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brood
Joined: 23 Jan 2007
Posts: 12
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| Passing data using pointers on a pic16f917 |
 Posted: Sun Jan 28, 2007 7:41 am |
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Hi
I'm working on a mechanically scanned display. my problem is that when i look through the string and point to the constant array the out put i get is wrong. my display function was tested separate and it works, i would believe my error is in my character processing function.
Could some one please help, my code can be seen below.
| Code: |
#include <16F917.H>
#include <CTYPE.H>
#fuses INTRC_IO,NOPROTECT,NOWDT,PUT
#use delay(clock=8000000)
#use standard_io(a)
#use standard_io(b)
#use standard_io(c)
#use standard_io(d)
#case
//**************************************************************************************************
// Global variables
//**************************************************************************************************
int length;
int colour;
int16 stringptr;
//**************************************************************************************************
//16X10 font map
//**************************************************************************************************
const unsigned int16 A[10] = {0xFFF8, 0xFFFC, 0x0186, 0x0183, 0x0181, 0x0181, 0x0183, 0x0186, 0xFFFC, 0xFFF8}; //A
const unsigned int16 B[10] = {0xFFFF, 0xFFFF, 0xC183, 0xC183, 0xC183, 0xC183, 0xC183, 0xE3C7, 0x7FFE, 0x3E78}; //B
…
…
…
const unsigned int16 Z[10] = {0xF003, 0xF803, 0xCC03, 0xC603, 0xC383, 0xC1C3, 0xC063, 0xC033, 0xC01F, 0xC00F}; //Z
const unsigned int16 Number[10][10] =
{
{0x3FFC, 0x7FFE, 0xC00F, 0xC03B, 0xC1E3, 0xC783, 0xDC03, 0xF003, 0x7FFE, 0x3FFC} //0
…
…
…
{0x307C, 0x60FE, 0xC1C7, 0xC183, 0xC183, 0xC183, 0xC183, 0xE3C7, 0x7FFE, 0x3FFC} //9
}; // number array
//**************************************************************************************************
// Message
//**************************************************************************************************
const int16 msg1[] ={"AB 12"};
//**************************************************************************************************
// Output function
//**************************************************************************************************
void display(int top, int bottom)
{
switch (colour) {
case 1: // outputs red
output_a(top); // display on the topline in red
output_b(bottom); // display on bottomline in red
delay_ms(2000);
break;
case 2: // outputs green
output_c(top); // display on the topline in green
output_d(bottom); // displays on bottomline in green
delay_ms(2000);
break;
case 3: // outputs yellow
output_a(top); // display on the topline in red
output_b(bottom); // display on bottomline in red
output_c(top); // display on the topline in green
output_d(bottom); // displays on bottomline in green
delay_ms(2000);
break;
default:
colour = 1;
break;
}
}
//**************************************************************************************************
// Character check
//**************************************************************************************************
void Char_prosessing(int16 *charptr)
{
length = 0;
if (isalpha(charptr))
{
if (length <= 10)
{
display(make8(charptr[length],0), make8(charptr[length],1)); // splits the 16bit value into 2 8bit values and displays
length++;
} // end if
else
{
display(0x00, 0x00);
}
}
else if (isdigit(charptr))
{
if (length <= 10)
{
display(make8(Number[charptr][length],0),make8(Number[charptr][length],1));
length++;
} // end if
else
{
display(0x00, 0x00);
}
}
else if (isspace(charptr))
{
if (length <= 10)
{
display(0x00, 0x00);
length++;
} // end if
}
}
//**************************************************************************************************
// Main Program
//**************************************************************************************************
void main()
{
setup_lcd(LCD_DISABLED); // disables lcd display to access digital outputs
length = 0;
colour = 1;
stringptr = 0;
for (;;)
{
if (msg1[stringptr] != '\0')
{
Char_prosessing(msg1[stringptr]);
stringptr++;
} // end if
else
{
stringptr = 0;
if (colour <= 3)
{
colour++;
} //end if
else
{
colour = 1;
} //end else
} //end else
}
}
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Compiler version : 3.228
Thanks |
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Ttelmah
Guest
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| Posted: Sun Jan 28, 2007 10:09 am |
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RTFM......
CCS, doeas not support pointers to constants. ou can either declare the data in RAM (get rid of the const keyword), or you have to access the array directly, not using pointers.
Best Wishes |
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brood
Joined: 23 Jan 2007
Posts: 12
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| Posted: Tue Jan 30, 2007 5:27 am |
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Is there another way of doing the above without creating huge arrays in the ram? Because the PIC16F917 doesn't have enough ram to accomplish that.
Thank you in advance |
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Ttelmah
Guest
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| Posted: Tue Jan 30, 2007 5:35 am |
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Declare the array usng #ROM (which will directly store the sequence of bytes in memory), at a 'known' location (fixed by you), and then access it using the 'read_program_memory' function. The 16F914, is one of the few '16' chips, that supports doing this.
Best Wishes |
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