STM32f4与LCD16x2的接口

Question

I write program interface STM32F411vet6 with LCD 16x2 text but when I deliver code to kit it doesn't run. Can someone check my code and find error please? Thank you so much!

Describe:

• void ENEable(void): Wait microsecond to RS pin can receive command.

• void WriteNibble(int8_t data, int8_t flag): Write high nibble(flag = 0) and low nibble(flag = 1)

• void LCDCmd(int8_t cmd): Require KIT run command

• void LCDInit(void): initialize LCD.

Code LCD 16x2:

void ENEable(void)
{
    HIGH_PIN(EN_PIN);
    DelayMicros(5);
    LOW_PIN(EN_PIN);
    DelayMicros(100);
}

void WriteNibble(int8_t data, int8_t flag)
{
    flag = 4 * flag;
    if(data & (0x80 >> flag))
    {
        HIGH_PIN(D7_PIN);
    }
    else
    {
        LOW_PIN(D7_PIN);
    }

    if(data & (0x40 >> flag))
    {
        HIGH_PIN(D6_PIN);
    }
    else
    {
        LOW_PIN(D6_PIN);
    }

    if(data & (0x20 >> flag))
    {
        HIGH_PIN(D5_PIN);
    }
    else
    {
        LOW_PIN(D5_PIN);
    }

    if(data & (0x10 >> flag))
    {
        HIGH_PIN(D4_PIN);
    }
    else
    {
        LOW_PIN(D4_PIN);
    }
}

void LCDCmd(int8_t cmd)
{
    LOW_PIN(RS_PIN);
    DelayMicros(100);

    WriteNibble(cmd, 0);
    ENEable();
    WriteNibble(cmd, 1);
    ENEable();

    switch(cmd){
        case 0x01:
        case 0x02: 
            DelayMilis(2);
            DelayMicros(250);
            break;
        default:
            DelayMicros(53);
            break;
    }
}

void LCDInit(void)
{
    DelayMilis(15);

    LCDCmd(0x03);
    ENEable();

    DelayMilis(4); //delay 4.1 milisencond
    DelayMicros(100);

    LCDCmd(0x03);
    ENEable();
    DelayMicros(100); //delay 100 microsecond

    LCDCmd(0x03);
    ENEable();
    DelayMicros(100); //delay 100 microsecond

    LCDCmd(0x02);
    ENEable();
    DelayMicros(100); //delay 100 microsecond

    LCDCmd(0x28); // use control: 4 bit, 2 line, 5x8;
    LCDCmd(0x0F); // turn on display, setting, cusor blink
    LCDCmd(0x01); // clear lcd
    LCDCmd(0x06); // set entry mode
}

void SendData(int8_t data)
{
    HIGH_PIN(RS_PIN);
    DelayMicros(5);

    WriteNibble(data, 0);
    ENEable();
    WriteNibble(data, 1);
    ENEable();
}

Delay function:

Describe:

void DelayMicros(uint32_t timer): Delay micro second
void DelayMilis(uint32_t timer): Delay mili second

void DelayMicros(uint32_t timer)
{
    uint32_t count = 0;

    while(timer--)
    {
        count = SystemCoreClock / 1000 / 1000 / 4;
        while(count--);
    }
}

void DelayMilis(uint32_t timer)
{
    uint32_t count = 0;

    while(timer--)
    {
        count = SystemCoreClock / 1000 / 4;
        while(count--);
    }
}

I searched the Internet but I couldn't find the reason. I am newbie.

Thank you! Have a nice day!

Answer 1

Did you check the contrast?

Remember that the LCD 16x2 has a pin that adjusts the contrast (pin 3). You should vary the voltage at this pin between 0 to Vcc until you see something in the LCD.

Othewise...

If this is not the case there are so many things that can go wrong when working on the classic 16x2 LCDs. Bad contact in the pins, inadequate Vcc, bugs in the timing or the correct bit to set. It is hard to tell without the board in the hands. I had to bang my head against the wall for days to get it working the first time, and it was not in the first attempt. I wish you good luck.