STM32F103C8T6 can not communicate with HD44780 - stm32

Question

I'm trying to control a HD44780 16X2 LCD(4 bit
communication) using a STM32F103C8T6.
I connected the LCD this way:
RS => PA0
EN => PA2
RW Ground
D7 => PB7
D6 => PB6
D5 => PB5
D4 => PB4
The LCD doesn't display anything. Where might the problem be? Does anyone know something about this issue?
Here is my code:
#include "delay.h"
#include "stm32f10x.h" // Device header
void lcd_command(unsigned char command);
void lcd_init(void);
void lcdPosition(unsigned int row, unsigned int column);
void lcd_data(unsigned char data);
int main() {
delay_init();
RCC->APB2ENR |= 1 << 2; // Port A Enabled.
RCC->APB2ENR |= 1 << 3; // Port B Enabled.
GPIOA->CRL = 0x22222222; // A0 and A2 Output.
GPIOB->CRL = 0x22222222; // B7,B6,B5,B4 Output.
GPIOB->ODR = 0x00; // Port B clear.
delay_ms(20);
lcd_command(0x30); // Datasheet says.
delay_ms(5);
lcd_command(0x30); // Datasheet says.
delay_ms(1);
lcd_command(0x30); // Datasheet says.
delay_ms(1);
lcd_init();
lcdPosition(1, 1); // first row first column
delay_ms(1);
lcd_data('A'); // Letter A
while (1)
;
}
void lcd_command(unsigned char command) {
GPIOA->BRR |= 1 << 0; // RS reset.
GPIOA->BSRR |= 1 << 2; // E set.
GPIOB->ODR = command; // upper nibble
delay_ms(2); // delay
GPIOA->BRR |= 1 << 2; // E reset.
GPIOB->BRR = 0x000000F0; // clear data bits
delay_ms(2); // delay
command = command << 4; // lower nibble
GPIOA->BSRR |= 1 << 2; // E set.
GPIOB->ODR = command; // lower nibble
delay_ms(2); // delay
GPIOA->BRR |= 1 << 2; // E reset.
GPIOB->BRR = 0x000000FF; // clear data bits
}
void lcd_init() {
lcd_command(0x02); // Return
delay_ms(2); // delay
lcd_command(0x28);
set 4 - bit data, 2 - line, 5x7 font delay_ms(2); // delay
lcd_command(0x0C);
turn on display, cursor off.delay_ms(2); // delay
lcd_command(0x01); // Clear.
delay_ms(2); // delay
lcd_command(0x06);
move cursor right delay_ms(4); // delay
}
void lcdPosition(unsigned int row, unsigned int column) {
if (row == 1) {
column--;
lcd_command(0x80 + column); // Define row
} else if (row == 2) {
column--;
lcd_command(0xC0 + column); // Define column
}
}
void lcd_data(unsigned char data) {
GPIOA->BSRR |= 1 << 0; // RS reset.
GPIOA->BSRR |= 1 << 2; // E set.
GPIOB->ODR = data;
upper nibble first delay_ms(4); // delay
GPIOA->BRR |= 1 << 2; // E reset.
GPIOB->BRR = 0x000000F0; // clear data bits
delay_ms(4); // delay
data = data << 4; // lower nibble
GPIOA->BSRR |= 1 << 2; // E set.
GPIOB->ODR = data; // lower nibble
delay_ms(4); // delay
GPIOA->BRR |= 1 << 2; // E reset.
GPIOB->BRR = 0x000000FF; // clear data bits
}

Answer 1

Also PA0 and PA2 are not 5V tolerant pins, usually HD44780 is 5V device, if it runs on +5V refer to the datasheet in Table 5. "Medium-density STM32F103xx pin definitions", if the pin is 5V tolerant in column I/O level it should be denoted with FT!

Answer 2

Please read carefully how to initialize 4-bit interface in the datasheet at page 46, figure 24.
In short: your lcd_command sends two nibbles one after another, but you are required to send only one nibble for first several commands (since the display controller still is in the 8-bit mode). You'll need to have a separate function to send only one nibble.