AUTHOR: Kevin Shin

Your show and tell can be about anything you accomplished other than research. This is about an action realized.

<aside> ❓ Tutorial: Clearly explain the necessary information and actions to arrive at an outcome

</aside>

Outcome

Initial Goal:

• As a part of the Proof Of Concept (POC) for moving Reachy's head which is based on 3-axis Orbita (3x DC motors + custom PCBs) we decided to use the Arduino + motor controller to drive the 3 DC motors.
• In addition, Raspberry Pi + camera module was required to send to command to Arduino to move the head (Orbita unit with 3x DC motors) followed by taking picture. We decided to use the I2C bus mainly for its scalability which allows the main Raspberry Pi to communication with multiple Arduinos (Head, Each Arms, and other sensors)

Realized Outcome:

• Prototype of the Reachy's Head unit represented by an Arduino + Dual channel L298 motor drivers + 2x DC motors wired up on a bread board (see graphic below for wiring)
• Modified example code found on the internet to ensure we are 1) able to drive both motors both clock wise & counter cloud wise, 2) both motors at the same time

Steps to achieve outcome

Outline/Framework/Recipe/Steps

1. Wire up a breadboard according to the wire diagram below. Pin assignment on the Arduino is important for the code to work properly. Test and connect DC power.

   

2. Example Code - Spins motors both direction & variable speed

// Each motor requires power (VCC, GND) & 3 pins
// Motor A connections - Arduino Pin Assignment
int enA = 9;
int in1 = 8;
int in2 = 7;
// Motor B connections - Arduino Pin Assignment
int enB = 3;
int in3 = 5;
int in4 = 4;

void setup() {
	// Set all the motor control pins to outputs
	pinMode(enA, OUTPUT);  // Controls speed for motor A
	pinMode(in1, OUTPUT);  // Direction for motor A
	pinMode(in2, OUTPUT);  // Direction for motor A

  pinMode(enB, OUTPUT);  // Controls speed for motor B
	pinMode(in3, OUTPUT);  // Direction for motor B
	pinMode(in4, OUTPUT);  // Direction for motor B
	
	// Turn off motors - Initial state
	digitalWrite(in1, LOW);
	digitalWrite(in2, LOW);
	digitalWrite(in3, LOW);
	digitalWrite(in4, LOW);
}

void loop() {
	directionControl();  // the motor will alternate between Clockwise & CounterClockwise
	delay(1000);
	speedControl();
	delay(1000);
}

// This function lets you control spinning direction of motors
void directionControl() {
	// Set motors to maximum speed
	// For PWM maximum possible values are 0 to 255
	analogWrite(enA, 255);
	analogWrite(enB, 255);

	// Turn on motor A & B
	digitalWrite(in1, HIGH);
	digitalWrite(in2, LOW);
	digitalWrite(in3, HIGH);
	digitalWrite(in4, LOW);
	delay(2000);
	
	// Now change motor directions
	digitalWrite(in1, LOW);
	digitalWrite(in2, HIGH);
	digitalWrite(in3, LOW);
	digitalWrite(in4, HIGH);
	delay(2000);
	
	// Turn off motors
	digitalWrite(in1, LOW);
	digitalWrite(in2, LOW);
	digitalWrite(in3, LOW);
	digitalWrite(in4, LOW);
}

// This function lets you control speed of the motors
void speedControl() {
	// Turn on motors
	digitalWrite(in1, LOW);
	digitalWrite(in2, HIGH);
	digitalWrite(in3, LOW);
	digitalWrite(in4, HIGH);
	
	// Accelerate from zero to maximum speed
	for (int i = 0; i < 256; i++) {
		analogWrite(enA, i);
		analogWrite(enB, i);
		delay(20);
	}
	
	// Decelerate from maximum speed to zero
	for (int i = 255; i >= 0; --i) {
		analogWrite(enA, i);
		analogWrite(enB, i);
		delay(20);
	}
	
	// Now turn off motors
	digitalWrite(in1, LOW);
	digitalWrite(in2, LOW);
	digitalWrite(in3, LOW);
	digitalWrite(in4, LOW);
}

To implement Arduino to listen on the I2C

1. Connect both Arduino (slave) and RaspberryPi (master) on the same I2C bus