STM32 LCD Library Which Is Written By Me It Doesn't Work

I have written an LDC driver for STM32f3xx. Wiring is correct but LCD doesn't work. LCD shows only white squares so I think data pins doesn't work correctly or there are logical error. I use char because data is 1 byte actually.

Here are the function's tasks:

• fallingEdge() : send to falling edge signal for the waking up LCD.

• send4BitMode() : LCD works in 4bit mode. So first of all, it will send MSB(4) bits to LCD. After, I use bitwise operator for shifting 4bit right so LSB(4) bits sent to LCD.

• sendCommand() : This function sends commands to LCD. (two times)

• sendCharacter() : This function sends characters to LCD. (two times)

Here is the lcd.h for prototype functions;

/*
 * lcd.h
 *  Created on: 1 Ara 2020
 *      Author: fatay
 */

/*
 * LCD Connection Pins for Using This Library
 * DataPin1  -> RB1
 * DataPin2  -> RB2
 * DataPin3  -> RB3
 * DataPin4  -> RB4
 * EPin      -> RB5
 * RSPin     -> RB6
 *
 */

#ifndef INC_LCD_H_
#define INC_LCD_H_

#include <stdint.h>
#include "stm32f3xx.h"

#define DataPin1 1
#define DataPin2 2
#define DataPin3 3
#define DataPin4 4
#define EPin     5
#define RSPin    6


void clearLCD(void);
void setCursorToFirstLine(void);
void setCursorToSecondLine(void);
void initLCD(void);
void writeLCD(char str);



#endif /* INC_LCD_H_ */

and this is the lcd.c file;

#include <stdlib.h>
#include "stm32f3xx_hal.h"
#include "lcd.h"

/*
 * LCD Connection Pins for Using This Library
 * DataPin1  -> RB1
 * DataPin2  -> RB2
 * DataPin3  -> RB3
 * DataPin4  -> RB4
 * EPin      -> RB5
 * RSPin     -> RB6
 *
 */


//for manipulating bits
#define SET_IF(expr)  ((expr) ? GPIO_PIN_SET : GPIO_PIN_RESET)
/*
 * We will be send falling edge signal
 * for waking up an LCD. So function
 * should be like this;
 *
 */

static void fallingEdge(void)
{
    HAL_GPIO_WritePin(GPIOB, EPin, GPIO_PIN_SET);
    HAL_Delay(1);
    HAL_GPIO_WritePin(GPIOB, EPin, GPIO_PIN_RESET);
}

/*
 * We send parallel 4 bit data in two times.
 * We will be getting first four (LSB) bits and then
 * the second one (MSB) bits.
 */

static void send4BitMode(char data)
{
    HAL_GPIO_WritePin(GPIOB, DataPin4, SET_IF(data & 0x08));
    HAL_GPIO_WritePin(GPIOB, DataPin3, SET_IF(data & 0x04));
    HAL_GPIO_WritePin(GPIOB, DataPin2, SET_IF(data & 0x02));
    HAL_GPIO_WritePin(GPIOB, DataPin1, SET_IF(data & 0x01));

    fallingEdge();
    HAL_Delay(1);

}

static void sendCommand(char command)
{
    HAL_GPIO_WritePin(GPIOB, RSPin, GPIO_PIN_RESET);
    send4BitMode(command >> 4);
    send4BitMode(command);
}

static void sendCharacter(char character)
{
    HAL_GPIO_WritePin(GPIOB, RSPin, GPIO_PIN_SET);
    send4BitMode(character >> 4);
    send4BitMode(character);
}


/*
 *
 * USER SCOPE
 *
 */



void clearLCD(void) {
    sendCommand(0x01);
}

void setCursorToFirstLine(void)
{
    sendCommand((char) 0x80);
}

void setCursorToSecondLine(void)
{
    sendCommand((char) 0x40);
}

void initLCD(void)
{
    HAL_GPIO_WritePin(GPIOB, EPin, GPIO_PIN_RESET);
    HAL_GPIO_WritePin(GPIOB, RSPin, GPIO_PIN_RESET);
    sendCommand((char) 0x20 | 0x00 | 0x08);
    HAL_Delay(5);

    clearLCD();
    setCursorToFirstLine();
    HAL_Delay(500);
}

void writeLCD(char str)
{
    sendCharacter(str);

}

thanks for your interest .