LCD_IO 8 Example

This is an connection mode 8 Driver to demonstrate LCD features. This for the 16F877A, but, it can easily be adapted for other microcontrollers.

A 2 by 16 LCD is assumed.

Based on the works by Thomas Henry and then revised Evan R. Venn

    #chip 16F877A,20


    'Use LCD in 8 pin mode and define LCD pins
    #define LCD_IO 8
    #define LCD_RW PORTE.1
    #define LCD_RS PORTE.0
    #define LCD_Enable PORTE.2
    #define LCD_Data_Port PORTD

    ;Here are various LCD commands which can be used.
    ;These are the LCD commands for the HD44780 controller
    #define clrHome = 1     ;clear the display, home the cursor
    #define home    = 2     ;home the cursor only
    #define RtoL    = 4     ;print characters right to left
    #define insR    = 5     ;insert characters to right
    #define LtoR    = 6     ;print characters left to right
    #define insL    = 7     ;insert characters to left
    #define lcdOff  = 8     ;LCD screen off
    #define lcdOn   = 12    ;LCD screen on, no cursor
    #define curOff  = 12    ;an alias for the above
    #define block   = 13    ;LCD screen on, block cursor
    #define under   = 14    ;LCD screen on, underline cursor
    #define undblk  = 15    ;LCD screen on, blinking and underline cursor
    #define CLeft   = 16    ;cursor left
    #define CRight  = 20    ;cursor right
    #define panR    = 24    ;pan viewing window right
    #define panL    = 28    ;pan viewing window left
    #define bus4    = 32    ;4-bit data bus mode
    #define bus8    = 48    ;8-bit data bus mode
    #define mode1   = 32    ;one-line mode (alias)
    #define mode2   = 40    ;two-line mode
    #define line1   = 128   ;go to start of line 1
    #define line2   = 192   ;go to start of line 2
    ;----- Variables
    dim char, msn, lsn, index, ii as byte
    ;----- Main Program
    LoadEeprom              ;load the EEprom with strings

    do forever
        printMsg(0)             ;print first message
        wait 3 S                ;pause 3 seconds
        printMsg(2)             ;print next message
        wait 3 S                ;pause 3 seconds
        repeat 5                ;blink it five times
          LCDCmd(lcdOff)       ;display off
          wait 500 mS           ;pause
          LCDCmd(lcdOn)        ;display on
          wait 500 mS           ;pause
        end repeat
        wait 1 S                ;pause before next demo
        ;demonstrate panning
        printMsg(4)             ;print next message
        wait 3 S                ;pause 3 seconds
        repeat 16
          LCDCmd(panL)         ;pan left a step at a time
          wait 300 mS           ;slow down to avoid blur
        end repeat
        repeat 16
          LCDCmd(panR)         ;then pan right
          wait 300 mS
        end repeat
        wait 1 S                ;pause before next demo
                                ;demonstrate moving the cursor
        printMsg(6)             ;print next message
        wait 3 S                ;pause 3 seconds
        doHome                  ;home cursor
        LCDCmd(under)          ;choose underline cursor
        for ii = 0 to 15         ;move cursor across first line
          LCDCmd(line1+i)
          wait 200 mS
        next i
        for ii = 0 to 15         ;move cursor across second line
          LCDCmd(line2+i)
          wait 200 mS
        next i
        for ii = 15 to 0 step -1 ;move cursor back over second line
          LCDCmd(line2+i)
          wait 200 mS
        next i
        for ii = 15 to 0 step -1 ;move cursor back over first line
          LCDCmd(line1+i)
          wait 200 mS
        next i
        wait 3 S
        ;demonstrate blinking block cursor
        printMsg(8)             ;print next message
        doHome                  ;home the cursor
        LCDCmd(block)          ;choose blinking block cursor
        wait 4 S                ;pause 4 seconds
        LCDCmd(mode1)          ;change to one long line mode
        doHome                  ;home the cursor again
        LCDCmd(curOff)         ;and disable it


        ;demonstrate scrolling a lengthy one-line marquee
        for ii = 0xd0 to 0xff    ;print next message - the remaining EEPROM
          EPread ii, char        ;fetch directly from eeprom
          print chr(char)
        next i
        wait 1 S
        doHome                  ;home cursor once more
        repeat 141              ;scroll message twice
          LCDCmd(panR)
          wait 250 mS
        end repeat
        wait 2 S
        LCDCmd(mode2)          ;change back to two line mode
        doClr                   ;clear the screen
        ;demonstrate all of the characters
        printMsg(11)             ;print next message
        for ii = 33 to 127       ;print first batch of ASCII characters
          LCDCmd(line1+12)     ;overwrite each character displayed
          print chr(ii)            ;this is the ASCII code
          wait 500 mS
        next i
        for ii = 161 to 255      ;print next batch of ASCII characters
          LCDCmd(line1+12)
          print chr(ii)
          wait 500 mS
        next i
        ;say good-bye
        LCDCmd(line2)
        printMsg(11)             ;print next message
        doHome                  ;home the cursor
    loop
    end

    ;----- Clear the screen
    sub doClr
        LCDCmd(clrHome)
        wait 5 mS                   ;this command takes extra time
    end sub

    ;----- Home the cursor
    sub doHome
        LCDCmd(home)
        wait 5 mS                   ;and so does this one
    end sub

    ;----- Print a message to the LCD
    ;The parameter 'row' points to the start of the string.
    sub printMsg(in row as byte, in Optional StringLength As Byte = 15)
          LCDCmd(line1)              ;get set for first line

          for ii = 0 to StringLength
            index = row*16+ii
            EPread index, char        ;fetch next character and
            print chr(char)             ;transmit to the LCD
          next
          LCDCmd(line2)              ;get set for second line
          for ii = 0 to StringLength
            index = (row+1)*16+ii
            EPread index, char        ;fetch next character and
            print chr(char)             ;transmit to the LCD
          next
    end sub

    sub loadEeprom

        ' Strings for EEPROM, Strings should be limited to 16 characters for the first 13 sstrings, then a long string to fill eeprom
        location = 0
        WriteEeprom "First we'll show"
        WriteEeprom "this message.   "
        WriteEeprom "Then we'll blink"
        WriteEeprom "five times.     "
        WriteEeprom "Now lets pan    "
        WriteEeprom "left and right. "
        WriteEeprom "Watch the line  "
        WriteEeprom "cursor move.    "
        WriteEeprom "A block cursor  "
        WriteEeprom "is available.   "
        WriteEeprom "Characters:     "
        WriteEeprom "Bye!            "
        WriteEeprom "in one line mode"
        WriteEeprom "Next well scroll this long message as a marquee"
    end sub


    ; Write to the device eeprom
    sub WriteEeprom ( in Estring() ) as string * 64
        for ee = 1 to len ( Estring )
            HSersend Estring(ee)
            epwrite location, Estring(ee)
            location++
        next
    end sub