Four Line LCD - LCD_EBIT

[cc1984]

Anybody got ideas on how to define/control two LCD_EBIT lines and still use the LCDOUT function? I have a Newhaven display that has an enable pin for the top half (first 2 lines) and also another one for the bottom half (last 2 lines). I tried to make a subroutine to redefine LCD_EBIT, but redefinition during runtime is not allowed. I can use LCDOUT to write to the top or the bottom half, but I need to write to both.... Any ideas would be appreciated.

[DaveC3]

Here is how I made a 4x40 work

'****************************************************************
'*  Name    : USBladem4X40LCD                                    *
'*  Author  : Dave Cutliff                                      *
'*  Notice  : Copyright (c) 2005 Patent pending                 *
'*          : All Rights Reserved                               *
'*  Date    : 7/22/05                                           *
'*  Version : 1.0                                               *
'*  Notes   : PIC18F2455                                        *
'*          :  LCD 4X40 Dual driver                                                 *
'****************************************************************



Define  OSC     48
'**** LCD *******************************************************
'Set LCD Data port
DEFINE LCD_DREG PORTB
'Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 4
'Set LCD Register Select port
DEFINE LCD_RSREG PORTB
'Set LCD Register Select bit
DEFINE LCD_RSBIT 0
'Set LCD Enable port
DEFINE LCD_EREG PORTB
'Set LCD Enable bit
DEFINE LCD_EBIT 3
'LCD RW Register PORT
'DEFINE LCD_RWREG PORTB
'LCD read/write pin bit
'DEFINE LCD_RWBIT 5
'Set LCD bus size (4 or 8 bits)
DEFINE LCD_BITS 4
'Set number of lines on LCD
DEFINE LCD_LINES 4
'Set command delay time in us
DEFINE LCD_COMMANDUS 2000
'Set data delay time in us
DEFINE LCD_DATAUS 50

LCD1_Disable    var portb.2
LCD2_Disable    var portb.1
'*** Program variables *****************************************
buffer1    Var    Byte[8]
buffer2    Var    Byte[8]
cnt    Var    Byte


lcdcnt     var  byte
'lcdchr     var  byte
lcdlen     var  byte
lcdline var byte
lcd var byte
lcdfunction var byte

'x          var  byte
'y          var  byte
'j          var  byte
k          var  byte
'ln         var  byte
'tmp1       var  byte
'***************************************************************
    USBInit
pause 500
' Initialize LCD
input LCD1_Disable 
input LCD2_Disable 
LCDOut $fe,1   'clear lcd
pause 100
LCDOut $fe,2   'home
LCDOut $fe,$0c 'Curser off
LCDOut "              USB 4X40 LCD   "
LCDOut $FE,$C0
LCDOut "              DAVE CUTLIFF    "
low LCD1_Disable 
input LCD2_Disable 
LCDOut $fe,1   'clear lcd
LCDOut $fe,2   'home
LCDOut $fe,$0c 'Curser off
LCDOut "         Highspeed USB Project  "
LCDOut $FE,$C0
LCDOut "             August 2005    "   
pause 100
goto idleloop
'*********************subrouteens*************************
 READ_SETUP:
  USBService
  lcdlen = buffer1[3]
  lcdline = buffer1[1]
  lcdfunction = buffer1[2]
  lcd = buffer1[0]
    if lcd= 0 then
        input LCD1_Disable 
        LOW LCD2_Disable 
          else
        LOW LCD1_Disable 
        input LCD2_Disable 
    endif  
  if lcdfunction = 1 then lcdout $FE,1
  lcdout $FE,lcdline
  
 RETURN

 Write_LCD:
      USBService
      lcdcnt = 1
      While lcdcnt < lcdlen
          for k = 1 to 7
          lcdcnt = lcdcnt + 1
          LCDOUT buffer2[k]
          if lcdcnt = lcdlen then goto outloop
          usbin 2, buffer2, cnt, idleloop
          next k   
     
      wend
 Return


 outloop:
    USBService                                ' Must service USB regularly
    USBOut 1, buffer1, cnt, outloop            ' Send the bytes back
 return
'****************************************************************
' Wait for USB input of 8 numbers.
idleloop:
    USBService                                    ' Must service USB regularly
    cnt = 8                                        ' Specify input buffer size
    USBIn 1, buffer1, cnt, idleloop
    gosub READ_SETUP
    gosub outloop
    usbin 2, buffer2, cnt, idleloop
    GOSUB Write_LCD
    gosub outloop
    

goto idleloop

Hope this helps

Dave

[sayzer]

You may want to use a 7408;
This way, you can have one enable pin from PIC (coming from LCDOUT command), and two other Pins for each half.
When you want to write to first half, HIGH first and LOW second; and the other way around for second half.

[cc1984]

Great Ideas. Thanks!

[mister_e]

It's really up to you to decide which one to use, 7408 or not. Cost effective wise, I think Dave's approach is the one. Back in time
http://www.picbasic.co.uk/forum/showthread.php?t=626&

[cc1984]

So far what I have ended up with was 2 transistors, NPN and PNP (3904 & 3906). I tied one line from the pic to control the transistors, two 2.2K resistor going from the control line to the base of each transistor. I connected the LCDOUT control line to the collector of the NPN and the emitter of the PNP. I use the control line to turn on or off the control line to pass the enable signal to either the enable1 or enable2 on the lcd. I only had to add one IO line from the PIC and 2 transistors. I have 4 of these displays on the panel so I was not excited about adding more chips to the design. Not sure how to upload a schematic, but would like everyone/anyone to see if they see a problem with the design. However, it works great!
Thanks.