Re^3: i2c attached LCD Character Display for a Raspberry Pi

anita2R

I went back and looked at my chipKIT code. Turns out my Sparkfun LCD is a SPI interface. My SF 4 digit LED display uses I2C. In either case neither required any bit twiddling. Their backpack has an on-board PIC that abstracts out the HD44780 handling. Ease of use and no soldering comes at a higher price(double) than you have with the SainSmart product.

Update:I read through the HiPi docs last night. Good stuff! The developer, Mark Dootson, has done much work on wxPerl and I believe that wxPerl will run on the RPI, if you need to do any GUI work.

For Example:

// SerLCDTest.pde - Serial Interface Version for use with the chipKIT 
+UNO
//
// This display uses the HD44780 LCD controller and a PIC16F688 serial
+ interface
//
// Test file for the Sparkfun Serial LCD used with the chipKIT UNO
//    Uses UART1(pin 40 TX) so UART0/USB can be used for debug message
+s
//    Combined header and library files for initial testing of the dis
+play.
//    Hope to split into a library after testing.
//
// James M. Lynes, Jr.
// Last Modified: December 24,2012
//
// This code is public domain, but you buy me a beer(or Dr. Pepper)
// if you use this and we meet some day(Beerware License).
//
// Constant Definitions
//
// Display Commands
//
#define    COMMAND        0xFE        // Command Code
#define    CLEARDISP    0x01        // Clear the display
#define    CURSORHOME    0x02        // Send the cursor home
#define    CURSORRIGHT    0x14        // Move the cursor right one pos
+ition
#define    CURSORLEFT    0x10        // Move cursor left one position
#define    SCROLLRIGHT    0x1C        // Scroll the display right
#define    SCROLLLEFT    0x18        // Scroll the display left
#define    DISPLAYON    0x0C        // Turn the display on
#define DISPLAYOFF    0x08        // Turn the display off
#define    UCURSORON    0x0E        // Turn underline cursor on
#define UCURSOROFF    0x0C        // Turn underline cursor off
#define    BOXCURSORON    0x0D        // Turn box cursor on
#define    BOXCURSOROFF    0x0C        // Turn box cursor off
#define    LINE1        0x80        // Row 1 COl 1 Address
#define    LINE2        0xC0        // Row 2 COl 1 Address
#define    RESET        0x12        // Reset code, send at 9600 baud i
+mmediately after POR
//
// Configuration Commands
//
#define    CONFIG        0x7C        // Configuration Code
#define    B2400        0x0B        // Set 2400  baud
#define B4800        0x0C        // Set 4800  baud
#define    B9600        0x0D        // Set 9600  baud
#define B144K        0x0E        // Set 14400 baud
#define    B192K        0x0F        // Set 19200 baud
#define B384K        0x10        // Set 38400 baud
#define SAVESPLASH    0x0A        // Save a new splash message
#define    TOGGLESPLASH    0x09        // Toggle splash screen on and 
+off
#define    BACKLIGHTOFF    0x80        // Turn the backlight off
#define    BACKLIGHTMED    0x8F        // Turn the backlight to 50%
#define BACKLIGHTHIGH    0x9D        // Turn the backlight to 100%
//
// Misc Defines
//
#define    LCDTYPE        0x03        // Type 2 line x 16 characters
#define    LCDDelay    0x10        // General delay timer
#define    LCDDelay2    0x200        // Scroll timer
//
// Function Protypes
//
void    LCDClear();            // Clear the display
void    LCDSelectLineOne();        // Position cursor to the beginning
+ of line 1
void    LCDSelectLineTwo();        // Position cursor to the beginning
+ of Line 2
void    LCDGoTo(int position);        // Position cursor to a specific
+ character 0-15, 16-31
void    LCDBacklightOn();        // Turn the backlight on
void    LCDBacklightOff();        // Turn the backlight off
void    LCDCursorHome();        // Position cursor to home
void    LCDCursorRight();        // Set cursor to move left to rght
void    LCDCursorLeft();        // Set cursor to move right to left
void    LCDScrollRight();        // Scroll the display right
void    LCDScrollLeft();        // Scroll the dispaly left
void    LCDDisplayOn();            // Turn the display on
void    LCDDisplayOff();        // Turn the display off
void    LCDUCursorOn();            // Turn the underline cursor on
void    LCDUCursorOff();        // Turn the underline cursor off
void    LCDBoxCursorOn();        // Turn the box cursor on
void    LCDBoxCursorOff();        // Turn the box cousor off
void    LCDBlackStart();        // Restart from an unknown state
void    LCDSaveSplash(char*, char*);    // Save a new spash display
void    LCDToggleSplash();        // Toggle the splash display on/off/
+on
void    LCDSetBrightness(int);        // Set the screen brightness 128
+-157(0x80-0x9D)
void    LCDSetBaud(int);        // Set a new baud rate
//
// Test Function Prototypes
//
void    tstwrite();            // Write out two lines of text
void    tstmoves();            // Try some cursor moves
void    tstscroll();            // Try some scrolling
void    tstbrightness();        // Cycle the backlight high to off
//
// Main Program
//
void    setup()
{
    delay(3000);            // Time to allow the splash screen to disp
+lay
    Serial.begin(9600);        // Start serial communications for debu
+g messages
    Serial.println("Initialized UNO Serial/USB Port");
    Serial1.begin(9600);        // Initialize the UART1 hardware
    Serial.println("Initialized UNO UART1");
    LCDClear();            // Reset the LED display, cursor to positio
+n 1
    Serial.println("Cleared the LCD Display");
    LCDSetBrightness(BACKLIGHTHIGH);// Set display to max brightness
}

void loop()
{
    Serial.println("Mainloop");
    Serial.println("Writes");
    tstwrite();
    delay(2000);
    Serial.println("Moves");
    tstmoves();
    delay(10000);
    Serial.println("Scrolls");
    tstscroll();
    delay(2000);
//    Serial.println("Brightness");
//    tstbrightness();
//    delay(2000);
}

// Test Subroutines

void    tstwrite()
{
    LCDClear();
    LCDSelectLineOne();
    Serial1.print("Merry Christmas");
    LCDSelectLineTwo();
    Serial1.print(" to my Sweetie ");
}

void    tstmoves()
{
    LCDClear();
    LCDSelectLineOne();
    Serial1.print("789ABCDEF6543210");
    LCDSelectLineTwo();
    LCDGoTo(24);
    Serial1.print("@");
    LCDCursorRight();
    LCDCursorRight();
    Serial1.print("#");
    LCDCursorHome();
    Serial1.print("$");
    LCDCursorHome();
    LCDCursorLeft();
//    LCDCursorLeft();
    Serial1.print("%");
}

void    tstscroll()
{
    LCDClear();
    LCDSelectLineOne();
    Serial1.print("0123456789ABCDEF");
    delay(LCDDelay);
    for(int i=1 ; i<9; i++){
        LCDScrollLeft();
    }
    for(int i=1 ; i<9; i++){
        LCDScrollRight();
    }
}

void    tstbrightness()
{
    tstwrite();
    LCDSetBrightness(BACKLIGHTHIGH);
    LCDSetBrightness(BACKLIGHTMED);
    LCDSetBrightness(BACKLIGHTOFF);
}

// Library Subroutines

void    LCDClear()
{
    Serial1.write(COMMAND);
    Serial1.write(CLEARDISP);        // Clear the display
    delay(LCDDelay);
}

void    LCDSelectLineOne()
{
    Serial1.write(COMMAND);
    Serial1.write(LINE1);            // Select line 1
    delay(LCDDelay);    
}

void    LCDSelectLineTwo()
{
    Serial1.write(COMMAND);
    Serial1.write(LINE2);            // Select line 2
    delay(LCDDelay);
}

void    LCDGoTo(int position)
{
    if(position < 16)            // Go to specific position 0-31
    {
        Serial1.write(COMMAND);
        Serial1.write(position + 128);
    }
    else if(position < 32)
    {
        Serial1.write(COMMAND);
        Serial1.write(position + 48 + 128);
    }
    else
    {
        LCDGoTo(0);
    }
    delay(LCDDelay);
}

void    LCDBacklightOn()
{
    Serial1.write(CONFIG);
    Serial1.write(BACKLIGHTHIGH);        // Turn the backlight on
    delay(LCDDelay);
}

void    LCDBacklightOff()
{
    Serial1.write(CONFIG);
    Serial1.write(BACKLIGHTOFF);        // Turn the backlight off
    delay(LCDDelay);
}

void    LCDCursorHome()
{
    Serial1.write(COMMAND);
    Serial1.write(CURSORHOME);        // Position the cursor to home
    delay(LCDDelay);
}

void    LCDCursorRight()
{
    Serial1.write(COMMAND);
    Serial1.write(CURSORRIGHT);        // Move cursor right one positi
+on
    delay(LCDDelay);
}

void    LCDCursorLeft()
{
    Serial1.write(COMMAND);
    Serial1.write(CURSORLEFT);        // Move cursor left one position
    delay(LCDDelay);
}

void    LCDScrollRight()
{
    Serial1.write(COMMAND);
    Serial1.write(SCROLLRIGHT);        // Scroll the display right one
+ position
    delay(LCDDelay2);
}

void    LCDScrollLeft()
{
    Serial1.write(COMMAND);
    Serial1.write(SCROLLLEFT);        // Scroll the display left one p
+osition
    delay(LCDDelay2);
}

void    LCDDisplayOn()
{
    Serial1.write(COMMAND);
    Serial1.write(DISPLAYON);        // Turn the display on
    delay(LCDDelay);
}

void    LCDDisplayOff()
{
    Serial1.write(COMMAND);
    Serial1.write(DISPLAYOFF);        // Turn the display off
    delay(LCDDelay);
}

void    LCDUCursorOn()
{
    Serial1.write(COMMAND);
    Serial1.write(UCURSORON);        // Turn the underline cursor on
    delay(LCDDelay);
}

void    LCDUCursorOff()
{
    Serial1.write(COMMAND);
    Serial1.write(UCURSOROFF);        // Turn the underline cursor off
    delay(LCDDelay);
}

void    LCDBoxCursorOn()
{
    Serial1.write(COMMAND);
    Serial1.write(BOXCURSORON);        // Turn the box cursor on
    delay(LCDDelay);
}

void    LCDBoxCursorOff()
{
    Serial1.write(COMMAND);
    Serial1.write(BOXCURSOROFF);        // Turn the box cursor off
    delay(LCDDelay);
}

void    LCDBlackStart()
{
    Serial1.write(RESET);            // Restart from unknown condition
    delay(LCDDelay);
}

void    LCDSaveSplash(char *l1, char *l2)
{
    LCDSelectLineOne();            // Replace the splash screen
    Serial1.print(l1);
    LCDSelectLineTwo();
    Serial1.print(l2);
    Serial1.write(CONFIG);
    Serial1.write(SAVESPLASH);
    delay(LCDDelay);
}

void    LCDToggleSplash()
{
    Serial1.write(CONFIG);            // Toggle the splash screen on/o
+ff/on
    Serial1.write(TOGGLESPLASH);
    delay(LCDDelay);
}

void    LCDSetBrightness(int level)
{
    Serial1.write(CONFIG);            // Change the brightness level
    Serial1.write(level);
    delay(LCDDelay);
}

void    LCDSetBaud(int rate)
{
    Serial1.write(CONFIG);            // Change the baud rate
    Serial1.write(rate);
    delay(LCDDelay);
}
[download]

James

There's never enough time to do it right, but always enough time to do it over...

Comment on Re^3: i2c attached LCD Character Display for a Raspberry Pi Download Code

Replies are listed 'Best First'.

Re^4: i2c attached LCD Character Display for a Raspberry Pi
by Anonymous Monk on Feb 25, 2017 at 16:58 UTC

This code uses the HiPi module which seemed to me to require I load the whole GUI (I am using minibian) so I converted a Python demo program to Perl as an illustration of how to use the SMBus module to write to an I2C LCD (16x2). Here is the code:

#!/usr/bin/perl
# Example program which writes to the I2C LCD at address 0x3f.  This w
+as 
# a direct port of the program published by Matt Hawkins on the site
# www.raspberrypi-spy.co.uk.  Port performed by Steve Stock.   
#
use strict;
use warnings;
use Time::HiRes ('usleep');
use Device::SMBus;

my $I2C_ADDR=0x3f;
my $DEVICE_PATH = '/dev/i2c-1';
my $dev = Device::SMBus->new(I2CBusDevicePath => $DEVICE_PATH,
  I2CDeviceAddress => $I2C_ADDR);
my $LCD_WIDTH = 16;
my $LCD_CHR=1;
my $LCD_CMD=0;
my $FILL_CHAR=" ";

my $LCD_LINE_1=0x80;
my $LCD_LINE_2=0xc0;
my $LCD_LINE_3=0x94;
my $LCD_LINE_4=0xd4;

my $LCD_BACKLIGHT=0x08;
my $LCD_BACKLIGHT_OFF=0x00;

my $ENABLE=0b00000100;

my $E_PULSE=500;
my $E_DELAY=500;

sub lcd_toggle_enable {
  my ($bits)=@_;
  usleep($E_PULSE);
  my $rc = $dev->writeByteData(0x00,$bits | $ENABLE);
  $rc = $dev->writeByteData(0x00,$bits & ~$ENABLE);
}


sub lcd_byte {
  my ($bits,$mode) = @_;
  my $bits_high=0;my $bits_low=0;
  $bits_high = $mode | ($bits & 0xf0) | $LCD_BACKLIGHT;
  $bits_low = $mode | (($bits << 4) & 0xf0) | $LCD_BACKLIGHT;
  my $rc = $dev->writeByteData(0x00,$bits_high);  
  lcd_toggle_enable($bits_high);
  $rc = $dev->writeByteData(0x00,$bits_low);
  lcd_toggle_enable($bits_low);
  usleep($E_PULSE);
}

sub lcd_init {
  lcd_byte(0x33,$LCD_CMD);
  lcd_byte(0x32,$LCD_CMD);
  lcd_byte(0x06,$LCD_CMD);
  lcd_byte(0x0c,$LCD_CMD);
  lcd_byte(0x28,$LCD_CMD);
  lcd_byte(0x01,$LCD_CMD);
  usleep($E_PULSE);
}

sub lcd_string {
  my ($message, $line) = @_;
  lcd_byte($line, $LCD_CMD);
  for (0..$LCD_WIDTH) {$message=$message.$FILL_CHAR};
  for (my $i=0;$i<($LCD_WIDTH);$i++) {lcd_byte(ord(substr($message,$i,
+1)),$LCD_CHR);}
}  

# MAIN
while (1==1) {
  lcd_init(); 
  lcd_string("RPiSpy         <",$LCD_LINE_1);
  lcd_string("I2C LCD        <",$LCD_LINE_2);
  sleep(5);
  lcd_string(">         RPiSpy",$LCD_LINE_1);
  lcd_string(">        I2C LCD",$LCD_LINE_2);
  sleep(5);
}
[download]

[reply]
[d/l]


Perl Monk, Perl Meditation
	PerlMonks