uses an ATTiny85 to drive a L293D driver

AttinyMotor.ino

//L293D
//Motor A
#define motorPin1 5  // Pin 14 of L293
#define motorPin2 2  // Pin 10 of L293
//Motor B
#define motorPin3 3 // Pin  7 of L293
#define motorPin4 4  // Pin  2 of L293

//ping sensor
#define echoPin 0
#define trigPin 1
long duration, distance;
long randint;

void ping(){
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance= duration*0.034/2;

}

void forward(){
	digitalWrite(motorPin1, HIGH);
    digitalWrite(motorPin2, LOW);
	digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin4, LOW);
}
void backward(){
	digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, HIGH);
	digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, HIGH);
}
void left(){
	digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, HIGH);
	digitalWrite(motorPin3, HIGH);
    digitalWrite(motorPin4, LOW);
}
void right(){
	digitalWrite(motorPin1, HIGH);
    digitalWrite(motorPin2, LOW);
	digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, HIGH);
}
void stop(){
	digitalWrite(motorPin1, LOW);
    digitalWrite(motorPin2, LOW);
	digitalWrite(motorPin3, LOW);
    digitalWrite(motorPin4, LOW);
}

void setup(){
    //Set pins as outputs
    pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
	pinMode(echoPin, INPUT); // Sets the echoPin as an Input
    pinMode(motorPin1, OUTPUT);
    pinMode(motorPin2, OUTPUT);
    pinMode(motorPin3, OUTPUT);
    pinMode(motorPin4, OUTPUT);
  	randomSeed(analogRead(0));
}

void loop(){
  ping();
  randint = random(11);
  if (distance<10){
    stop();
    delay(250);
    backward();
    delay(250);
    if (randint>=5){
      left();
      delay(500);
    } else {
      right();
      delay(500);
    }
  } else {
    forward();
  }
}