I2C lcd ( arduino ) with PICBASIC, help

[iw2fvo]

Hi Steve,
no change using both codes.
I still have no backlight and no text.
I appreciate your assistance on this matter: thanks a lot.
I am not skilled enough to go deeper in those kind of codes ...
Regards,
Ambrogio

[pedja089]

Can I make one suggestion?
First connect few led on output of PCF8574, and control them. So you are sure that I2C communication woks.
Second connect LCD to PIC directly, get timing and control right.
Then just combine that two.

[EarlyBird2]

Try again

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 1000            ; 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:

I2CWRITE SDA,SCL, LCD_Addr, [%00000000] ' bck_lt= off
PAUSE 200
I2CWRITE SDA,SCL, LCD_Addr, [%00001000] ' bck_lt=on
PAUSE 200

LCD_Data = "T"
gosub LCD_Write: PAUSEUS 50
LCD_Data = "e" 
gosub LCD_Write: PAUSEUS 50
LCD_Data = "s" 
gosub LCD_Write: PAUSEUS 50 
LCD_Data = "t" 
gosub LCD_Write: PAUSEUS 50 
LCD_Data = "-" 
gosub LCD_Write: PAUSEUS 50 
pause 500
goto Main

[EarlyBird2]

The problem could be with the delay on power up not being long enough for the LCD to initialise before the PIC starts.

Adjust this line and test

;----[Initialize the LCD]-------------------------------------------------------
PAUSE 1000 ; LCD Power-on delay

and please let me know the result.

[iw2fvo]

Dear Steve:

Your suggested test gave me the response on the lack of operation. ( see the attached).
The pcf has P0, P5 and P6 not working. This is the reason of the trouble.
I will no longer buy components on Ebay expecially if chinese. That is very bad.
I have no words to express my state. I want to apologize .
Thanks for the help given to me since the beginning.
Will try to buy another expander board: do you know some reliable seller in Europe ?
Regards,
Ambrogio

[EarlyBird2]

Dear Steve:

Your suggested test gave me the response on the lack of operation. ( see the attached).
The pcf has P0, P5 and P6 not working. This is the reason of the trouble.
I will no longer buy components on Ebay expecially if chinese. That is very bad.
I have no words to express my state. I want to apologize .
Thanks for the help given to me since the beginning.
Will try to buy another expander board: do you know some reliable seller in Europe ?
Regards,
Ambrogio

No problem and no need to apologise. Could you do some more testing on this board?
Check the voltages on the P0 to P7 pins when this program is running.

DEFINE OSC 40 ' 10 MHz XTAL AND X 4 INTERNAL PLL 
DEFINE I2C_SLOW 1
C VAR portd.3 ' S_CLOCK 
D VAR portd.2 ' S_DATA
ADDR VAR BYTE 
ADDR = %01001110 ' dec 78 , hex 4E
CMD VAR BYTE
LCD_CMD VAR BYTE 
E VAR LCD_CMD.BIT2 
RS VAR LCD_CMD.BIT0
E=0:RS=0
LCD_CMD = 0
PAUSE 1000 

MAIN:

I2CWRITE D, C, ADDR, [%00000000] ' port off
PAUSE 200
I2CWRITE D, C, ADDR, [%11111111] ' port on
PAUSE 200

GOTO MAIN

If all pins change then the PCF8574 chip is good indicating that the fault is either bad soldering or bad PCB track. It is possible to solder jumper wire direct to pins for a temporary repair.