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| Writing String and Character to an LCD |
 Posted: Thu Oct 20, 2005 8:34 am |
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How come when I use the following functions, lcd_putch and lcd_write, with strings it works? I understand why it works with just one character but how does it work when I send a string?
When I send
lcd_putch('c');
the lcd displays c
When I send
lcd_putch("string");
the lcd displays string.
Why does this work??? Shouldn't I have to write each letter of the string separately?
for instance...
lcd_putch('s');
lcd_putch('t');
lcd_putch('r');
lcd_putch('i');
lcd_putch('n');
lcd_putch('g');
then the LCD displays string
Here are the two functions I'm using...
| Code: |
void lcd_write(unsigned char c) {
//high order bit first
output_high(LCD_EN); //set enable high
output_bit(LCD_D7,c & 0x80); //put each bit on separate line
output_bit(LCD_D6,c & 0x40);
output_bit(LCD_D5,c & 0x20);
output_bit(LCD_D4,c & 0x10);
output_low(LCD_EN); //set enable low
//now low order bit
output_high(LCD_EN); //set enable high
output_bit(LCD_D7,c & 0x08); //put each bit on separate line
output_bit(LCD_D6,c & 0x04);
output_bit(LCD_D5,c & 0x02);
output_bit(LCD_D4,c & 0x01);
output_low(LCD_EN); //set enable low
delay_us(40);
}
void lcd_putch(unsigned char c) {
output_high(LCD_RS);
lcd_write(c);
}
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Everything works, I just want to understand why it works.
Thanks |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Oct 20, 2005 8:53 am |
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Read this on page 89 (in Acrobat reader) of the CCS manual:
| Quote: |
A (non-standard) feature has been added to the compiler to help get
around the problems created by the fact that pointers cannot be created
to constant strings.
A function that has one CHAR parameter will accept a constant string
where it is called. The compiler will generate a loop that will call the
function once for each character in the string.
Example:
void lcd_putc(char c ) {
...
}
lcd_putc ("Hi There."); |
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