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interfacing PIC16f676 to CFAH8002A-YYH-JP

live2surf

New member
Initially I tagged my problem at the end of another thread but I would like more input so I decided to start a new thread.

My problem is this;

I have successfully interfaced my PIC16f676 to an Optrex DMC 50448N LCD using the built in LCD functions provided in PIC Basic Pro. I then found Crystalfontz's website and found their LCDs to be cheaper in volume then optrex so I decided to use them in my design. The problem is that when I got the Crystalfontz LCD CFAH0802-YYH-JP and dropped it into the circuit in place of the optrex it did not work. I thought that these type of LCDs, i.e. HD44780 or equivalent , were or should be interchangable. Is this not the case? Has anyone run into similiar issues and if so how were they resolved?

I am now trying to manually initialize the LCD and write data to it without using the builtin LCD functions. Here is my setup. I am using a 4-bit bus, the R/W line is hardwired low for write only, D7-D4 are wired to PORTC pins 3-0 respectively, enable is wired to PORTC bit 5, and RS bit is wired to PORTC bit 4. the PIC16f676 is a 14 pin chip and I have no spare I/O pins or any other pins for that matter available to change design it must work in this configuration or I will be forced back to Optrex LCDs.

I have spent several DAYS trying different combinations of the initalization sequence from the Cfontz datasheet to no avail. the closest I have come is to get the LCD initialized, I think!?, but cannot get characters to display. At the end of the initialization sequence I get either a cursor with a blinking square or a the last character before the square, a small o with two dots on top, in position one and then a cursor with a blinking square in position two. Then when I try to write data it looks like it wants to display but ll I get are squares appearing. Not only that but two at a time like it does not recognize that I am in 4-bit mode where it takes two writes to transfer the 8-bit character to the DDRAM. I am baffeled. Here is my code I am using to try this manual initialization and writing. I use very long pauses in there so I can see what the display looks like after each step. Any and all suggestions or comments are welcome. :D

TRISC = 0
'LCD INIT
PAUSE 2000

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100011 'FIRST TIME
PAUSEUS 1
PORTC.5 = 0

PAUSE 100

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100011 'SECOND TIME
PAUSEUS 1
PORTC.5 = 0

PAUSE 100

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100011 'THIRD TIME
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100010 'FUNCTION SET (SET INTERFACE TO 4 BITS LONG)
PAUSEUS 1
PORTC.5 = 0

PAUSE 5000

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100010 'FUNCTION SET (SET INTERFACE TO 4 BITS LONG)
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %101000 'FUNCTION SET DISPLAY LINES = 2 FONT = 5X8
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100000 'DISPLAY ON
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %101110
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100000 'DISPLAY CLEAR
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100001
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100000 'ENTRY MODE SET
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100110
PAUSEUS 1
PORTC.5 = 0

PAUSE 5000

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100000 'CLEAR DISPLAY
PAUSEUS 1
PORTC.5 = 0

PAUSE 1

PORTC.4 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %100001
PAUSEUS 1
PORTC.5 = 0

PAUSE 5000


'WRITE DATA TO DDRAM
MAIN:

PORTC.4 = 1
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %110011 'SEND UPPER NIBBLE
PAUSEUS 1
PORTC.5 = 0
PAUSEUS 1
PORTC.5 = 1
PAUSEUS 1
PORTC = %110011 'SEND LOWER NIBBLE
PAUSEUS 1
PORTC.5 = 0

PAUSE 5000

GOTO MAIN
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Yes, it seems that any HD44780 compatible display should behave the same. Your code looks correct, and I don't know why its not working. My only suggestion is to put the enable strobe after the data is output. I know the data sheet shows that this is not necessary, but I have always done it this way, and I've never had problems with character displays. Like this:
Code:
PORTC.4 = 0
PAUSEUS 1
PORTC = %000011 'FIRST TIME
PORTC.5 = 1
PAUSEUS 1
PORTC.5 = 0
Do you have a scope, such that you could look at the data vs. control signal timing, and verify what is happening?

Afterthought: try tying the display inputs D0~D3 low. Again, it shouldn't matter, but I've heard of it curing problems. Also, I think you don't need to do CLEAR DISPLAY twice, but no big deal.
 

CF Tech

Administrator
If you carefully port this:
Code:
/////////////////////////////////////////////////////////////////////////////
void CCFAH_WinTestDlg::Write_LCD_Control_8(ubyte data,ubyte enable)
  {
  //Make register select 0, Make R/W 0=write
  OnRsL();
  OnRwL();
  //Write the data to the port.
  data_register=data;	
  Update_Buttons_From_Data_Register();
  //Strobe enable
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  }
/////////////////////////////////////////////////////////////////////////////
void CCFAH_WinTestDlg::Write_LCD_Data_8(ubyte data,ubyte enable)
  {
  //Make register select 1, Make R/W 0=write
  OnRsH();
  OnRwL();
  //Write the data to the port.
  data_register=data;	
  Update_Buttons_From_Data_Register();
  //Strobe enable
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  }
/////////////////////////////////////////////////////////////////////////////
void CCFAH_WinTestDlg::Write_LCD_Control_4(ubyte data,ubyte enable)
  {
  //Make register select 0, Make R/W 0=write
  OnRsL();
  OnRwL();
  //Apply the high 4 bits of data to the high four bits of the port.
  data_register=data&0xF0;
  Update_Buttons_From_Data_Register();
  //Strobe enable to clock in the high nibble.
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  //Apply the low 4 bits of data to the high four bits of the port.
  data_register=(data<<4)&0xF0;
  Update_Buttons_From_Data_Register();
  //Strobe enable to clock in the low nibble.
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  }
/////////////////////////////////////////////////////////////////////////////
void CCFAH_WinTestDlg::Write_LCD_Data_4(ubyte data,ubyte enable)
  {
  //Make register select 1, Make R/W 0=write
  OnRsH();
  OnRwL();
  //Apply the high 4 bits of data to the high four bits of the port.
  data_register=data&0xF0;
  Update_Buttons_From_Data_Register();
  //Strobe enable to clock in the high nibble.
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  //Apply the low 4 bits of data to the high four bits of the port.
  data_register=(data<<4)&0xF0;
  Update_Buttons_From_Data_Register();
  //Strobe enable to clock in the low nibble.
  Sleep(1);
  if(enable)
    {
    OnE1H();
    Sleep(1);
    OnE1L();
    }
  else
    {
    OnE0H();
    Sleep(1);
    OnE0L();
    }
  }
/////////////////////////////////////////////////////////////////////////////
void CCFAH_WinTestDlg::Init_LCD_4(ubyte enable)
  {
  //It is not an error that the first writes are "8-bit", see the HD44780
  //data sheet.
  //This sequence is from the initialization on page 46 of the HD44780U
  //data sheet.
  Sleep(40);
  Write_LCD_Control_8(0x30,enable);
  //Yes, the data sheet says write it twice.
  Sleep(5);
  Write_LCD_Control_8(0x30,enable);
  //Yes, the data sheet says write it three times.
  Sleep(125);
  Write_LCD_Control_8(0x30,enable);
  //Yes, the data sheet says write it four times, but at least this one counts.
  //020h is Function set:
  //4 bit,
  //2 line
  //F = (5x8)
  Sleep(1);
  //This is last 8-bit write, which is an instruction to put the LCD into 4-bit mode.
  Write_LCD_Control_8(0x20,enable);
  //Here is the 4-bit instruction to set the font and number of lines.
  Write_LCD_Control_4(0x28,enable);
  //"Display off"
  Sleep(2);
  Write_LCD_Control_4(0x08,enable);
  //"Display clear"
  Sleep(2);
  Write_LCD_Control_4(0x01,enable);
  //006h is Entry mode set, increment, no shift
	Sleep(2);
  Write_LCD_Control_4(0x06,enable);
  //Display on, cursor on, blinking
	Sleep(2);
  Write_LCD_Control_4(0x0F,enable);
  //Clear the display again. This seems to fix a power-up problem
  //where the display shows "{{{{{" in a couple of places.
	Sleep(2);
  Write_LCD_Control_4(0x01,enable);
  }
/////////////////////////////////////////////////////////////////////////////
From "CFAH_WinTestDlg.cpp" in CFAH_WinTest, it should work for pretty much any display.
 
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