Transmitter.ino

 /* by HYPERARX (>‿◠)✌
 *  aravindvallab@protonmail.com
 *  Arduino Nano Transmitter for RC car
 */

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <Wire.h>

// Define the digital inputs

#define b3 2   // button 3
#define b4 3   // button 4
#define t1 4   // Toggle switch 1
#define t2 8   // Toggle switch 2
#define t3 5   // Toggle swich 3
#define t4 6   // Toggle switch 4
#define b1 1   // Button 1
#define b2 7   // Button 2
#define m  0   // button 5 (to initialize mpu6050)

const int MPU = 0x68; // MPU6050 I2C address
float AccX, AccY, AccZ;
float GyroX, GyroY, GyroZ;
float accAngleX, accAngleY, gyroAngleX, gyroAngleY;
float angleX, angleY;
float AccErrorX, AccErrorY, GyroErrorX, GyroErrorY;
float elapsedTime, currentTime, previousTime;

int c = 0;
RF24 radio(9, 10);   // nRF24L01 (CE, CSN)

const uint64_t pipeOut = 0xE9E8F0F0E1LL;   //IMPORTANT: The same as in the receiver 0xE9E8F0F0E1LL s
// Max size of this struct is 32 bytes - NRF24L01 buffer limit

struct Data_Package {
  byte j1PotX;
  byte j1PotY;
  byte button3;
  byte j2PotX;
  byte j2PotY;
  byte button4;
  byte pot1;
  byte pot2;
  byte tSwitch1;
  byte tSwitch2;
  byte tSwitch3;
  byte tSwitch4;
  byte button1;
  byte button2;
};
Data_Package data; //Create a variable with the above structure

void setup() {
  Serial.begin(9600);
  
  // Initialize interface to the MPU6050
  initialize_MPU6050();
  // Call this function if you need to get the IMU error values for your module
  //calculate_IMU_error();
  
  // Define the radio communication
  radio.begin();
  radio.openWritingPipe(pipeOut);
  radio.setAutoAck(false);
  radio.setDataRate(RF24_250KBPS);
  radio.setPALevel(RF24_PA_LOW);
  
  // Activate the Arduino internal pull-up resistors
  pinMode(b3, INPUT_PULLUP);
  pinMode(b4, INPUT_PULLUP);
  pinMode(t1, INPUT_PULLUP);
  pinMode(t2, INPUT_PULLUP);
  pinMode(t3, INPUT_PULLUP);
  pinMode(t4, INPUT_PULLUP);
  pinMode(b1, INPUT_PULLUP);
  pinMode(b2, INPUT_PULLUP);
  pinMode(m,  INPUT_PULLUP);
  
  // Set initial default values
  data.j1PotX = 127.5; // Values from 0 to 255. When Joystick is in resting position, the value is in the middle, or 127. We actually map the pot value from 0 to 1023 to 0 to 255 because that's one BYTE value
  data.j1PotY = 127.5;
  data.j2PotX = 127.5;
  data.j2PotY = 127.5;
  data.button3 = 1;
  data.button4 = 1;
  data.pot1 = 1;
  data.pot2 = 1;
  data.tSwitch1 = 1;
  data.tSwitch2 = 1;
  data.tSwitch3 = 1;
  data.tSwitch4 = 1;
  data.button1 = 1;
  data.button2 = 1;
}
void loop() {
  
  // Read all analog inputs and map them to one Byte value  joysticks and rotary potentiometer
  data.j1PotX = map(analogRead(A1), 0, 1023, 0, 255); // Convert the analog read value from 0 to 1023 into a BYTE value from 0 to 255
  data.j1PotY = map(analogRead(A0), 0, 1023, 0, 255);
  data.j2PotX = map(analogRead(A2), 0, 1023, 0, 255);
  data.j2PotY = map(analogRead(A3), 0, 1023, 0, 255);
  data.pot1 = map(analogRead(A7), 0, 1023, 0, 255);
  data.pot2 = map(analogRead(A6), 0, 1023, 0, 255);
  
  // Read all digital inputs     tactile & toggle switch 
  data.button3 = digitalRead(b3);
  data.button4 = digitalRead(b4);
  data.tSwitch2 = digitalRead(t2);
  data.tSwitch1 = digitalRead(t1);
  data.tSwitch3 = digitalRead(t3);
  data.tSwitch4 = digitalRead(t4);
  data.button1 = digitalRead(b1);
  data.button2 = digitalRead(b2);
  
  // If toggle switch m is switched on
  if (digitalRead(m) == 0) {
    read_IMU();    // Use MPU6050 instead of Joystick 1 for controling left, right, forward and backward movements
  }
  // Send the whole data from the structure to the receiver
  radio.write(&data, sizeof(Data_Package));
}

void initialize_MPU6050() {
  
  Wire.begin();                      // Initialize comunication
  Wire.beginTransmission(MPU);       // Start communication with MPU6050 // MPU=0x68
  Wire.write(0x6B);                  // Talk to the register 6B
  Wire.write(0x00);                  // Make reset - place a 0 into the 6B register
  Wire.endTransmission(true);        //end the transmission
  // Configure Accelerometer
  Wire.beginTransmission(MPU);
  Wire.write(0x1C);                  //Talk to the ACCEL_CONFIG register
  Wire.write(0x10);                  //Set the register bits as 00010000 (+/- 8g full scale range)
  Wire.endTransmission(true);
  // Configure Gyro
  Wire.beginTransmission(MPU);
  Wire.write(0x1B);                   // Talk to the GYRO_CONFIG register (1B hex)
  Wire.write(0x10);                   // Set the register bits as 00010000 (1000dps full scale)
  Wire.endTransmission(true);
}
void calculate_IMU_error() {
  // We can call this funtion in the setup section to calculate the accelerometer and gury data error. From here we will get the error values used in the above equations printed on the Serial Monitor.
  // Note that we should place the IMU flat in order to get the proper values, so that we then can the correct values
  // Read accelerometer values 200 times
  while (c < 200) {
    Wire.beginTransmission(MPU);
    Wire.write(0x3B);
    Wire.endTransmission(false);
    Wire.requestFrom(MPU, 6, true);
    AccX = (Wire.read() << 8 | Wire.read()) / 4096.0 ;
    AccY = (Wire.read() << 8 | Wire.read()) / 4096.0 ;
    AccZ = (Wire.read() << 8 | Wire.read()) / 4096.0 ;
    // Sum all readings
    AccErrorX = AccErrorX + ((atan((AccY) / sqrt(pow((AccX), 2) + pow((AccZ), 2))) * 180 / PI));
    AccErrorY = AccErrorY + ((atan(-1 * (AccX) / sqrt(pow((AccY), 2) + pow((AccZ), 2))) * 180 / PI));
    c++;
  }
  //Divide the sum by 200 to get the error value
  AccErrorX = AccErrorX / 200;
  AccErrorY = AccErrorY / 200;
  c = 0;
  // Read gyro values 200 times
  while (c < 200) {
    Wire.beginTransmission(MPU);
    Wire.write(0x43);
    Wire.endTransmission(false);
    Wire.requestFrom(MPU, 4, true);
    GyroX = Wire.read() << 8 | Wire.read();
    GyroY = Wire.read() << 8 | Wire.read();
    // Sum all readings
    GyroErrorX = GyroErrorX + (GyroX / 32.8);
    GyroErrorY = GyroErrorY + (GyroY / 32.8);
    c++;
  }
  //Divide the sum by 200 to get the error value
  GyroErrorX = GyroErrorX / 200;
  GyroErrorY = GyroErrorY / 200;
  // Print the error values on the Serial Monitor
  Serial.print("AccErrorX: ");
  Serial.println(AccErrorX);
  Serial.print("AccErrorY: ");
  Serial.println(AccErrorY);
  Serial.print("GyroErrorX: ");
  Serial.println(GyroErrorX);
  Serial.print("GyroErrorY: ");
  Serial.println(GyroErrorY);
}
void read_IMU() {
  // === Read acceleromter data === //
  Wire.beginTransmission(MPU);
  Wire.write(0x3B); // Start with register 0x3B (ACCEL_XOUT_H)
  Wire.endTransmission(false);
  Wire.requestFrom(MPU, 6, true); // Read 6 registers total, each axis value is stored in 2 registers
  //For a range of +-8g, we need to divide the raw values by 4096, according to the datasheet
  AccX = (Wire.read() << 8 | Wire.read()) / 4096.0; // X-axis value
  AccY = (Wire.read() << 8 | Wire.read()) / 4096.0; // Y-axis value
  AccZ = (Wire.read() << 8 | Wire.read()) / 4096.0; // Z-axis value
  // Calculating angle values using
  accAngleX = (atan(AccY / sqrt(pow(AccX, 2) + pow(AccZ, 2))) * 180 / PI) + 1.15; // AccErrorX ~(-1.15) See the calculate_IMU_error()custom function for more details
  accAngleY = (atan(-1 * AccX / sqrt(pow(AccY, 2) + pow(AccZ, 2))) * 180 / PI) - 0.52; // AccErrorX ~(0.5)
  // === Read gyro data === //
  previousTime = currentTime;        // Previous time is stored before the actual time read
  currentTime = millis();            // Current time actual time read
  elapsedTime = (currentTime - previousTime) / 1000;   // Divide by 1000 to get seconds
  Wire.beginTransmission(MPU);
  Wire.write(0x43); // Gyro data first register address 0x43
  Wire.endTransmission(false);
  Wire.requestFrom(MPU, 4, true); // Read 4 registers total, each axis value is stored in 2 registers
  GyroX = (Wire.read() << 8 | Wire.read()) / 32.8; // For a 1000dps range we have to divide first the raw value by 32.8, according to the datasheet
  GyroY = (Wire.read() << 8 | Wire.read()) / 32.8;
  GyroX = GyroX + 1.85; //// GyroErrorX ~(-1.85)
  GyroY = GyroY - 0.15; // GyroErrorY ~(0.15)
  // Currently the raw values are in degrees per seconds, deg/s, so we need to multiply by sendonds (s) to get the angle in degrees
  gyroAngleX = GyroX * elapsedTime;
  gyroAngleY = GyroY * elapsedTime;
  // Complementary filter - combine acceleromter and gyro angle values
  angleX = 0.98 * (angleX + gyroAngleX) + 0.02 * accAngleX;
  angleY = 0.98 * (angleY + gyroAngleY) + 0.02 * accAngleY;
  // Map the angle values from -90deg to +90 deg into values from 0 to 255, like the values we are getting from the Joystick
  data.j1PotX = map(angleX, -90, +90, 255, 0);
  data.j1PotY = map(angleY, -90, +90, 0, 255);
}