Problem with LCD panel not printing text

Hi!

I am making a stabilizer with a MPU6050 using a arduino uno. I am trying to print out the gyro values on a LCD screen but it just doesnt work. It lights up but nothing more, Ive tested printing out the gyro values and they exist and works. This is my code:

/*
Gyro - Arduino uno
VCC  -  5V
GND  -  GND
SDA  -  A4
SCL  -  A5

LCD  - Arduino Uno
VCC  -  5V
GND  -  GND
SDA  -  A4
SCL  -  A5
*/

//Include LCD and I2C library
#include <LiquidCrystal_I2C.h>
#include <Wire.h>

//Declaring some global variables
int gyro_x, gyro_y, gyro_z;
long acc_x, acc_y, acc_z, acc_total_vector;
int temperature;
long gyro_x_cal, gyro_y_cal, gyro_z_cal;
long loop_timer;
int lcd_loop_counter;
float angle_pitch, angle_roll;
int angle_pitch_buffer, angle_roll_buffer;
boolean set_gyro_angles;
float angle_roll_acc, angle_pitch_acc;
float angle_pitch_output, angle_roll_output;

//Initialize the LCD library
LiquidCrystal_I2C lcd(0x27,16,2);


void setup() {
  Wire.begin();                                                        //Start I2C as master
  Serial.begin(57600);                                                 //Use only for debugging
  pinMode(13, OUTPUT);                                                 //Set output 13 (LED) as output
  
  setup_mpu_6050_registers();                                          //Setup the registers of the MPU-6050 (500dfs / +/-8g) and start the gyro

  digitalWrite(13, HIGH);                                              //Set digital output 13 high to indicate startup

  lcd.begin();                                                         //Initialize the LCD
  lcd.backlight();                                                     //Activate backlight
  lcd.clear();                                                         //Clear the LCD

  lcd.setCursor(0,0);                                                  //Set the LCD cursor to position to position 0,0
  lcd.print("  MPU-6050 IMU");                                         //Print text to screen
  lcd.setCursor(0,1);                                                  //Set the LCD cursor to position to position 0,1
  lcd.print("     V1.0");                                              //Print text to screen

  delay(1500);                                                         //Delay 1.5 second to display the text
  lcd.clear();                                                         //Clear the LCD
  
  lcd.setCursor(0,0);                                                  //Set the LCD cursor to position to position 0,0
  lcd.print("Calibrating gyro");                                       //Print text to screen
  lcd.setCursor(0,1);                                                  //Set the LCD cursor to position to position 0,1
  for (int cal_int = 0; cal_int < 2000 ; cal_int ++){                  //Run this code 2000 times
    if(cal_int % 125 == 0)lcd.print(".");                              //Print a dot on the LCD every 125 readings
    read_mpu_6050_data();                                              //Read the raw acc and gyro data from the MPU-6050
    gyro_x_cal += gyro_x;                                              //Add the gyro x-axis offset to the gyro_x_cal variable
    gyro_y_cal += gyro_y;                                              //Add the gyro y-axis offset to the gyro_y_cal variable
    gyro_z_cal += gyro_z;                                              //Add the gyro z-axis offset to the gyro_z_cal variable
    delay(3);                                                          //Delay 3us to simulate the 250Hz program loop
  }
  gyro_x_cal /= 2000;                                                  //Divide the gyro_x_cal variable by 2000 to get the avarage offset
  gyro_y_cal /= 2000;                                                  //Divide the gyro_y_cal variable by 2000 to get the avarage offset
  gyro_z_cal /= 2000;                                                  //Divide the gyro_z_cal variable by 2000 to get the avarage offset

  lcd.clear();                                                         //Clear the LCD
  
  lcd.setCursor(0,0);                                                  //Set the LCD cursor to position to position 0,0
  lcd.print("Pitch:");                                                 //Print text to screen
  lcd.setCursor(0,1);                                                  //Set the LCD cursor to position to position 0,1
  lcd.print("Roll :");                                                 //Print text to screen
  
  digitalWrite(13, LOW);                                               //All done, turn the LED off
  
  loop_timer = micros();                                               //Reset the loop timer
}

void loop(){

  read_mpu_6050_data();                                                //Read the raw acc and gyro data from the MPU-6050

  gyro_x -= gyro_x_cal;                                                //Subtract the offset calibration value from the raw gyro_x value
  gyro_y -= gyro_y_cal;                                                //Subtract the offset calibration value from the raw gyro_y value
  gyro_z -= gyro_z_cal;                                                //Subtract the offset calibration value from the raw gyro_z value
  
  //Gyro angle calculations
  //0.0000611 = 1 / (250Hz / 65.5)
  angle_pitch += gyro_x * 0.0000611;                                   //Calculate the traveled pitch angle and add this to the angle_pitch variable
  angle_roll += gyro_y * 0.0000611;                                    //Calculate the traveled roll angle and add this to the angle_roll variable
  
  //0.000001066 = 0.0000611 * (3.142(PI) / 180degr) The Arduino sin function is in radians
  angle_pitch += angle_roll * sin(gyro_z * 0.000001066);               //If the IMU has yawed transfer the roll angle to the pitch angel
  angle_roll -= angle_pitch * sin(gyro_z * 0.000001066);               //If the IMU has yawed transfer the pitch angle to the roll angel
  
  //Accelerometer angle calculations
  acc_total_vector = sqrt((acc_x*acc_x)+(acc_y*acc_y)+(acc_z*acc_z));  //Calculate the total accelerometer vector
  //57.296 = 1 / (3.142 / 180) The Arduino asin function is in radians
  angle_pitch_acc = asin((float)acc_y/acc_total_vector)* 57.296;       //Calculate the pitch angle
  angle_roll_acc = asin((float)acc_x/acc_total_vector)* -57.296;       //Calculate the roll angle
  
  //Place the MPU-6050 spirit level and note the values in the following two lines for calibration
  angle_pitch_acc -= 0.0;                                              //Accelerometer calibration value for pitch
  angle_roll_acc -= 0.0;                                               //Accelerometer calibration value for roll

  if(set_gyro_angles){                                                 //If the IMU is already started
    angle_pitch = angle_pitch * 0.9996 + angle_pitch_acc * 0.0004;     //Correct the drift of the gyro pitch angle with the accelerometer pitch angle
    angle_roll = angle_roll * 0.9996 + angle_roll_acc * 0.0004;        //Correct the drift of the gyro roll angle with the accelerometer roll angle
  }
  else{                                                                //At first start
    angle_pitch = angle_pitch_acc;                                     //Set the gyro pitch angle equal to the accelerometer pitch angle 
    angle_roll = angle_roll_acc;                                       //Set the gyro roll angle equal to the accelerometer roll angle 
    set_gyro_angles = true;                                            //Set the IMU started flag
  }
  
  //To dampen the pitch and roll angles a complementary filter is used
  angle_pitch_output = angle_pitch_output * 0.9 + angle_pitch * 0.1;   //Take 90% of the output pitch value and add 10% of the raw pitch value
  angle_roll_output = angle_roll_output * 0.9 + angle_roll * 0.1;      //Take 90% of the output roll value and add 10% of the raw roll value
  
  write_LCD();                                                         //Write the roll and pitch values to the LCD display

  while(micros() - loop_timer < 4000);                                 //Wait until the loop_timer reaches 4000us (250Hz) before starting the next loop
  loop_timer = micros();                                               //Reset the loop timer
}


void read_mpu_6050_data(){                                             //Subroutine for reading the raw gyro and accelerometer data
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x3B);                                                    //Send the requested starting register
  Wire.endTransmission();                                              //End the transmission
  Wire.requestFrom(0x68,14);                                           //Request 14 bytes from the MPU-6050
  while(Wire.available() < 14);                                        //Wait until all the bytes are received
  acc_x = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_x variable
  acc_y = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_y variable
  acc_z = Wire.read()<<8|Wire.read();                                  //Add the low and high byte to the acc_z variable
  temperature = Wire.read()<<8|Wire.read();                            //Add the low and high byte to the temperature variable
  gyro_x = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_x variable
  gyro_y = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_y variable
  gyro_z = Wire.read()<<8|Wire.read();                                 //Add the low and high byte to the gyro_z variable

}

void write_LCD(){                                                      //Subroutine for writing the LCD
  //To get a 250Hz program loop (4us) it's only possible to write one character per loop
  //Writing multiple characters is taking to much time
  if(lcd_loop_counter == 14)lcd_loop_counter = 0;                      //Reset the counter after 14 characters
  lcd_loop_counter ++;                                                 //Increase the counter
  if(lcd_loop_counter == 1){
    angle_pitch_buffer = angle_pitch_output * 10;                      //Buffer the pitch angle because it will change
    lcd.setCursor(6,0);                                                //Set the LCD cursor to position to position 0,0
  }
  if(lcd_loop_counter == 2){
    if(angle_pitch_buffer < 0)lcd.print("-");                          //Print - if value is negative
    else lcd.print("+");                                               //Print + if value is negative
  }
  if(lcd_loop_counter == 3)lcd.print(abs(angle_pitch_buffer)/1000);    //Print first number
  if(lcd_loop_counter == 4)lcd.print((abs(angle_pitch_buffer)/100)%10);//Print second number
  if(lcd_loop_counter == 5)lcd.print((abs(angle_pitch_buffer)/10)%10); //Print third number
  if(lcd_loop_counter == 6)lcd.print(".");                             //Print decimal point
  if(lcd_loop_counter == 7)lcd.print(abs(angle_pitch_buffer)%10);      //Print decimal number

  if(lcd_loop_counter == 8){
    angle_roll_buffer = angle_roll_output * 10;
    lcd.setCursor(6,1);
  }
  if(lcd_loop_counter == 9){
    if(angle_roll_buffer < 0)lcd.print("-");                           //Print - if value is negative
    else lcd.print("+");                                               //Print + if value is negative
  }
  if(lcd_loop_counter == 10)lcd.print(abs(angle_roll_buffer)/1000);    //Print first number
  if(lcd_loop_counter == 11)lcd.print((abs(angle_roll_buffer)/100)%10);//Print second number
  if(lcd_loop_counter == 12)lcd.print((abs(angle_roll_buffer)/10)%10); //Print third number
  if(lcd_loop_counter == 13)lcd.print(".");                            //Print decimal point
  if(lcd_loop_counter == 14)lcd.print(abs(angle_roll_buffer)%10);      //Print decimal number
}

void setup_mpu_6050_registers(){
  //Activate the MPU-6050
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x6B);                                                    //Send the requested starting register
  Wire.write(0x00);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
  //Configure the accelerometer (+/-8g)
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x1C);                                                    //Send the requested starting register
  Wire.write(0x10);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
  //Configure the gyro (500dps full scale)
  Wire.beginTransmission(0x68);                                        //Start communicating with the MPU-6050
  Wire.write(0x1B);                                                    //Send the requested starting register
  Wire.write(0x08);                                                    //Set the requested starting register
  Wire.endTransmission();                                              //End the transmission
}

It is not my code so I do not tak credit for it, I am just trying to make it work :slight_smile:
Thanks beforehand!

Best regards Max

Did you ever get the LCD to work, by itself, running an example from the library that you are using?

There are several libraries with the name LiquidCrystal_I2C. The are not all the same and code from 1 may not run in another. Those LiquidCrystal_I2C libraries are old and most are not maintaned. The newest and absolute best library for I2C LCD with the hd44780 controller (1602, 2004) is the hd44780 library by Bill Perry.

Have you tried the contrast adjustment?

For an I2C LCD display to work, the I2C address and the I2C backpack to LCD pin mapping must be correct. If the library default settings for either or both are not correct the LCD will not work. You can try to figure out the right pin mapping and use an I2C scanner to find the address, but if you install and use the hd44780 library that is done automatically by the library.

To install the hd44780 library. The hd44780 library is the best available for I2C LCDs. The library is available in the Library Manager. Go to Library Manager (in the IDE menus, Sketch, Include Libraries, Manage Libraries) and in the Topics dropdown choose Display and in the Filter your search box enter hd44780. Select and install the hd44780 library by Bill Perry.

The class that you want to use is the hd44780_I2Cexp class. There are examples to show how to use the library. The nice thing about the hd44780 library is that it will autodetect the I2C address and the I2C backpack to LCD pin mapping.

In the examples, there is a diagnostic sketch that will help us to help you if you still have trouble with the display. Run the diagnostic sketch and post the results.

There are only a few changes needed for your code to run with the hd44780 library.

1 Like

0x3F
no 0x27

1 Like

@lordmax2, your topic has been moved to a more suitable location of the forum.

1 Like

If the display is showing nothing but the backlight, the first thing to check is the contrast adjustment.

If the contrast is set right it should, at least, show a row of blocks.

2 Likes

I tested 0x3F instead of 0x27, nothing happend. Yes @groundFungus only the backlight is on, how do you change the contrast?

I have the LCD connected to the same port as the MPU6050, could taht be the problem?

I am testing some examples but no one is working… the LCD panel I got is Geekcreit® iic / i2c 1602 blue backlight lcd display screen module geekcreit for arduino - products that work with official arduino boards Sale - Banggood.com

There should be a blue square thing on the I2C backpack. That is the contrast potentiometer. If you do not see it, post a photo of your LCD showing the backpack.

Is the backpack soldered to the LCD?

It should not be a problem. The 2 devices have different I2C addresses so should co-exist.

I changed the contrast, but the screen looks like this now

In your photo you have connected the LED pin somewhere? I only connected SDA and SCL

I changed back to 0x27 and its working!! What does that mean?

Good question next question is ok or?

1 Like

Turn the pot slowly back so that those blobs just disappear.

Great. That is a step in the right direction. Now go back and read reply #2 again. You need to get both the I2C address and the LCD to I2C backpack pin mapping right for it to work.

1 Like

It all works! Thanks for the help, I get the gyrovalues printed on the screen. Now its time to do some PID programming :slight_smile:

I have one lying around here (2004) where SDA and SCL are interchanged had almost trampled the, well a drunken Chinese

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