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Help on segmented LCD
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Sebastian20000



Joined: 09 Nov 2007
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Help on segmented LCD
PostPosted: Wed Nov 21, 2007 7:26 pm     Reply with quote

Hi,

I am using the CCS Compiler 4.042 and I am just rookie in programming.
I bought a test board from microchip.com which has an
lcd on board.

Now I just want to run this lcd. But I don´t know how to start.
Its a 39 segment display and my first idea is just to write a "hello world"
in this display.

Can anyone give me some hints how to start, or tell me some infomation links...


Sebastian
PCM programmer



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PostPosted: Wed Nov 21, 2007 7:31 pm     Reply with quote

Quote:
I bought a test board from microchip.com which
has an lcd on board.

Post the name of the Microchip board.
Sebastian20000



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PostPosted: Wed Nov 21, 2007 7:36 pm     Reply with quote

its called
PICDEM Mechatronics
Demonstration Board.
Sebastian20000



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PostPosted: Thu Nov 22, 2007 9:15 am     Reply with quote

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023837
rberek



Joined: 10 Jan 2005
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PostPosted: Thu Nov 22, 2007 11:12 am     Reply with quote

Why don't you look at the CD that comes with the board? It has all the user guides and several projects, including one that uses the LCD to make a digital clock (Project #4). It even has the MPLAB project with all the assembler code to make it go. If you're a beginner, that's a great place to start.

Even the link you provided has the PDF for the User Guide.
Sebastian20000



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PostPosted: Thu Nov 22, 2007 12:02 pm     Reply with quote

Hi,
yes I know the project 4. But the project data on the cd are
.asm assembler files.

I want to program with "C" and not in assembler, therefore I bought CCS-Compiler.
PCM programmer



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PostPosted: Thu Nov 22, 2007 5:43 pm     Reply with quote

I can look at the code later in the weekend, to see if it can easily be
translated to CCS LCD functions. Maybe on Sunday I can look at it.
Sebastian20000



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PostPosted: Sat Nov 24, 2007 7:53 pm     Reply with quote

@pcm programmer
That would be nice. thx
PCM programmer



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PostPosted: Mon Nov 26, 2007 1:53 am     Reply with quote

Here is a test program for the LCD on the PicDem Mechatronics
Demonstration Board.

I don't have the Mechatronics board, so I can't test this program.
But I believe it has a good chance to work. I looked at the ASM
source code for the Mechatronics board. I've tried to make the
program below be similar to that ASM code, in terms of setting up
the LCD and by using the internal oscillator at 8 MHz.

I'm using the CCS lcd_symbol() function to turn on the three digits
on the right side of the LCD. I followed the method shown in the
CCS example file, Ex_LCD92.c. At this time, I don't have any code
to turn on the left-most '1' digit, or the decimal points, or any of the
special segments such as the diode or "low battery" segments.


Code:
#include <16F917.H>
#fuses INTRC_IO, NOWDT, NOPROTECT, NOBROWNOUT, PUT
#use delay(clock=8000000)

// The LCD digits are numbered in the following way, 
// according to the Varitronix VIM-332-DP data sheet.
//            _    _    _
//        |  |_|  |_|  |_|
//        |  |_|  |_|  |_|
//                     
// Digit  4   3    2    1
//

// The CCS lcd_symbol() function will be used to display digits
// 1, 2, and 3. The following define statements tell the
// lcd_symbol() function which PIC pins are connected to the
// LCD segment pins.
// There is a table on page 58 of the PicDem Mechatronics
// Demonstration Board data sheet which lists the connections
// that are used to make these define statements.
//
// Digit segments  A        B        C        D        E        F        G        DP
//                 b7       b6       b5       b4       b3       b2       b1       b0
#define DIGIT3  COM0+3,  COM0+11, COM2+11, COM3+3 , COM2+3,  COM1+3,  COM1+11, COM3+2
#define DIGIT2  COM0+6,  COM0+21, COM2+21, COM3+6,  COM2+6,  COM1+6,  COM1+21, COM3+11
#define DIGIT1  COM0+22, COM0+23, COM2+23, COM3+22, COM2+22, COM1+22, COM1+23, COM3+21

// The following array tells the CCS lcd_symbol() function which
// segments to turn on, to display the numbers from 0 to 9.
//                            0    1    2    3    4    5    6    7    8    9
byte const Digit_Map[10] = {0xFC,0x60,0xDA,0xF2,0x66,0xB6,0xBE,0xE0,0xFE,0xE6};

#define BLANK 0  // For a blank digit, don't turn on any segments.

#byte LCDDATA6 = 0x116
#bit  seg_4bc = LCDDATA6.2   // Controls left-most digit ("1")

int8 lcd_pos; 

//-----------------------------------------------
void lcd_putc(char c)
{
int8 segments;

if(c == '\f')
  {
   lcd_pos = 0;
  }
else
  {
   if((c >= '0') && (c <= '9'))
      segments = Digit_Map[c - '0'];
   else
      segments = BLANK;

   switch(lcd_pos)
     {
      case 1:           // 1000's digit (left-most digit on lcd)
        if(c == '1')        // Is the top digit = 1 ?
           seg_4bc = 1;     // If so, display it
        else                // If it's not = 1, don't display it.
           seg_4bc = 0;   
        break;
   
      case 2: lcd_symbol(segments, DIGIT3); break; // 100's digit
      case 3: lcd_symbol(segments, DIGIT2); break; // 10's digit
      case 4: lcd_symbol(segments, DIGIT1); break; // 1's digit
     }
  }

lcd_pos++;
}

//===================================
void main()
{
int16 number;

setup_lcd(LCD_MUX14 | LCD_BIAS_PINS, 0);

number = 1234;

printf(lcd_putc,"\f%4lu",number);   // Always send 4 digits

while(1);


-------
Edit:
Updated the code so that it's the same as the code shown on page 2 of
this thread. The code above incorporates two bug fixes, and it adds the
ability to display the left-most digit.


Last edited by PCM programmer on Tue Sep 16, 2008 6:01 pm; edited 2 times in total
Sebastian20000



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PostPosted: Mon Nov 26, 2007 12:25 pm     Reply with quote

Hi,
I test the program today and it works!
Thanks a lot.

One further question:

I don´t understand the line: c - '0' in the array:

Code:
segments = Digit_Map[c - '0'];
PCM programmer



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PostPosted: Tue Nov 27, 2007 2:10 pm     Reply with quote

Quote:
I don´t understand the line: c - '0' in the array:

segments = Digit_Map[c - '0'];

The lcd_putc() function expects to receive an ASCII number from 0 to 9
as the input value. ASCII numbers '0' to '9' have hex values of 0x30
to 0x39.

The code needs to use the input value as an index into the Digit_Map
array. But to do this, it must subtract off the ASCII "bias" of 0x30.
In other words, input values of 0x30 to 0x39 need to be converted to
values of 0x00 to 0x09. Then you can use it as an index into an
array which has 10 elements in it.

You could write the code to subtract the ASCII bias as
Quote:
c - 0x30

but it's very common for programmers to write it as
Quote:
c - '0'

because it shows very clearly that you're working with ASCII characters,
and that the base value of your index is derived from the ASCII number '0'.
Guest








Help on LCD of Mechatronics Demo board
PostPosted: Fri Sep 12, 2008 9:32 am     Reply with quote

I just copy and paste the code above and when I compile. The following error encounter.

Quote:

Executing: "C:\CCS_PIC\PCM\PICC\Ccsc.exe" "lcd.c" +FM +DF +LN +T -A +M +Z +Y=9 +EA
*** Error 12 "C:\PICC Experiment\Mechantronic\lcd.c" Line 69(23,36): Undefined identifier LCD_BIAS_PINS
1 Errors, 0 Warnings.
PCM programmer



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PostPosted: Fri Sep 12, 2008 10:01 am     Reply with quote

That constant is defined in all the 16F91x header files:
Quote:

c:\program files\picc\devices\16f913.h
#define LCD_BIAS_PINS 0x10

c:\program files\picc\devices\16f914.h
#define LCD_BIAS_PINS 0x10

c:\program files\picc\devices\16f916.h
#define LCD_BIAS_PINS 0x10

c:\program files\picc\devices\16f917.h
#define LCD_BIAS_PINS 0x10

If you don't have that #define statement, you're probably not using a
16F91x PIC. Or maybe you have a very old compiler version.
Guest








PostPosted: Fri Sep 12, 2008 10:13 am     Reply with quote

How to put all 4 digits on to the LCD.

e.g.

I want to output ADC channel 0 to the LCD, the min result = 0, the max= 1023.

What should I add to the code to do that?

Also anyone know the actual manf. # of the LCD so I can look at the datasheet.

Thanks..
dyeatman



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Posts: 1790
Location: Norman, OK

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PostPosted: Fri Sep 12, 2008 10:17 am     Reply with quote

According to the postings above it is:

Varitronix VIM-332

Here are the data sheets.

http://www.varitronix.com/LCDsearch.php?u=&query1=&page=6
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