Raspberry Pi Auto Etch A Sketch™︎ -- Episode 372

Raspberry Pi Auto Etch A Sketch

element14 presents  |  daftmike's VCP Profile  |  Project Videos

You don't have permission to edit metadata of this video. Edit media Dimensions x Small Medium Large Custom Subject (required) Brief Description Tags (separated by comma) Video visibility in search results Visible Hidden Parent content Raspberry Pi Auto Etch A Sketch™︎ -- Episode 372 Poster Upload Preview Ok Cancel

In this video Mike builds an automatic Etch A Sketch machine using stepper motors and 3D printed gears.

Bill of Material:

Arduino Flip Code:

/* ================================================================================


  GY-521 IMU test code for flipping the etch a sketch - daftmike 2018


  ================================================================================ */





#include <Wire.h>


#include <Servo.h>





// Servo is attached to pin 5


Servo servo;


const int servoPin = 5;





// Variables used for the IMU readings


long accelX, accelY, accelZ;


float gForceX, gForceY, gForceZ;


long gyroXCali = 0, gyroYCali = 0, gyroZCali = 0;


long gyroXPresent = 0, gyroYPresent = 0, gyroZPresent = 0;


long gyroXPast = 0, gyroYPast = 0, gyroZPast = 0;


float rotX, rotY, rotZ;


float angleX = 0, angleY = 0, angleZ = 0;


long timePast = 0;


long timePresent = 0;





// Variables used to keep track of the 'flip'


bool flipStarted = 0;


bool flipFinished = 0;


int flips = 0;


int servoDir = 90;





// String to hold the serial data from the Pi


String piMsg;





// Speed, angle and number of 'flips'


const int forwardSpeed = 60;


const int backwardSpeed = 180;


const int numFlips = 5;


const int lowAngle = -140;


const int midAngle = -120;








/*================================================================================*/





void setup() {


  Serial.begin(9600);  // start the serial port


  Wire.begin();  // start i2c


  setUpMPU();  // start IMU coms


  calibrateGyroValues();  


  timePresent = millis();  // time reference for IMU readings


}





/*================================================================================*/





void loop() {


  readAndProcessAccelData();


  readAndProcessGyroData();


  readPi();


}





/*================================================================================*/





void servoFlip() {  


  if (servoDir == 90) {


  servo.attach(servoPin);


  servoDir = forwardSpeed;


  servo.write(servoDir);


  Serial.println("flip started, servo moving forward...");


  flipStarted = 1;


  }





  if (flipStarted == 1) {





   if (servoDir == forwardSpeed && angleX < lowAngle && flips < numFlips) {


  servoDir = backwardSpeed;


  servo.write(servoDir);


  Serial.println("servo backward...");


  flips++;


  Serial.print("flip number: ");


  Serial.println(flips);


  }


   if (servoDir == backwardSpeed && angleX > midAngle && flips < numFlips) {


  servoDir = forwardSpeed;


  servo.write(servoDir);


  Serial.println("servo forward...");


  flips++;


  Serial.print("flip number: ");


  Serial.println(flips);


  }


   if (servoDir == backwardSpeed && -2 < angleX) {


  Serial.println("turning servo OFF...");


  servo.detach();


  servoDir = 90;


  flips = 0;


  flipStarted = 0;


   delay(2000);


   setUpMPU();


   calibrateGyroValues();


  }


  }


}





void readPi() {  // read data from the serial port into a string to check for messages





  if (Serial.available()) {


  piMsg = Serial.readString();





   if (piMsg == "flip") {


   servoFlip();


  }


   else if (piMsg == "cali") {


  Serial.println("calibrating gyro values...");


   setUpMPU();


   calibrateGyroValues();


  }


  }


}








void setUpMPU() {


  // power management


  Wire.beginTransmission(0b1101000);  // Start the communication by using address of MPU


  Wire.write(0x6B);  // Access the power management register


  Wire.write(0b00000000);  // Set sleep = 0


  Wire.endTransmission();  // End the communication





  // configure gyro


  Wire.beginTransmission(0b1101000);


  Wire.write(0x1B);  // Access the gyro configuration register


  Wire.write(0b00000000);


  Wire.endTransmission();





  // configure accelerometer


  Wire.beginTransmission(0b1101000);


  Wire.write(0x1C);  // Access the accelerometer configuration register


  Wire.write(0b00000000);


  Wire.endTransmission();


}





void calibrateGyroValues() {


  for (int i = 0; i < 5000; i++) {


   getGyroValues();


  gyroXCali = gyroXCali + gyroXPresent;


  gyroYCali = gyroYCali + gyroYPresent;


  gyroZCali = gyroZCali + gyroZPresent;


  }


  gyroXCali = gyroXCali / 5000;


  gyroYCali = gyroYCali / 5000;


  gyroZCali = gyroZCali / 5000;


}





void readAndProcessAccelData() {


  Wire.beginTransmission(0b1101000);


  Wire.write(0x3B);


  Wire.endTransmission();


  Wire.requestFrom(0b1101000, 6);


  while (Wire.available() < 6);


  accelX = Wire.read() << 8 | Wire.read();


  accelY = Wire.read() << 8 | Wire.read();


  accelZ = Wire.read() << 8 | Wire.read();


  processAccelData();


}





void processAccelData() {


  gForceX = accelX / 16384.0;


  gForceY = accelY / 16384.0;


  gForceZ = accelZ / 16384.0;


}





void readAndProcessGyroData() {


  gyroXPast = gyroXPresent;  // Assign Present gyro reaging to past gyro reading


  gyroYPast = gyroYPresent;  // Assign Present gyro reaging to past gyro reading


  gyroZPast = gyroZPresent;  // Assign Present gyro reaging to past gyro reading


  timePast = timePresent;  // Assign Present time to past time


  timePresent = millis();  // get the current time in milli seconds, it is the present time





  getGyroValues();  // get gyro readings


  getAngularVelocity();  // get angular velocity


  calculateAngle();  // calculate the angle


}





void getGyroValues() {


  Wire.beginTransmission(0b1101000);  // Start the communication by using address of MPU


  Wire.write(0x43);  // Access the starting register of gyro readings


  Wire.endTransmission();


  Wire.requestFrom(0b1101000, 6);  // Request for 6 bytes from gyro registers (43 - 48)


  while (Wire.available() < 6);  // Wait untill all 6 bytes are available


  gyroXPresent = Wire.read() << 8 | Wire.read();  // Store first two bytes into gyroXPresent


  gyroYPresent = Wire.read() << 8 | Wire.read();  // Store next two bytes into gyroYPresent


  gyroZPresent = Wire.read() << 8 | Wire.read();  // Store last two bytes into gyroZPresent


}





void getAngularVelocity() {


  rotX = gyroXPresent / 131.0;


  rotY = gyroYPresent / 131.0;


  rotZ = gyroZPresent / 131.0;


}





void calculateAngle() {


  // same equation can be written as


  // angleZ = angleZ + ((timePresentZ - timePastZ)*(gyroZPresent + gyroZPast - 2*gyroZCalli)) / (2*1000*131);


  // 1/(1000*2*131) = 0.00000382


  // 1000 --> convert milli seconds into seconds


  // 2 --> comes when calculation area of trapezium


  // substacted the callibated result two times because there are two gyro readings


  angleX = angleX + ((timePresent - timePast) * (gyroXPresent + gyroXPast - 2 * gyroXCali)) * 0.00000382;


  angleY = angleY + ((timePresent - timePast) * (gyroYPresent + gyroYPast - 2 * gyroYCali)) * 0.00000382;


  angleZ = angleZ + ((timePresent - timePast) * (gyroZPresent + gyroZPast - 2 * gyroZCali)) * 0.00000382;


}





void printData() {


  Serial.print("X : ");


  Serial.print(angleX);


  Serial.print("° | Y : ");


  Serial.print(angleY);


  Serial.print("° | Z : ");


  Serial.print(angleZ); Serial.println("°");





}

Supporting Files:

Click Here for access to all the supporting files you will need to replicate this build!