[SOLVED] my LCD HD44780 connected to STM32F103rb shows nothing

[lucas_mur]

Hey, It's been a while that I'm trying to display character in my LCD HD44780 which is connected to Nucleo STM32F103RB board, but without any success. That's why I'm here to find any suggestion or solution about that. For the connection, I connect the LCD with the board via :
VSS = GND
VDD = 5V
VO = with the resistance 10Kohm
RS = PB0
RW = GND
E = PB1
D4 = PB2
D5 = PB3
D6 = PB4
D7 = PB5
Everthing is Ok with pins, the LCD turn On. when I change the resistance, I see the black rectangles in the first line. Here the code that I'm using for the LCD according to the datasheet found in the LCD vendor webiste, the code explanation is bellow the code.

#include "stm32f103xb.h"
#include <unistd.h>
#define LCD_RS_ON() GPIOB->ODR |= 1<<0;
#define LCD_RS_OFF() GPIOB->ODR &= ~(1<<0);
#define LCD_E_ON() GPIOB->ODR |= 1<<1;
#define LCD_E_OFF() GPIOB->ODR &= ~(1<<1);
#define LCD_PB2_ON() GPIOB->ODR |= 1<<2;
#define LCD_PB2_OFF() GPIOB->ODR &= ~(1<<2);
#define LCD_PB3_ON() GPIOB->ODR |= 1<<3;
#define LCD_PB3_OFF() GPIOB->ODR &= ~(1<<3);
#define LCD_PB4_ON() GPIOB->ODR |= 1<<4;
#define LCD_PB4_OFF() GPIOB->ODR &= ~(1<<4);
#define LCD_PB5_ON() GPIOB->ODR |= 1<<5;
#define LCD_PB5_OFF() GPIOB->ODR &= ~(1<<5);


void SystemClockConfig(void);
void init_Timer(void);
void init_GPIO(void);
void _lcdWrite8bits(uint8_t data, uint8_t rs);
void lcdInit();
void lcdPutc(char c, uint8_t line);
static void delay_us(int us);
void lcd_toggle_enable (void);



int main(void){
    SystemClockConfig();
    init_Timer();
    init_GPIO();
    lcdInit();
    lcdPutc('A',0);
    while(1);
    return 0;
}
void _lcdWrite8bits(uint8_t data, uint8_t rs){
    if(rs){
        LCD_RS_ON();
    }
    else{
        LCD_RS_OFF();
    }
    LCD_PB2_OFF();
    LCD_PB3_OFF();
    LCD_PB4_OFF();
    LCD_PB5_OFF();
    if((data & 0x10) == 0x10){
        LCD_PB2_ON();
    }
    if((data & 0x20) == 0x20){
        LCD_PB3_ON();
    }
    if((data & 0x40) == 0x40){
        LCD_PB4_ON();
    }
    if((data & 0x80) == 0x80){
        LCD_PB5_ON();
    }
    lcd_toggle_enable();
    LCD_PB2_OFF();
    LCD_PB3_OFF();
    LCD_PB4_OFF();
    LCD_PB5_OFF();
    if((data & 0x01) == 0x01){
        LCD_PB2_ON();
    }
    if((data & 0x02) == 0x02){
        LCD_PB3_ON();
    }
    if((data & 0x04) == 0x04){
        LCD_PB4_ON();
    }
    if((data & 0x08) == 0x08){
        LCD_PB5_ON();
    }
    lcd_toggle_enable();
}
void lcd_toggle_enable (void){
    delay_us(500);
    LCD_E_ON();
    delay_us(500);
    LCD_E_OFF();
    delay_us(500);
}
void lcdInit(){
    delay_us(20000);
    _lcdWrite8bits(0x33,0);
    _lcdWrite8bits(0x32,0);
    _lcdWrite8bits(0x06,0);
    _lcdWrite8bits(0x0C,0);
    _lcdWrite8bits(0x28,0);
    _lcdWrite8bits(0x01,0);
    delay_us(500);
}
void lcdPutc(char c, uint8_t line){
    uint8_t LIGNE_1 = 0x80;
    uint8_t LIGNE_2 = 0xC0;
    if(line ==0){
        _lcdWrite8bits(LIGNE_1, 0);
    }
    else if (line==1){
        _lcdWrite8bits(LIGNE_2, 0);
    }
    _lcdWrite8bits(c, 1);
}
void SystemClockConfig(){
    //activation HSI -> HSION
    RCC->CR &= 0;
    RCC->CR |= 1;
    /*Attender la mise en place de HSI HSIRDY*/
    while (!(RCC->CR & (1<<1))){}
  
    // PLL prendre un facteur 9
    RCC->CFGR |= (0b0111 << 18);
    //Activer le PLL -> PLLON
    RCC->CR |= (1 << 24);
    /*Attendre l'activation de PLL-> PLLRDY*/
    while (!(RCC->CR & (1<<25))){}
    /*Metre PLL comme clock source*/
    RCC->CFGR &= ~0b11;
    RCC->CFGR |= 0b10;
    /*Attendre le changement de clock source */
    while (!(RCC->CFGR & (0b10<<2))){}
    /*Prescaler 2 pour APB1*/
    RCC->CFGR &= ~(0b111 << 8);
    RCC->CFGR |= 0b100 << 8;
}
void init_GPIO(void){
    RCC->APB2ENR &=~(1 << 3); // clear RCC for GPIOB
    RCC->APB2ENR |= (1 << 3); // Enable RCC for GPIOB
    GPIOB->CRL &= ~((1 << 3) | (1 << 2) | (1 << 1) | (1 << 0)); // Clear GPIO PB0 MODE
    GPIOB->CRL &= ~((1 << 6) | (1 << 5) | (1 << 7) | (1 << 4)); // Clear GPIO PB1 MODE
    GPIOB->CRL &= ~((1 << 11) | (1 << 10) | (1 << 9) | (1 << 8)); // Clear GPIO PB2 MODE
    GPIOB->CRL &= ~((1 << 15) | (1 << 14) | (1 << 13) | (1 << 12)); // Clear GPIO PB3 MODE
    GPIOB->CRL &= ~((1 << 16) | (1 << 17) | (1 << 18) | (1 << 19)); // Clear GPIO PB4 MODE
    GPIOB->CRL &= ~((1 << 20) | (1 << 21) | (1 << 22) | (1 << 23)); // Clear GPIO PB5 MODE
    GPIOB->CRL |= 0x00222222; // Set GPIO PB0--->5 MODE (01 : output)
}
void init_Timer(void){
        RCC->APB1ENR &= 0 << 0;
        RCC->APB1ENR |= 1 << 0;
        TIM2->PSC = 35;
        TIM2->ARR = 30000;
        TIM2->EGR |= 1;
        TIM2->CR1 |= 1;
}
static void delay_us(int us)
{
        TIM2->CNT = 0;
    while(TIM2->CNT <= us );   
}

For my code, I started by configuring the board clock which I use 36Mhz, then I initialize the the port (Port B) and the pins used in LCD (PB0 to PB5). I also use Timer 2 in order to create a delay function, the delay is in microsecond unit. Finally I follow the the datasheet to initialize the LCD and display the characters. So if anyone could highlight me about the issue or suggested solution.

 

[KlausST]

Hi,

Please post a schematic.

I see "5V" ... are the nucleo signals also 5V?

"With the resistance 10k" is meaningless.

Klaus

 

[betwixt]

I can't confirm this but you seem to write bytes to the LCD without any delay between them. For example in "lcdInit()" you correctly allow time for the HD44780 to initialize and correctly add a short delay afterwards but the individual bytes are sent immediately one after the other. At 32MHz clock speed this is probably too fast for the LCD to 'digest' them.

Brian.

 

[lucas_mur]

How it looks like my circuit, when I power ON

 

[lucas_mur]

Hi,

Please post a schematic.

I see "5V" ... are the nucleo signals also 5V?

"With the resistance 10k" is meaningless.

Klaus

Here is my circuit when I power On the board. Concerning '5V', I think you're right, I learned somewhere that the board pins works with 3.3V but the LCD works with 5V. but in LCD characteristics they mention that LCD voltage range is 3.3V - 5V

 

[KlausST]

Hi,

We don´t know your level of electronics knowledge.
It´s not only that a device (display in your case) need "any" supply voltage within it´s specified range, it also needs the correct timing and the correct signal levels.

We professionals get our informations from reading the datasheets. I think it´s not the worst way .. to design reliable circuits.

Btw: especially for those displays there are many tutorials around, even videos, example schematis, expample code, a lot of forum discussions.

Maybe just have a look at the box below "similar questions".

Klaus

 

[Aussie Susan]

When you get the blocks like that on the display, it generally means that the contrast is too high. You need to put a potentiometer in the contrast supply line and turn it so that you *just* can't see those blocks.
If the contrast is too low then you don't see the characters. If the contrast is too high then the 'blocks' hide the characters.
Susan

 

[FvM]

Seeing one line of blocks means that initialization of two line mode failed.

 

[betwixt]

Post # 3 ??
Add the delays as specified in the data sheet. You can't just 'rapid fire' all the initialization and data bytes without the required delay between them.

Brian.

 

[lucas_mur]

Post # 3 ??
Add the delays as specified in the data sheet. You can't just 'rapid fire' all the initialization and data bytes without the required delay between them.

Brian.

Sorry I forget to answer to your question. Actually I added the delay as specified in data sheet. I solved the problem. The problem was that LCD support just 5V not 3.3 V. So I changed the LCD with other that support 3.3V, I added delays and it works