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About LCD control

 
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jaethelegend
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About LCD control
PostPosted: Sat Jun 06, 2009 7:01 am     Reply with quote
Hi, I was originally using a full PORT with all 8 ports available to control a LCD display, connecting RA0~2 to RS,RW,EN and RA4~7 to D04~7.
It worked fine.

Now, i tried to practice different ways of doing it for later use by
connecting RA0~3 to D4~7 and RS to D5, RW to D6, R7 to EN.

I guess the biggest difference between first coding scheme and the second coding scheme is that in first coding scheme, i controlled(outputted) the entire 7 required bits to the LCD at a time. In second time, I played with the output ports before i pulsed enable signal.
below is quick code example
First Scheme which worked fine.
Code:
void Busy_Check(){
   int8 high_nibble, low_nibble;
   do{
      LCD_TRIS = 0b10000000;
      LCD_PORT = 0b00000110; // RS=0, RW=1 EN=1
     
      delay_us(14);
      high_nibble=LCD_PORT;
      delay_us(14);
     
      LCD_PORT = 0b00000010;       //RS = 0, RW = 1, EN = 0
      LCD_PORT = 0b00000110;       //RS = 0, RW = 1, EN = 1
     
      delay_us(14);
      low_nibble = LCD_PORT;
      delay_us(14);
     
      LCD_PORT = 0b00000010;          // RS = 0, RW = 1, EN = 0
      }while(high_nibble&0x80);     
     
      LCD_TRIS = 0x00;
      LCD_PORT = 0x00;
   }



Second scheme which didn't work


Code:

void busy_check(void){
   int8 high_nibble, low_nibble;
   do{
      LCD_TRIS = 0b10000000;
      LCD_PORT = 0b00000000; // RS=0, RW=1 EN=1
      R_W = 1;
     E_N = 1;
     
      delay_us(14);
      high_nibble=LCD_PORT; //LCD로 부터 나오는 상위 니블 리드.
      delay_us(14);
      E_N = 0;
      E_N = 1;
      delay_us(14);
      low_nibble = LCD_PORT;
      delay_us(14);
     
      E_N = 0;       // RS = 0, RW = 1, EN = 0
      }while(high_nibble&0x80);     //D7 이 1이면 받을 준비가 안됨.
     
      LCD_TRIS = 0x00;
      LCD_PORT = 0x00;
   }



Thank you, I appreciate your help
Steve H
Guest
PostPosted: Sat Jun 06, 2009 9:44 am     Reply with quote
You realize that in the 4 bit nibble mode - you have to go through a special initialize sequence for the LCD? You can find this in a bunch of places (try the CCS examples, Google or the LCD data sheet) or look at some of my code here,

http://geocities.com/hagtronics/wwvb.c

HTH - Steve H.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sat Jun 06, 2009 11:58 am     Reply with quote
See the Flex driver here:
http://www.ccsinfo.com/forum/viewtopic.php?t=24661

Also, the CCS LCD.c driver has flex capability starting with vs. 4.085.
jaethelegend
Guest
PostPosted: Sun Jun 07, 2009 9:46 pm     Reply with quote
Thanks guys!
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