In this post I’ll show how to connect and use a 16 x 2 LCD on a Raspberry Pi.

The LCD I am using is a Blue Character OLED(LCD) 16x2 from adafruit.

This display has ultra-high contrast and any-angle readability. It has the best display I have seen on any LCD.

This LCD uses the HD44780 controller which is present in almost all LCDs.
LCDs that use this controller usually have 14 or 16 pins. This LCD has 16, numbered from 0 to 16 as shown below.

Sometimes these pins are present, but not used. Eg, pins 15 & 16 are for back-light and they are not used on this LCD. It depends on the manufacture.

Wiring the LCD up

Below shows how to wire up the LCD to the Raspberry Pi. We will be using 4 pin mode, so there is no need to connect pins 7 to 10. This LCD doesn't use the backlight pins, pins 15 and 16. It also doesn't use the contrast pin, pin 3.

Code

In the past, you would have had to know the registers used by the controller to setup the display, position the cursor or even write a single character. There was also timing issues to take into consideration. This is no more, with thanks to WiringPi.

Installing WiringPi;

The code below is a very simple example of displaying some text on the top line of the LCD. There is a complete list of all the functions in the LCD library on the WiringPi website.

#include <wiringPi.h>           //WiringPi headers
#include <lcd.h>                //LCD headers from WiringPi
#include <stdio.h>              //Needed for the printf function below
//Pin numbers below are the WiringPi pin numbers
#define LCD_RS  3               //Register select pin
#define LCD_E   0               //Enable Pin
#define LCD_D4  6               //Data pin 4
#define LCD_D5  1               //Data pin 5
#define LCD_D6  5               //Data pin 6
#define LCD_D7  4               //Data pin 7
int main()
{
    int lcd;                //Handle for LCD
    wiringPiSetup();        //Initialise WiringPi
    //Initialise LCD(int rows, int cols, int bits, int rs, int enable, int d0, int d1, int d2, int d3, int d4, int d5, int d6, int d7)
    if (lcd = lcdInit (2, 16,4, LCD_RS, LCD_E ,LCD_D4 , LCD_D5, LCD_D6,LCD_D7,0,0,0,0)){
            printf ("lcdInit failed! \n");
            return -1 ;
    }
    lcdPosition(lcd,0,0);           //Position cursor on the first line in the first column
    lcdPuts(lcd, "Character LCD");  //Print the text on the LCD at the current cursor postion
    getchar();                      //Wait for key press
    lcdClear(lcd);                  //Clear the display
}

• Lines 1 and 2 are required as these are the headers for the WiringPi LCD library.
• Lines 7 to 12 are the definitions for the pins used to connect the LCD to the Raspberry Pi. Pin numbers can be found here.
• Line 21 will initialise the LCD with lcdInit()

The augments used in the lcdint() function are;
(int rows, int cols, int bits, int rs, int enable, int d0, int d1, int d2, int d3, int d4, int d5, int d6, int d7)
rows = Number of rows on the LCD
cols = Number of columns on the LCD
bits = Number of bits or data pins used. Either 8 or 4.
rs = Register select pin
enable = Enable pin
d0-d7 = 8 or 4 bit mode. In for 4 bit mode, only specificity pins from d0 to d3. If using 8 bit mode, you need to specify pins from d0 to d7. In the example code above, we are using 4 bit mode.

The code below is what was used in the video at the top of this post
Compile with;

#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <wiringPi.h>
#include <lcd.h>
#include <string.h>
#include <time.h>
char level0[8] = { 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b11111};
char level1[8] = { 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b11111, 0b11111};
char level2[8] = { 0b00000, 0b00000, 0b00000, 0b00000, 0b00000, 0b11111, 0b11111, 0b11111};
char level3[8] = { 0b00000, 0b00000, 0b00000, 0b00000, 0b11111, 0b11111, 0b11111, 0b11111};
char level4[8] = { 0b00000, 0b00000, 0b00000, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111};
char level5[8] = { 0b00000, 0b00000, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111};
char level6[8] = { 0b00000, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111};
char level7[8] = { 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111, 0b11111};
#define COLUMNS 16
#define LCD_RS  3
#define LCD_E   0
#define LCD_D4  6
#define LCD_D5  1
#define LCD_D6  5
#define LCD_D7  4
void uptime(void);
void memory(void);
void volume(void);
void scrollText(void);
void INThandler(int sig);
int mymillis(void);
char message[] = "WWW.OZZMAKER.COM";
int count =0;
int j = 0;
FILE *uptime_file, *mem_file;
char *temp;
int lcd;
int main()
{
        signal(SIGINT, INThandler);
        wiringPiSetup () ;
        if (lcd = lcdInit (2, 16,4, LCD_RS, LCD_E ,LCD_D4 , LCD_D5, LCD_D6,LCD_D7,0,0,0,0)){
                printf ("lcdInit failed! \n");
                 return -1 ;
        }
        int uptimeTimer;
        while(1){
                lcdClear (lcd);
                volume();
                sleep(1);
                memory();
                sleep(4);
                lcdClear (lcd);
                uptimeTimer  = mymillis();
                while ((mymillis() - uptimeTimer) < 5000)
                        uptime();
                sleep(1);
                lcdClear (lcd);
                scrollText();
        }
}
void uptime(void)
{
  unsigned int uptime_unsorted = 0;
  unsigned char c;
  unsigned int DD;
  unsigned int HH;
  unsigned int MM;
  unsigned int SS;
  uptime_file=fopen("/proc/uptime","r");
  if(NULL != uptime_file)
  {
    while((c=fgetc(uptime_file))!= '.')
      {
        unsigned int i;
        i = atoi(&c);
        uptime_unsorted = (uptime_unsorted * 10) + i;
      }
    SS = uptime_unsorted % 60;
    MM = uptime_unsorted / 60 % 60;
    HH = uptime_unsorted / 60 / 60 % 24;
    DD = uptime_unsorted / 60 / 60 / 24;
    printf("\x1B[2J");
    printf("Uptime:D%i,%02i:%02i:%02i\n",DD,HH,MM,SS);
    lcdPosition(lcd,0,0);
    lcdPrintf(lcd,"Uptime:  Days %i", DD);
    lcdPosition(lcd,4,1);
    lcdPrintf(lcd,"%02i:%02i:%02i",HH,MM,SS);
  }
  else
  {
    printf("Open file \"proc/uptime\" failed!\n");
  }
}
void memory(void)
{
   char MemTotal[35];
    char MemFree[35];
    char total[35];
    char free[35];
        lcdClear (lcd);
    mem_file=fopen("/proc/meminfo","r");
    if(NULL != mem_file)
    {
    fscanf(mem_file,"%*s%s%*s", MemTotal);
    fscanf(mem_file,"%*s%s%*s", MemFree);
    printf("\x1B[2J");
    lcdPosition(lcd,0,0);
    lcdPrintf(lcd,"MemTotal-%sk",MemTotal);
    lcdPosition(lcd,0,1);
    lcdPrintf(lcd,"MemFree -%sk",MemFree);
    fclose(mem_file);
  }
  else
  {
    printf("Open file \"/proc/meminfo\" failed!\n");
  }
}
void volume(void)
{
         //Defined custom characters for volume display
        lcdCharDef  (lcd, 0, level0);
        lcdCharDef  (lcd, 1, level1);
        lcdCharDef  (lcd, 2, level2);
        lcdCharDef  (lcd, 3, level3);
        lcdCharDef  (lcd, 4, level4);
        lcdCharDef  (lcd, 5, level5);
        lcdCharDef  (lcd, 6, level6);
        lcdCharDef  (lcd, 7, level7);
        lcdClear (lcd);
        int i;
        lcdPosition (lcd, 9,1);
        lcdPuts (lcd, ":Volume");
        for (i = 0; i < 7; i++){
                lcdPosition (lcd, i, 1);
                lcdPutchar  (lcd, i);
                usleep(400000);
        }
}
void  scrollText(void)
{
        int i,n;
        int h ;
        int tempSpace = 0;
        char scrollPadding[] = "                   ";
        int messageLength = strlen (scrollPadding)+strlen(message);
        for (n=0;n<messageLength;n++){ h = COLUMNS; usleep(300000); printf("\x1B[2J"); if ( j > messageLength )
                        j = 0;
                for (i = 0  ; i  < j ; i ++){
                        scrollPadding[h-j] = message[ i];
				h++;
                }
                lcdPosition(lcd,0,0);
                lcdClear (lcd);
                lcdPrintf(lcd,"%s",scrollPadding);
                j++;
        }
}
void  INThandler(int sig)
{
        lcdClear (lcd);
        fclose(uptime_file);
        signal(sig, SIG_IGN);
        exit(0);
}
int mymillis(void)
{
        struct timeval tv;
        gettimeofday(&tv, NULL);
        return (tv.tv_sec) * 1000 + (tv.tv_usec)/1000;
}

[wp_ad_camp_1]