Issue with Interfacing LCD with PIC16F877A

rjenkinsgb said:

You are writing an "E" to the display once a second?

If you mean it's not starting where you expect, you need whatever command the display uses to set the cursor (or write) position before sending data.

Note that often the text lines are not stored in contiguous display RAM, and you need to set the correct write position at each line change.

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Ian Rogers said:

Your LCD init needs to be in order.. Proteus expects the exact init routine.

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Ian Rogers said:

When I say exact.. The LCD should automatically run in 8bit but proteus needs to see it for simulation
1 must always be function set with lines set to 0 or 1, then cursor... display on/off etc..

Are you scrolling the text? as that model only shows 16 digits in a row.

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Ian Rogers said:

char a~z is 26 characters, BUT a string needs a terminator so use "char a[27] "
Also I see you are using CCS.. Its not good practice to declare variables in line.. That is a C++ trait and if you use any other compiler it will complain.. I'm surprized that CCS is letting that happen.

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Ian Rogers said:

Okay looking at the arduino example they are printing the full string to the DD ram.
You need to write the whole string to the screen, only then can you send the autoscroll command.

If you write the character one by one AND autoscroll at the same time the result will no be what you want.

write a string to screen function. and write the data first

Code:

void LCDstring(char * str)
   {
    while(*str !=0)
         LCDdata(*str++);
   }

Then scroll in a loop

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Farhaad said:

So to reconfirm. You're telling me that if I want to display a-z and scroll then like print 'a' on 0x8F(First Row Last Column) then move it to the left one column, then print 'b' on 0x8F and move it left one column, its not possible?

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Ian Rogers said:

I just made one using your hardware ( my labels are different )

Code:

char txt[] = {"hello world from the other side of mars"};
..
void LCDstring(char * str)
    {
    while(*str !=0)
        LCDdata(*str++);   
    }
..
..
void main(void)
    {
    LCDinit();
    LCDstring(txt);
    while (1)
        {
        LCDcmd(0x18);
        delayMs(300);
        }
 }

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Nigel Goodwin said:

The basic structure of an Hitachi based LCD module is usually 2 rows of 40 characters - the actual visible part (such as 2x16) is a 'window' on to that 2x40 memory space - if you hardware scroll the display it simply moves that 'window' left or right along the buffer.

I would suggest you do a loop to print the entire character set from 32 (space) to 128 one character at a time after each other, where you will see the action of the memory buffer, by which character appears as the first character of the second row.

Four line displays though come in a number of different configurations, so you need to know exactly which type you have, often they use two separate display chips, the first does the odd number lines, and the second does the even lines.

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Farhaad said:

Thank you will try it out. Meanwhile, I feel Im still not very clear with LCD operation. I know the commands and etc but during execution I'm a bit unsure how its gonna execute. Can you recommend anything to get more info on LCDs. And what kind of programs if I make would help me grasp the full concepts on LCD.


Edit: So the program which you mentioned its starts to print Characters(32[Space]-47[Backward Slash]) then on the second Row it starts from Character 96.
96-47 gives 49 Characters.
So the 16 Characters + 49 Characters are in the first row? How does it exceed 40?

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