_gps_pitch=0;
        }
      }
    }

    // Control methodology selected using AUX2
    if (ch_aux2 < 1200) {
      gled_speed = 1200;
      Attitude_control_v2();
    }
    else
    {
      gled_speed = 400;
      Rate_control();
      // Reset yaw, so if we change to stable mode we continue with the actual yaw direction
      command_rx_yaw = ToDeg(yaw);
      command_rx_yaw_diff = 0;
    }

    // Arm motor output : Throttle down and full yaw right for more than 2 seconds
    if (ch_throttle < 1200) {
      control_yaw = 0;
      command_rx_yaw = ToDeg(yaw);
      command_rx_yaw_diff = 0;
      if (ch_yaw > 1800) {
        if (Arming_counter > ARM_DELAY){
          motorArmed = 1;
          minThrottle = 1100;
        }
        else
          Arming_counter++;
      }
      else
        Arming_counter=0;
      // To Disarm motor output : Throttle down and full yaw left for more than 2 seconds
      if (ch_yaw < 1200) {
        if (Disarming_counter > DISARM_DELAY){
          motorArmed = 0;
          minThrottle = MIN_THROTTLE;
        }
        else
          Disarming_counter++;
      }
      else
        Disarming_counter=0;
    }
    else{
      Arming_counter=0;
      Disarming_counter=0;
    }

    // Quadcopter mix
    // Ask Jose if we still need this IF statement, and if we want to do an ESC calibration
    if (motorArmed == 1) {   
       digitalWrite(FR_LED, HIGH);    // AM-Mode
     
#ifdef FLIGHT_MODE_+
      rightMotor = constrain(ch_throttle - control_roll - control_yaw, minThrottle, 2000);
      leftMotor = constrain(ch_throttle + control_roll - control_yaw, minThrottle, 2000);
      frontMotor = constrain(ch_throttle + control_pitch + control_yaw, minThrottle, 2000);
      backMotor = constrain(ch_throttle - control_pitch + control_yaw, minThrottle, 2000);
#endif
#ifdef FLIGHT_MODE_X
      frontMotor = constrain(ch_throttle + control_roll + control_pitch - control_yaw, minThrottle, 2000); // front left motor
      rightMotor = constrain(ch_throttle - control_roll + control_pitch + control_yaw, minThrottle, 2000); // front right motor
      leftMotor = constrain(ch_throttle + control_roll - control_pitch + control_yaw, minThrottle, 2000);  // rear left motor
      backMotor = constrain(ch_throttle - control_roll - control_pitch - control_yaw, minThrottle, 2000);  // rear right motor
#endif
    }
    if (motorArmed == 0) {
      digitalWrite(FR_LED, LOW);    // AM-Mode
      digitalWrite(LED_Green,HIGH); // Ready LED on
      
      rightMotor = MIN_THROTTLE;
      leftMotor = MIN_THROTTLE;
      frontMotor = MIN_THROTTLE;
      backMotor = MIN_THROTTLE;
      roll_I = 0;     // reset I terms of PID controls
      pitch_I = 0;
      yaw_I = 0; 
      // Initialize yaw command to actual yaw when throttle is down...
      command_rx_yaw = ToDeg(yaw);
      command_rx_yaw_diff = 0;
    }
    APM_RC.OutputCh(0, rightMotor);    // Right motor
    APM_RC.OutputCh(1, leftMotor);    // Left motor
    APM_RC.OutputCh(2, frontMotor);   // Front motor
    APM_RC.OutputCh(3, backMotor);   // Back motor     
    
    // InstantPWM
    APM_RC.Force_Out0_Out1();
    APM_RC.Force_Out2_Out3();

#ifndef CONFIGURATOR
    Serial.println();  // Line END 
#endif
  }
#ifdef CONFIGURATOR
  if((millis()-tlmTimer)>=100) {
    readSerialCommand();
    sendSerialTelemetry();
    tlmTimer = millis();
  }
#endif

  // AM and Mode status LED lights
  if(millis() - gled_timer > gled_speed) {
    gled_timer = millis();
    if(gled_status == HIGH) { 
      digitalWrite(LED_Green, LOW);
#ifdef IsAM      
      digitalWrite(RE_LED, LOW);
#endif
      gled_status = LOW;
    } 
    else {
      digitalWrite(LED_Green, HIGH);
#ifdef IsAM
      if(motorArmed) digitalWrite(RE_LED, HIGH);
#endif
      gled_status = HIGH;
    } 
  }



}