2wireLCD

Table of Contents

    2-wire-LCD-Interface

    This is a 2-wire-LCD-interface, but not I2C.

    • Advantage:
    • You can use all pins to connect your LCD.
    • You don't need especially (I2C)IC.
    • high Refresh-Rate for the Display.(any MHz I2C only 400kHz)

    /media/uploads/elektronaut/lcd1.png

    • here is the programm: 

    #include "mbed.h"
#include "lcd_2wire.h"


lcd_2wire dis(p29,p30);
AnalogIn input(p20);
DigitalOut myled(LED1);

float wert;
char c[3];
int main() {
    dis.lcd_init();
    dis.lcd_goto_xy(0,0);
    dis.lcd_write_str("********************");
    dis.lcd_goto_xy(7,1);
    dis.lcd_write_str("Hallo");
    dis.lcd_goto_xy(7,2);
    dis.lcd_write_str("MBED!");
    dis.lcd_goto_xy(0,3);
    dis.lcd_write_str("********************");
    wait(2);
    
    
    while (1) {
        wert = input.read();
        sprintf(c,"%.3f",wert);
        dis.lcd_clear();
        dis.lcd_goto_xy(7,1);
        dis.lcd_write_str("Analogwert:");
        dis.lcd_goto_xy(7,2);
        dis.lcd_write_str(c);
        wait_ms(1);
        myled = 1;
        wait(0.1);
        myled = 0;
        wait(0.1);
    }
}
    • here is the necessary library: 

    #include "mbed.h"
#include "lcd_2wire.h"


lcd_2wire::lcd_2wire (PinName pinc, PinName pind ): _pinc(pinc),  _pind(pind) {
    _pinc = 0;//clock signal
    _pind = 0;// data signal
}
//-----------------------------
void lcd_2wire::LCD_SET_CLK(void) {
    _pinc = 1;
}
//---------------------------------
void lcd_2wire::LCD_CLR_CLK(void) {
    _pinc = 0;
}
//----------------------------------
void lcd_2wire::LCD_SET_DATA(void) {
    _pind = 1;
}
//----------------------------------
void lcd_2wire::LCD_CLR_DATA(void) {
    _pind = 0;
}
//----------------------------------
int LCD_ROW_TABLE[4] = {  //Display row addresses
    0x80,
    0xC0,
    0x80 + LCD_COLS,
    0xC0 + LCD_COLS
};
//----------------------------------------
void lcd_2wire::lcd_delay(void) { 
    wait_us(100);
}
//-------------------------------------------
void lcd_2wire::lcd_init_shift_reg(int mode) {   //Clear shift register, set E and RS
    int n;

    LCD_CLR_DATA(); //clear data signal
    lcd_delay();

//clear all outputs of shift register
    for (n=7; n; n--) {
        LCD_SET_CLK();
        lcd_delay();
        LCD_CLR_CLK();
    }

//Set high level for E at Q7
    LCD_SET_DATA();
    lcd_delay();
    LCD_SET_CLK();
    lcd_delay();
    LCD_CLR_CLK();

//Set level for RS at Q6
    if (mode == LCD_DATA_MODE) {
        LCD_SET_DATA();
    } else {
        LCD_CLR_DATA();
    }
    lcd_delay();
    LCD_SET_CLK();
    lcd_delay();
    LCD_CLR_CLK();
}
//----------------------------------------------
void lcd_2wire::lcd_shift_nibble(int data) { //Clock in 4 bits of data
    int n, mask= 0x08;
    for (n =4; n; n--) {   //do this for 4 databits
        if (data & mask) {  // set or reset data signal
            LCD_SET_DATA();
        } else {
            LCD_CLR_DATA();
        }
        LCD_SET_CLK();
        lcd_delay();
        LCD_CLR_CLK();
        mask >>= 1;  // shift right
    }
    LCD_SET_CLK();
    lcd_delay();
    LCD_CLR_CLK();
}
//-------------------------------------------------

void lcd_2wire::lcd_shift_byte(int data , int mode) {
    lcd_init_shift_reg(mode);
    lcd_shift_nibble(data >> 4);
    LCD_SET_DATA();
    lcd_delay();
    if (mode != LCD_INIT_MODE) {
        lcd_init_shift_reg(mode);
        lcd_shift_nibble(data);
        LCD_SET_DATA();
        lcd_delay();
    }
    LCD_CLR_DATA();
    lcd_delay();
}
//-------------------------------------------------
void lcd_2wire::lcd_write_command(int command) {
    lcd_shift_byte(command,LCD_CMD_MODE);
}
//---------------------------------------------------
void lcd_2wire::lcd_write_data(int data) {
    lcd_shift_byte(data,LCD_DATA_MODE);
}
//----------------------------------------------
//Functions flags - Bit 0  0: 5x7 Dots   1:5x10 Dots
//                  Bit 1  0: 1 Row      1: 2 Rows
//                  Bit 2  0: 4-Bit Intf 1: 8-Bit Intf
void lcd_2wire::lcd_function_mode(int function_mode) {
    function_mode =((function_mode & 7) << 2) + 0x20;
    lcd_write_command(function_mode);
}
//-------------------------------------------------
void lcd_2wire::lcd_display_mode(int display_mode) {
    display_mode =(display_mode & 7) + 0x08;
    lcd_write_command(display_mode);
}
//-------------------------------------------------
void lcd_2wire::lcd_entry_mode(int entry_mode) {
    entry_mode =(entry_mode & 3) + 0x04;
    lcd_write_command(entry_mode);
}
//-------------------------------------------------
void lcd_2wire::lcd_clear(void) {
    lcd_write_command(LCD_CLR);
}
//--------------------------------------------------
void lcd_2wire::lcd_home(void) {
    lcd_write_command(LCD_HOME);
}
//--------------------------------------------------
void lcd_2wire::lcd_goto_xy(int xpos, int ypos) {
    if (xpos < LCD_COLS && ypos <LCD_ROWS) {
        lcd_write_command(LCD_ROW_TABLE[ypos] + xpos);
    }
}
//---------------------------------------------------
void lcd_2wire::lcd_write_char(int chr) {
    lcd_write_data(chr);
}
//--------------------------------------------------
void lcd_2wire::lcd_write_char_xy(int x, int y, int chr) {
    lcd_goto_xy(x,y);
    lcd_write_data(chr);
}
//------------------------------------------------
void lcd_2wire::lcd_write_str(const char *sp) {
    while (*sp) {
        lcd_write_data(*sp++);
    }
}
//----------------------------------------------------
void lcd_2wire::lcd_write_str_xy(int x, int y, const char *sp) {
    lcd_goto_xy(x,y);
    lcd_write_data(*sp++);
}
//----------------------------------------------------
void lcd_2wire::lcd_init(void) {
    LCD_CLR_CLK();
    LCD_CLR_DATA();

    wait_ms(LCD_POWER_UP_DELAY_MS);

//Startinitialisation

    lcd_shift_byte(LCD_FUNCTION_8BIT_1LINE,LCD_INIT_MODE);
    wait_ms(LCD_INIT_DELAY_MS);
    lcd_shift_byte(LCD_FUNCTION_8BIT_1LINE,LCD_INIT_MODE);
    wait_ms(LCD_INIT_DELAY_MS);
    lcd_shift_byte(LCD_FUNCTION_8BIT_1LINE,LCD_INIT_MODE);
    wait_ms(LCD_INIT_DELAY_MS);
    lcd_shift_byte(LCD_FUNCTION_4BIT_1LINE,LCD_INIT_MODE);
    wait_ms(LCD_INIT_DELAY_MS);
//Display is in 4 bit I/O mode now
#if (LCD_ROWS > 1)
    lcd_write_command(LCD_FUNCTION_4BIT_2LINE);
#else
    lcd_write_command(LCD_FUNCTION_4BIT_1LINE);
#endif
    wait_ms(LCD_INIT_DELAY_MS);
    lcd_write_command(LCD_DISP_ON);
    wait_ms(LCD_INIT_DELAY_MS);
    lcd_write_command(LCD_CLR);
    lcd_write_command(LCD_HOME);
    wait_ms(LCD_INIT_DELAY_MS);
}
    • and the header 

    #ifndef MBED_LCD_2WIRE_H
#define MBED_LCD_2WIRE_H

#include "mbed.h"

class lcd_2wire {
public:
    lcd_2wire(PinName pinc, PinName pind);

#define LCD_CMD_MODE 0
#define LCD_DATA_MODE 1
#define LCD_INIT_MODE 2
#define LCD_CLR 1
#define LCD_HOME 2
#define LCD_DISP_ON 0x0C
#define LCD_FUNCTION_4BIT_1LINE 0x20
#define LCD_FUNCTION_4BIT_2LINE 0x28
#define LCD_FUNCTION_8BIT_1LINE 0x30
#define LCD_FUNCTION_8BIT_2LINE 0x38
#define LCD_COLS 20
#define LCD_ROWS 4
#define LCD_POWER_UP_DELAY_MS 50
#define LCD_INIT_DELAY_MS 5


    void lcd_init(void);
    void lcd_clear();
    void lcd_home(void);
    void lcd_goto_xy(int xpos, int ypos);
    void lcd_write_char(int chr);
    void lcd_write_char_xy(int x, int y, int chr);
    void lcd_write_str(const char *sp);
    void lcd_write_str_xy(int x,int y,const char *sp);

private:
    DigitalOut _pinc;
    DigitalOut _pind;
    void LCD_SET_CLK();
    void LCD_CLR_CLK();
    void LCD_SET_DATA();
    void LCD_CLR_DATA();
    void lcd_delay();
    void lcd_init_shift_reg(int mode);
    void lcd_shift_nibble(int data);
    void lcd_shift_byte(int data, int mode);
    void lcd_write_command(int command);
    void lcd_write_data(int data);
    void lcd_function_mode(int function_mode);
    void lcd_display_mode(int display_mode);
    void lcd_entry_mode(int entry_mode);
};
#endif
    • to the end any photos /media/uploads/elektronaut/photmbed.jpg /media/uploads/elektronaut/photplah.jpg
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