In case anyone is interested here is a display driver I developed for a
project
I am working on. The code is placed in the public domain so use it anyway
you want.
Cheers !
\ LCD 16x2 Display Driver for Arduino Uno
\ Based on Hitachi HD44780 Controller
\ Written for AmForth
\ By: Craig A. Lindley
\ Last Update: 11/25/2013
\ Must have bitnames.frt and marker.frt loaded
\ Uses 4 bit data interface with the following connections
\
\ LCD Pin Number LCD Signal Name Arduino Pin Number Arduino Signal
Name
\ 1 Gnd Gnd Gnd
\ 2 5V 5V 5V
\ 3 Vl Arm of 10K pot connected between 5V and Gnd
\ 4 RS 8 PortB Pin 0
\ 5 RW This signal connected to Gnd (no reading
possible)
\ 6 EN 9 PortB Pin 1
\ 11 D4 10 PortB Pin 2
\ 12 D5 11 PortB Pin 3
\ 13 D6 12 PortB Pin 4
\ 14 D7 13 PortB Pin 5
\ 15 +LED (backlight) 3 PortD Pin 3
\ 16 -LED This signal connected to Gnd
marker _LCD_
\ Port and Bit definitions
\ PORTB
&37 constant PORTB \ Port B Data Register
&36 constant DDRB \ Port B Data Direction Register
\ PORTD
&43 constant PORTD \ Port D Data Register
&42 constant DDRD \ Port D Data Direction Register
\ Control line definitions
PORTB 0 portpin: rs \ High to set data : Low to set command/control
PORTB 1 portpin: en \ Enable strobe is active low
PORTD 3 portpin: bl \ Backlight control
\ Write 4 data bits
: write4Bits ( data --- )
$000F and
2 lshift
PORTB c@
$03 and or
PORTB c!
\ Pulse en low - high - low
en low
en high
en low
;
\ Write 8 bit data to the LCD
: doIO ( data --- )
$FF and ( data --- )
dup ( data --- data data )
4 rshift
write4Bits \ Most significant 4 bits
write4Bits \ Least significant 4 bits
;
\ Write data to the LCD
: writeData
rs high
doIO
;
\ Write command to the LCD
: writeCommand
rs low
doIO
;
variable displayControl
\ Clear display
: clearDisplay
$01 writeCommand
2 ms \ This command takes a while
;
\ Home display
: homeDisplay
$02 writeCommand
2 ms \ This command takes a while
;
\ Display On/Off
: displayMode ( f --- )
if
displayControl @ $04 or displayControl !
else
displayControl @ $FB and displayControl !
then
displayControl @ writeCommand
;
\ Cursor On/Off
: cursorMode ( f --- )
if
displayControl @ $02 or displayControl !
else
displayControl @ $FD and displayControl !
then
displayControl @ writeCommand
;
\ Blink On/Off
: blinkMode ( f --- )
if
displayControl @ $01 or displayControl !
else
displayControl @ $FE and displayControl !
then
displayControl @ writeCommand
;
\ Set the position at which the next char will be written
: setCharPosition ( col row --- )
dup ( col row --- col row row )
\ Row must be 0 or 1
0 2 within ( col row row --- col row f )
rot dup ( col row f --- row f col col )
\ Col must be between 0 and 15
0 16 within ( row f col col --- row f col f )
rot ( row f col f --- row col f f )
and ( row col f f --- row col f )
if ( row col f --- row col )
swap ( row col --- col row )
$40 * +
$80 or
writeCommand
else
drop drop
then
;
\ Scroll display left
: scrollLeft
$18 writeCommand
;
\ Scroll display right
: scrollRight
$1C writeCommand
;
\ Initialize the LCD display for 4 bit operation
: initLCD
\ Set output bit direction
$3F DDRB c! \ 6 bits of PORTB to output
$FF DDRD c! \ 8 bits of PORTD to output
$00 PORTB c! \ All bits low
$00 PORTD c! \ All bits low
50 ms
\ Set the control bits for writing commands
rs low
en low
1ms
$03 write4Bits
5 ms
$03 write4Bits
5 ms
$03 write4Bits
1ms
$02 write4Bits \ Select 4 bit interface
2 ms
$28 writeCommand \ Set to 2 line mode
2 ms
$08 writeCommand \ Display off
2 ms
$01 writeCommand \ Clear display
10 ms
$06 writeCommand
\ Setup content of display control
$08 displayControl !
\ Turn backlight on
bl high
;
\ Type RAM based string at char position
: typeString ( addr count --- )
0
do
dup
i + c@ writeData
loop
drop
;
\ Type FLASH based string at char position
\ FLASH cells usually contain 2 characters
variable addr
variable count
variable count2
variable flag
: iTypeString ( addr count --- )
count ! addr !
count @ 1 rshift count2 !
count @ 2 mod 0 <> flag !
count2 @
dup ( --- count2 count2 )
0 <> ( count2 count2 --- count2 f )
if ( count2 f --- count2 )
0
do
addr @ @i dup
$FF and writeData
8 rshift writeData
1 addr +!
loop
else
drop
then
flag @
if
addr @ @i $FF and writeData
then
;
\ Perform setup and display test message
: test
initLCD \ Initialize the LCD
true displayMode \ Turn display on
5 1 setCharPosition \ Set position of next character write
s" Hello World" \ String compiled into FLASH
iTypeString \ Type the FLASH string
;
Enjoy
Craig Lindley
If you’re one in a million, there are now seven thousand people exactly
like you.
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