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Dagu Rover 5 remote control with nRF24L01 from Bajdi on Vimeo.

I have updated my sketch to remote control the Rover 5. There were a couple of things I wanted to try out. The Dagu 4 channel motor controller I use is equipped with 4 current outputs. These outputs give a 0 to 5V signal, 5V equals 5A. I hooked up all 4 sensor outputs to 4 analog inputs on the Red back spider. To know how much amps a motor draws the analogread value is divided by 1023 and then multiplied by 5. Another thing I wanted to try was sending back data from the Rover to my remote using the RF24 Arduino library. This is very handy when you’re testing new code. Attaching a USB cable to your Rover while it’s driving around is not very practical. This gave me some trouble, when I originally wrote the sketch I had a lot of serial.print lines in the code and my sketch worked. When I removed these serial.print statements the sketch stopped working. Very strange and it took me a long time to figure out. When I replaced the serial.print statements with a tiny delay the code worked. To make this delay I did not use the delay function, but used the code from the “blink without delay” example sketch. You don’t want to have delay statements in code for a remote controlled vehicle, I tried it and it made my Rover very unresponsive. After getting this to work I attached an I2C LCD to my “remote” so I could print the motor current values to it. I only have had an 2×16 lcd and after printing the 4 values to the lcd there is no more space for other stuff. I’ve just received a 4×20 I2C LCD, cost me 20$ on Ebay. This gives me some more “room” to play with. As you can see in the video my Rover 5 has become a big cable mess, should do something about that

Here is the sketch that I’m using for the remote;

// http://www.bajdi.com
// Nrf24L01 connected to Arduino Uno
// Nrf24L01 connection details http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo
// Transmit analog values from joystick to the receiver using RF24 library
// Receive 4 floats (current from the motors) from Rover 5 motor controller

#include <SPI.h>
#include <nRF24L01.h>
#include "RF24.h"
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Bounce.h>

LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to 0x27

RF24 radio(8,7);

const uint64_t pipes[2] = {
  0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

int joystick[3];
float current[4];

const int z = 2;
int roverState = LOW;         // the current state of the output pin

Bounce bouncer = Bounce( z, 5 );

long previousMillis = 0;
long interval = 25;

void setup(){
  pinMode(z, INPUT);
  radio.begin();
  radio.openWritingPipe(pipes[0]);
  radio.openReadingPipe(1,pipes[1]);
  radio.startListening();

  lcd.init(); // initialize the lcd
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("M1=");
  lcd.setCursor(8,0);
  lcd.print("M2=");
  lcd.setCursor(0,1);
  lcd.print("M3=");
  lcd.setCursor(8,1);
  lcd.print("M4=");

}

void loop(){
  joystick[0] = analogRead(A0);
  joystick[1] = analogRead(A1);
  joystick[2] = roverState;

  if ( bouncer.update() ) {
    if ( bouncer.read() == HIGH) {
      if ( roverState == LOW ) {
        roverState = HIGH;
      }
      else {
        roverState = LOW;
      }
    }
  }

  if ( radio.available() )
  {
    unsigned long currentMillis = millis();

  if(currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;   

    // Dump the payloads until we've gotten everything
    bool done = false;
    while (!done)
    {
      // Fetch the payload, and see if this was the last one.
      done = radio.read( &current, sizeof(current) );

    }
  }

    lcd.setCursor(3,0);
    lcd.print(current[0]);
    lcd.setCursor(11,0);
    lcd.print(current[1]);
    lcd.setCursor(3,1);
    lcd.print(current[2]);
    lcd.setCursor(11,1);
    lcd.print(current[3]);

    radio.stopListening();

    bool ok = radio.write( &joystick, sizeof(joystick) );

    radio.startListening();  

  }
}

This is the sketch that goes in the Red back spider that controls the Rover 5:

// http://www.bajdi.com
// Dagu Rover 5 chassis with 4 motors
// Remote control through Nrf24L01 2,4GHz wireless module
// µcontroller = Dagu Red back spider, Arduino Mega 1280 compatible
// Motor controller = Dagu 4 channel motor controller
// Motor 1 and 2 on the left
// Motor 3 and 4 on the right
// Sent 4 floats (motor current) to transmitter (remote)

#include <SPI.h>
#include <nRF24L01.h>
#include "RF24.h"
#include "Ultrasonic.h"
#include <VarSpeedServo.h>

/* Nrf24L01 pinout
 1 GND
 2 VCC (3,3V)
 3 CE    pin 48 on Mega 1280
 4 CSN   pin 49 on Mega 1280
 5 SCK   pin 52 on Mega 1280
 6 MOSI  pin 51 on Mega 1280
 7 MISO  pin 50 on Mega 1280
 8 IRQ (not used)
 */

RF24 radio(48,49);
const uint64_t pipes[2] = {
  0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

int DirM1 = 30; // direction motor 1
int DirM2 = 31; // direction motor 2
int DirM3 = 32; // direction motor 3
int DirM4 = 33; // direction motor 4
int PWMM1 = 4;  // pwm motor 1
int PWMM2 = 5;  // pwm motor 2
int PWMM3 = 6;  // pwm motor 3
int PWMM4 = 7;  // pwm motor 4

int fs; // forward speed
int bs; // backward speed
int ls; // turn left speed
int rs; // turn right speed

int bat; // analog reading of battery voltage through voltage divider
const int lowbat = 34; // low battery led (red)
const int buzzer = 35; // buzzer
const int orange = 38; // orange leds
const int headlight = 39; // white leds

const int  TRIG = 36;
const int  ECHO = 37;

Ultrasonic SRF6A(TRIG, ECHO);

VarSpeedServo SRF6AServo;        // servo objects

int servoSpeeds = 30; // sweep speed, 1 is slowest, 255 fastest)
int servoMinPosition = 20; // the minumum servo angle
int servoMaxPosition = 110; // the maximum servo angle

int joystick[3];    // Array with 2 analog values (X,Y-axis) and one digital (Z-axis) from transmitter/joystick
float current[4];   // Array with the 4 motor current values, to sent to remote control

int apin[] = {
  A1, A2, A3, A4 };  // analog pin array

long previousMillis = 0;

long interval = 25;

void setup() {
  pinMode(DirM1, OUTPUT);  // direction motor 1, left front
  pinMode(DirM2, OUTPUT);  // direction motor 2, left rear
  pinMode(DirM3, OUTPUT);  // direction motor 3, right front
  pinMode(DirM4, OUTPUT);  // direction motor 4, right rear
  pinMode(PWMM1, OUTPUT);  // PWM motor 1
  pinMode(PWMM2, OUTPUT);  // PWM motor 2
  pinMode(PWMM3, OUTPUT);  // PWM motor 3
  pinMode(PWMM4, OUTPUT);  // PWM motor 4
  pinMode(lowbat, OUTPUT); // low battery led (red)
  pinMode(buzzer, OUTPUT); // buzzer
  pinMode(orange, OUTPUT); // orange leds
  pinMode(headlight, OUTPUT); // white leds

  SRF6AServo.attach(8);
  SRF6AServo.slowmove(servoMinPosition,servoSpeeds) ; // start sweeping from min position

  radio.begin();
  radio.openWritingPipe(pipes[1]);
  radio.openReadingPipe(1,pipes[0]);
  radio.startListening();
}

void loop() {

  bat = analogRead(A0);

  if (bat < 760)       // 760 / 1023 * 5 * 2 = 7,4V from battery
  {
    digitalWrite(lowbat, HIGH);
  }
  else
  {
    digitalWrite(lowbat, LOW);
  }

  if ( radio.available() )
  {
    // Dump the payloads until we've gotten everything
    bool done = false;
    while (!done)
    {
      // Fetch the payload, and see if this was the last one.
      done = radio.read( &joystick, sizeof(joystick) );
    }
    if (bat > 760 && joystick[2] == HIGH)       // 760 / 1023 * 5 * 2 = 7,4V from battery
    {
      digitalWrite(headlight, HIGH); // turn on headlights

      if( SRF6AServo.read() == servoMinPosition)
      {
        SRF6AServo.slowmove(servoMaxPosition,servoSpeeds) ;
      }
      else if( SRF6AServo.read() == servoMaxPosition)
      {
        SRF6AServo.slowmove(servoMinPosition,servoSpeeds) ;
      }     

      if(SRF6A.Ranging(CM) < 5){
        digitalWrite(buzzer, HIGH);      // we're going to crash
      }
      else {
        digitalWrite(buzzer, LOW);
      } 

      if (joystick[0] > 500 && joystick[0] < 540 && joystick[1] > 490 && joystick[1] < 530 )    // joystick is centered
      {
        stopped();
      }

      if (joystick[0] <= 500 && joystick[1] > 490 && joystick[1] < 530)               // joystick forward = all motors forward
      {
        fs = (map(joystick[0], 500, 0, 35, 255));
        forward(fs);
      }

      if (joystick[0] >= 540 && joystick[1] > 490 && joystick[1] < 530)               // joystick backward = all motors backward
      {
        bs = (map(joystick[0], 540, 1023, 35, 255));
        backward(bs);
      }

      if (joystick[1] <= 490 && joystick[0] > 500 && joystick[0] < 540)              // joystick left = left motors backward && right motors forward
      {
        ls = (map(joystick[1], 490, 0, 35, 255));
        turnleft(ls);
      }

      if (joystick[1] >= 530 && joystick[0] > 500 && joystick[0] < 540)              // joystick right = left motors forward && right motors backward
      {
        rs = (map(joystick[1], 530, 1023, 35, 255));
        turnright(rs);
      }
    }
    else {
      stopped();
      digitalWrite(headlight, LOW); // turn off headlights
    }
  }

  // 4 analog readings from motor controller = motor current
  for (int i=0; i<4; i++)
  {
    current[i] = analogRead( apin[i] )/ 1023.0 * 5.0;
  }

  unsigned long currentMillis = millis();

  if(currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;   

    radio.stopListening();
    bool ok = radio.write( &current, sizeof(current) );
    radio.startListening();
  }
}

void stopped()
{
  analogWrite(PWMM1, 0);
  analogWrite(PWMM2, 0);
  analogWrite(PWMM3, 0);
  analogWrite(PWMM4, 0);
  digitalWrite(orange, LOW);
}

void forward(int fs)
{
  digitalWrite(DirM1, HIGH);
  digitalWrite(DirM2, HIGH);
  digitalWrite(DirM3, HIGH);
  digitalWrite(DirM4, HIGH);
  analogWrite(PWMM1, fs);
  analogWrite(PWMM2, fs);
  analogWrite(PWMM3, fs);
  analogWrite(PWMM4, fs);
  digitalWrite(orange, LOW);
}

void backward(int bs)
{
  digitalWrite(DirM1, LOW);
  digitalWrite(DirM2, LOW);
  digitalWrite(DirM3, LOW);
  digitalWrite(DirM4, LOW);
  analogWrite(PWMM1, bs);
  analogWrite(PWMM2, bs);
  analogWrite(PWMM3, bs);
  analogWrite(PWMM4, bs);
  digitalWrite(orange, LOW);
}

void turnleft(int ls)
{
  digitalWrite(DirM1, LOW);
  digitalWrite(DirM2, LOW);
  digitalWrite(DirM3, HIGH);
  digitalWrite(DirM4, HIGH);
  analogWrite(PWMM1, ls);
  analogWrite(PWMM2, ls);
  analogWrite(PWMM3, ls);
  analogWrite(PWMM4, ls);
  digitalWrite(orange, HIGH);
}

void turnright(int rs)
{
  digitalWrite(DirM1, HIGH);
  digitalWrite(DirM2, HIGH);
  digitalWrite(DirM3, LOW);
  digitalWrite(DirM4, LOW);
  analogWrite(PWMM1, rs);
  analogWrite(PWMM2, rs);
  analogWrite(PWMM3, rs);
  analogWrite(PWMM4, rs);
  digitalWrite(orange, HIGH);
}

These sketches are becoming rather big, the transmitter sketch is more then 9000 bytes and the Rover 5 sketch is over 11000 bytes. The Dagu red back spider controller is based on the ATmega 1280 and has 128kb (minus the bootloader) of memory, I don’t think I will ever have to worry about running out of space
The transmitter or remote I currently use is an Arduino Duemilanove with a sensor shield on top of it. There is a nRF24L01 module, small joystick and I2C LCD display connected to it. You can find a picture of it here. The only thing that holds it all together are the wires connecting everything. So I’ve decided to make an enclosure for all these parts, I will have some plexiglass cut up to fit it all. I’ve ordered a joystick shield with some more buttons on it (always handy). And I’ve already received a 2×20 I2C LCD display, I will use a small 2 cell 500mAh Lipo battery to power it all. I bought 2 small 2 cell 500mAh Lipo batteries for 12,5€ on Ebay. I prefer them to AA batteries.