L293D SHIELD

// Simple Motor Shield sketch
// -----------------------------------
//
// By arduino.cc user "Krodal".
// June 2012
// Open Source / Public Domain
//
// Using Arduino 1.0.1
//
// A simple sketch for the motor shield,
// without using the Adafruit library.
//
// The outputs can be used for DC-motors 
// (either full H-bridge or just On and Off), lights, 
// relays, solenoids, etc.
// But stepper motors can not be used !
// Servo motors can be used with the default Servo library.
//
// A maximum of 4 DC motors can be used with full-bridge,
// or a maximum of 8 normal outputs, or a combination.
// Two servo motors can always be used, they use the +5V 
// of the Arduino board, so the voltage regulator could 
// get hot.
//
// Tested with an Ebay clone with the Arduino Uno.
//
// Parts of the code are from an old Adafruit Motor Shield
// library, which was public domain at that time.
// This code is also public domain
//
// This simplified program is using the normal 
// Arduino library functions as much as possible.
//
// The motors will make a whistling sound, 
// due to the analogWrite() PWM frequency.
// The Adafruit library is specifically designed to avoid
// this, so use the Adafruit library for a better result.
//
//
//
// Connector usage
// ---------------
// The order is different than what you would expect.
// If the Arduino (Uno) board is held with the USB
// connector to the left, the positive (A) side is 
// at the top (north), and the negative (B) side is 
// the bottom (south) for both headers.
//
//   Connector X1:
//     M1 on outside = MOTOR1_A   (+) north
//     M1 on inside  = MOTOR1_B   (-)
//     middle        = GND
//     M2 on inside  = MOTOR2_A   (+)
//     M2 on outside = MOTOR2_B   (-) south
//
//   Connector X2:
//     M3 on outside = MOTOR3_B   (-) south
//     M3 on inside  = MOTOR3_A   (+)
//     middle        = GND
//     M4 on inside  = MOTOR4_B   (-)
//     M4 on outside = MOTOR4_A   (+) north
//
//
//         -------------------------------
//         | -+s                         |
//         | -+s                         |
//    M1 A |                             | M4 A
//    M1 B |                             | M4 B
//    GND  |                             | GND
//    M2 A |                             | M3 A
//    M2 B |                             | M3 B
//         |                       ..... |
//         -------------------------------
//                + - 
//
//
//
// Pin usage with the Motorshield
// ---------------------------------------
// Analog pins: not used at all
//     A0 ... A5 are still available
//     They all can also be used as digital pins.
//     Also I2C (A4=SDA and A5=SCL) can be used.
//     These pins have a breadboard area on the shield.
// Digital pins: used: 3,4,5,6,7,8,9,10,11,12
//     Pin 9 and 10 are only used for the servo motors.
//     Already in use: 0 (RX) and 1 (TX).
//     Unused: 2,13
//     Pin 2 has an soldering hole on the board, 
//           easy to connect a wire.
//     Pin 13 is also connected to the system led.
// I2C is possible, but SPI is not possible since 
// those pins are used.
//


#include <Servo.h>


// Arduino pins for the shift register
#define MOTORLATCH 12
#define MOTORCLK 4
#define MOTORENABLE 7
#define MOTORDATA 8

// 8-bit bus after the 74HC595 shift register 
// (not Arduino pins)
// These are used to set the direction of the bridge driver.
#define MOTOR1_A 2
#define MOTOR1_B 3
#define MOTOR2_A 1
#define MOTOR2_B 4
#define MOTOR3_A 5
#define MOTOR3_B 7
#define MOTOR4_A 0
#define MOTOR4_B 6

// Arduino pins for the PWM signals.
#define MOTOR1_PWM 11
#define MOTOR2_PWM 3
#define MOTOR3_PWM 6
#define MOTOR4_PWM 5
#define SERVO1_PWM 10
#define SERVO2_PWM 9

// Codes for the motor function.
#define FORWARD 1
#define BACKWARD 2
#define BRAKE 3
#define RELEASE 4


// Declare classes for Servo connectors of the MotorShield.
Servo servo_1;
Servo servo_2;


void setup()
{
  Serial.begin(9600);
  Serial.println("Simple Motor Shield sketch");

  // Use the default "Servo" library of Arduino.
  // Attach the pin number to the servo library.
  // This might also set the servo in the middle position.
  servo_1.attach(SERVO1_PWM);
  servo_2.attach(SERVO2_PWM);
}


void loop()
{
  // Suppose there are two servo motors connected.
  // Let them move 180 degrees.
  servo_1.write(0);  
  delay(1000);
  servo_1.write(180);
  delay(2000);

  servo_2.write(0);
  delay(1000);
  servo_2.write(180);
  delay(2000);


  // Suppose there is a relay, or light or solenoid
  // connected to M3_A and GND.
  // Note that the 'speed' (the PWM, the intensity) 
  // is for both M3_A and M3_B.
  // The output is a push-pull output (half bridge), 
  // so it can also be used to drive something low.
  // The 'speed' (the PWM, the intensity) can be set 
  // to zero, that would make the output disabled 
  // and floating.
  motor_output(MOTOR3_A, HIGH, 255);
  delay(2000);
  motor_output(MOTOR3_A, LOW, 255);


  // Suppose a DC motor is connected to M1_A(+) and M1_B(-)
  // Let it run full speed forward and half speed backward.
  // If 'BRAKE' or 'RELEASE' is used, the 'speed' parameter
  // is ignored.
  motor(1, FORWARD, 255);
  delay(2000);
  // Be friendly to the motor: stop it before reverse.
  motor(1, RELEASE, 0);
  delay(500);
  motor(1, BACKWARD, 128);
  delay(2000);
  motor(1, RELEASE, 0);
}


// Initializing
// ------------
// There is no initialization function.
//
// The shiftWrite() has an automatic initializing.
// The PWM outputs are floating during startup, 
// that's okay for the Motor Shield, it stays off.
// Using analogWrite() without pinMode() is valid.
//


// ---------------------------------
// motor
//
// Select the motor (1-4), the command, 
// and the speed (0-255).
// The commands are: FORWARD, BACKWARD, BRAKE, RELEASE.
//
void motor(int nMotor, int command, int speed)
{
  int motorA, motorB;

  if (nMotor >= 1 && nMotor <= 4)
  {  
    switch (nMotor)
    {
    case 1:
      motorA   = MOTOR1_A;
      motorB   = MOTOR1_B;
      break;
    case 2:
      motorA   = MOTOR2_A;
      motorB   = MOTOR2_B;
      break;
    case 3:
      motorA   = MOTOR3_A;
      motorB   = MOTOR3_B;
      break;
    case 4:
      motorA   = MOTOR4_A;
      motorB   = MOTOR4_B;
      break;
    default:
      break;
    }

    switch (command)
    {
    case FORWARD:
      motor_output (motorA, HIGH, speed);
      motor_output (motorB, LOW, -1);     // -1: no PWM set
      break;
    case BACKWARD:
      motor_output (motorA, LOW, speed);
      motor_output (motorB, HIGH, -1);    // -1: no PWM set
      break;
    case BRAKE:
      // The AdaFruit library didn't implement a brake.
      // The L293D motor driver ic doesn't have a good
      // brake anyway.
      // It uses transistors inside, and not mosfets.
      // Some use a software break, by using a short
      // reverse voltage.
      // This brake will try to brake, by enabling 
      // the output and by pulling both outputs to ground.
      // But it isn't a good break.
      motor_output (motorA, LOW, 255); // 255: fully on.
      motor_output (motorB, LOW, -1);  // -1: no PWM set
      break;
    case RELEASE:
      motor_output (motorA, LOW, 0);  // 0: output floating.
      motor_output (motorB, LOW, -1); // -1: no PWM set
      break;
    default:
      break;
    }
  }
}


// ---------------------------------
// motor_output
//
// The function motor_ouput uses the motor driver to
// drive normal outputs like lights, relays, solenoids, 
// DC motors (but not in reverse).
//
// It is also used as an internal helper function 
// for the motor() function.
//
// The high_low variable should be set 'HIGH' 
// to drive lights, etc.
// It can be set 'LOW', to switch it off, 
// but also a 'speed' of 0 will switch it off.
//
// The 'speed' sets the PWM for 0...255, and is for 
// both pins of the motor output.
//   For example, if motor 3 side 'A' is used to for a
//   dimmed light at 50% (speed is 128), also the 
//   motor 3 side 'B' output will be dimmed for 50%.
// Set to 0 for completelty off (high impedance).
// Set to 255 for fully on.
// Special settings for the PWM speed:
//    Set to -1 for not setting the PWM at all.
//
void motor_output (int output, int high_low, int speed)
{
  int motorPWM;

  switch (output)
  {
  case MOTOR1_A:
  case MOTOR1_B:
    motorPWM = MOTOR1_PWM;
    break;
  case MOTOR2_A:
  case MOTOR2_B:
    motorPWM = MOTOR2_PWM;
    break;
  case MOTOR3_A:
  case MOTOR3_B:
    motorPWM = MOTOR3_PWM;
    break;
  case MOTOR4_A:
  case MOTOR4_B:
    motorPWM = MOTOR4_PWM;
    break;
  default:
    // Use speed as error flag, -3333 = invalid output.
    speed = -3333;
    break;
  }

  if (speed != -3333)
  {
    // Set the direction with the shift register 
    // on the MotorShield, even if the speed = -1.
    // In that case the direction will be set, but
    // not the PWM.
    shiftWrite(output, high_low);

    // set PWM only if it is valid
    if (speed >= 0 && speed <= 255)    
    {
      analogWrite(motorPWM, speed);
    }
  }
}


// ---------------------------------
// shiftWrite
//
// The parameters are just like digitalWrite().
//
// The output is the pin 0...7 (the pin behind 
// the shift register).
// The second parameter is HIGH or LOW.
//
// There is no initialization function.
// Initialization is automatically done at the first
// time it is used.
//
void shiftWrite(int output, int high_low)
{
  static int latch_copy;
  static int shift_register_initialized = false;

  // Do the initialization on the fly, 
  // at the first time it is used.
  if (!shift_register_initialized)
  {
    // Set pins for shift register to output
    pinMode(MOTORLATCH, OUTPUT);
    pinMode(MOTORENABLE, OUTPUT);
    pinMode(MOTORDATA, OUTPUT);
    pinMode(MOTORCLK, OUTPUT);

    // Set pins for shift register to default value (low);
    digitalWrite(MOTORDATA, LOW);
    digitalWrite(MOTORLATCH, LOW);
    digitalWrite(MOTORCLK, LOW);
    // Enable the shift register, set Enable pin Low.
    digitalWrite(MOTORENABLE, LOW);

    // start with all outputs (of the shift register) low
    latch_copy = 0;

    shift_register_initialized = true;
  }

  // The defines HIGH and LOW are 1 and 0.
  // So this is valid.
  bitWrite(latch_copy, output, high_low);

  // Use the default Arduino 'shiftOut()' function to
  // shift the bits with the MOTORCLK as clock pulse.
  // The 74HC595 shiftregister wants the MSB first.
  // After that, generate a latch pulse with MOTORLATCH.
  shiftOut(MOTORDATA, MOTORCLK, MSBFIRST, latch_copy);
  delayMicroseconds(5);    // For safety, not really needed.
  digitalWrite(MOTORLATCH, HIGH);
  delayMicroseconds(5);    // For safety, not really needed.
  digitalWrite(MOTORLATCH, LOW);
}