Quote Originally Posted by iw2fvo View Post
Steve,
Thanks a lot for the intersest.
It does not work. I added the bck_lt flashing in the main loop just to see if the communication is good > the bck_lt comes ond goes correctly.
I am attaching the whole program
Ambrogio
Code:
'****************************************************************
'*  Name    : RKPK40 board pic18F452  40 MHz                    *
'*  Author  : [select VIEW...EDITOR OPTIONS]                    *
'*  Notice  : Copyright (c) 2014 [select VIEW...EDITOR OPTIONS] *
'*          : All Rights Reserved                               *
'*  Date    : 23/06/2014                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************

';Program Configuration Register 1H
@		__CONFIG    _CONFIG1H, _OSCS_OFF_1H & _HSPLL_OSC_1H      

';Program Configuration Register 2L
@		__CONFIG    _CONFIG2L, _BOR_OFF_2L & _BORV_20_2L & _PWRT_ON_2L

';Program Configuration Register 2H
@		__CONFIG    _CONFIG2H, _WDT_OFF_2H & _WDTPS_128_2H

';Program Configuration Register 3H
@		__CONFIG    _CONFIG3H, _CCP2MX_OFF_3H

';Program Configuration Register 4L
@		__CONFIG    _CONFIG4L, _STVR_OFF_4L & _LVP_OFF_4L & _DEBUG_OFF_4L

';Program Configuration Register 5L
@		__CONFIG    _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L 

';Program Configuration Register 5H
@		__CONFIG    _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H

';Program Configuration Register 6L
@		__CONFIG    _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L 

';Program Configuration Register 6H
@		__CONFIG    _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H

';Program Configuration Register 7L
@		__CONFIG    _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L & _EBTR2_OFF_7L & _EBTR3_OFF_7L

';Program Configuration Register 7H
@		__CONFIG    _CONFIG7H, _EBTRB_OFF_7H


DEFINE OSC 40 ' 10 MHz XTAL AND X 4 INTERNAL PLL 
DEFINE I2C_SLOW 1
SDA         VAR PORTD.2       ; I2C Data pin
SCL         VAR PORTD.3       ; I2C Clock Pin
LCD_Addr CON 78
'LCD_BuffSize    CON 30
'LCD_Buff        VAR BYTE[LCD_BuffSize]
'LCD_BuffAddr    CON EXT : @LCD_BuffAddr = _LCD_Buff
'LCD_BuffLen     VAR WORD        ; Length of data in buffer
LCD_Data        VAR BYTE        ; Data to Send to LCD
LCD_Byte        VAR BYTE        ; Nibbles to Send
LCD_RS          VAR LCD_Byte.0  ; Register Select bit
LCD_RW          VAR LCD_Byte.1  ; Read/Write bit
LCD_E           VAR LCD_Byte.2  ; Enable bit
LCD_BackLight   VAR LCD_Byte.3  ; Backlight 0=ON
LCD_WriteMode   VAR BYTE        ; 1=LowNibble, 2=HighNibble, 3=Both
LCD_CommandMode VAR BIT         ; Indicates next byte is a command
LCD_Byte2       VAR BYTE        ; Same nibble without E bit
LCD_Idx         VAR BYTE
testmode        var byte



;----[Initialize the LCD]-------------------------------------------------------
PAUSE 250             ; LCD Power-on delay
LCD_Backlight = 1     ; Backlight OFF
LCD_RW = 0            ; Write to LCD
LCD_RS = 0            ; Command Register

LCD_WriteMode = 1     ;-- Low Nibbles only
LCD_Data = 3          ; Reset 3 times
gosub LCD_Write_
PAUSEUS 6000
gosub LCD_Write_
PAUSEUS 1000
gosub LCD_Write_
PAUSEUS 1000

LCD_Data = 2          ; Start 4-bit mode
gosub LCD_Write_
PAUSEUS 1000

LCD_WriteMode = 3     ;-- Both Nibbles
LCD_Data = $28
gosub LCD_Write_      ; Function Set, 4-bit, 2-line, 5x7
LCD_Data = $0C
gosub LCD_Write_      ; Display ON
LCD_Data = $01
gosub LCD_Write_      ; Clear Screen
PAUSE 2
LCD_Data = $06 
gosub LCD_Write_      ; Entry Mode
                       
PAUSE 2               ; Let command finish
LCD_RS = 1   ' this is data
goto main

LCD_WRITE_:
   LCD_E = 1
   IF LCD_WriteMode.1 = 1 THEN                             ; Write High Nibble
     LCD_Byte = (LCD_Byte & $0F) | (LCD_Data  & $F0)
     LCD_Byte2 = LCD_Byte & $FB    
     I2CWRITE SDA,SCL, LCD_Addr,[LCD_Byte, LCD_Byte2]
   ENDIF
  
   IF LCD_WriteMode.0 = 1 THEN                             ; Write Low Nibble
     LCD_Byte = (LCD_Byte & $0F) | ((LCD_Data << 4 )& $F0)
     LCD_Byte2 = LCD_Byte & $FB
     I2CWRITE SDA,SCL, LCD_Addr,[LCD_Byte, LCD_Byte2]
   ENDIF
return



Main:
LCD_Data = "T"
gosub LCD_Write_ 
LCD_Data = "e" 
gosub LCD_Write_
LCD_Data = "s" 
gosub LCD_Write_ 
LCD_Data = "t" 
gosub LCD_Write_ 
goto main
I over simplified the program!
need to add this line

LCD_RS = 1 ' this is data highlighted in red above. This switches from command mode to data. It was in command mode that is why your back_lt instructions worked. An excellent clue for me.

I am not sure about these lines

LCD_Data = $28
gosub LCD_Write_ ; Function Set, 4-bit, 2-line, 5x7

and what the location addresses are to position the cursor at the beginning of each line.

Have you a datasheet for this LCD?

When this simple example is working we can add Command/Data switching which we will obviously need to have. I will follow Darrel's method as close as possible, he uses $FE to indicate the next byte is a command and switches to command mode for one byte then back to data.

Plenty for me to think about.