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kel
Joined: 17 Oct 2005
Posts: 68
Location: Brisbane
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| LCD scrolling a Message!! |
 Posted: Sat Mar 25, 2006 10:34 pm |
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the following function give an error when called from main().The error measage is"ATTEMPT TO CREATE CONST TO POINTER SPRINTF".
All I want is a function to scroll a measage. This function is modified from the a function presented in the PICCLITE I googled recently.
| Code: | void scroll_Msg(unsigned char rowz, char Msg[]){
char Tmp_Msg[21];
unsigned in k,flag,Msg_Head;
flag=Msg_Head=0;
if(rowz>1) rowz=1;
rowz*=40;
while(flag==0){
for(k=0; k<20; k++){
Tmp_Msg[k]=Msg[Msg_Head+k];
if(Msg[Msg_Head+k+1]==0)
flag=1;
}
Msg_Head++;
lcd_goto_xy(rowz,1); //go to line 1 first row
lcd_putc(Tmp_Msg);
delay_ms(100); //delay 100 ms
}
}
void main(void)
{
//All initiallisations done here
while(1){
scroll_Msg(0,"A final year project!");
}
} |
this function compiled without error.However when I called from the main() as shown above, there is an error. | Code: | | ATTEMPT TO CREATE CONST TO POINTER SPRINTF |
My version is 3.24;
why is the compiler giving this error.Is there a problem with my compiler?
Can anyone help me out here!  |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Mar 25, 2006 11:21 pm |
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Kel,
If you read the forum regularly, you would have seen some of the
many, many posts on this topic. Here is one of them:
http://www.ccsinfo.com/forum/viewtopic.php?t=21588
If you want to do side-scrolling with an LCD, here is a demo program:
This one works with a 16x2 LCD.
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
// Put your LCD driver here.
#include <lcd.c>
void lcd_scroll_right(void)
{
lcd_send_byte(0, 0x1E);
}
//-------------------------
void lcd_scroll_left(void)
{
lcd_send_byte(0, 0x18);
}
//=======================
void main()
{
int8 i;
lcd_init();
lcd_putc("\f"); // Clear the LCD
delay_ms(100);
// The LCD memory is 40 characters wide, so fill it
// up with data for two screens. Each line below must
// contain 40 characters (excluding the newline).
lcd_putc("Hello to the Side scrolling \n");
lcd_putc("world. demo. ");
while(1)
{
for(i = 0; i < 20; i++) // Scroll for 20 chars
{
lcd_scroll_left();
delay_ms(350); // This sets the scroll speed
}
delay_ms(2000); // Wait 2 seconds between scrolling
// each screen.
}
} |
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kel
Joined: 17 Oct 2005
Posts: 68
Location: Brisbane
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| Thanks PCM Programmer! |
| Posted: Sun Mar 26, 2006 3:03 am |
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I believe you are highly qualified and respected member of this forum.Thanks you and those who have attempted.
Y couldn't my code work? |
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Ttelmah
Guest
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| Posted: Sun Mar 26, 2006 3:17 am |
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It is important to understand that the actual 'architecture' of a PIC, is not like most other processors. The PIC, has seperate 'code', and 'data' memories, with different addressing needed for each. Now, if you declare:
| Code: |
scroll_Msg(0,"A final year project!");
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The message "A final year project!", is generated and stored in _code_ memory, as a constant string. Now CCS, only supports 'pointers' to the _data_ memory. The thread that PCM Programmer points you to, explains this, and some of the approaches used to get round this.
In your case, if you declared:
| Code: |
char message[] = "A final year project!";
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Then the compiler would take the code declarations, and _automatically copy them into data memory_, to generate a character array, which can then be used in your function.
Similarly, you could do this yourself, by declaring a data array, and copying the array with 'strcpy', which is capable of moving arrays from the code memory to the data memory.
Best Wishes |
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kel
Joined: 17 Oct 2005
Posts: 68
Location: Brisbane
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| Guess this should work now!! |
| Posted: Sun Mar 26, 2006 9:13 pm |
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I guess this should work now.I haven't tried it yet.
| Code: | void scroll_Msg(unsigned char rowz, char Msg[]){
char Tmp_Msg[21];
unsigned in k,flag,Msg_Head;
flag=Msg_Head=0;
if(rowz>1) rowz=1;
rowz*=40;
while(flag==0){
for(k=0; k<20; k++){
Tmp_Msg[k]=Msg[Msg_Head+k];
if(Msg[Msg_Head+k+1]==0)
flag=1;
}
Msg_Head++;
lcd_goto_xy(rowz,1); //go to line 1 first row
lcd_putc(Tmp_Msg);
delay_ms(100); //delay 100 ms
}
}
void main(void)
{
//All initiallisations done here
char message[] = "A final year project!";
while(1){
scroll_Msg(0,message);
}
} |
Will the compiler still complain? |
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