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const structs

 
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hawke
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const structs
PostPosted: Sun Apr 22, 2007 7:25 pm     Reply with quote

Hello,
I have a number of structures in program memory. What is the reccomended method to move these structures into RAM. I'm trying to create a flexible menu on a small LCD. I want only one menu function to operate on different sets of structures. The RAM is not available to store everything there. So I'm left with putting these various structure in program memory. The big question is how do I specify different program memory structures without having a separate menu function for each?
I seem to be in a catch-22. plenty of storage in program memory for constants, But how to use them dynamically.
Thanks
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Apr 23, 2007 12:03 am     Reply with quote

I'm not sure exactly what you're asking for. Maybe this will help.
Here is demo program which displays some LCD menu strings
that are stored in structures, in a 'const' array.

The program was run in the MPLAB simulator. The output was sent
to 'UART1' and displayed in the Output Window as shown below:
Code:

Menu 1
Menu 1, Line 2
  sub-Menu 1A
  1A Line 2
  sub-Menu 1B
  1B Line 2
Menu 2
Menu 2, Line 2
  sub-Menu 2A
  2A Line 2
  sub-Menu 2B
  2B Line 2
  sub-Menu 2C
  2C Line 2
Menu 3
Menu 3, Line 2
  sub-Menu 3A
  3A Line 2
  sub-Menu 3B
  3B Line 2
  sub-Menu 3C
  3C Line 2
  sub-Menu 3D
  3D Line 2
Menu 4
Menu 4, Line 2
  sub-Menu 4A
  4A Line 2
  sub-Menu 4B
  4B Line 2


Code:

#include <18F452.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

typedef struct
{
char menu_type;
char menu_function_index;
char line1[17];    // For a 16x2 LCD 
char line2[17];
}menu_t;


#define MAX_INDEX  15     

// The PCH compiler allows const arrays larger than 256
// ROM words, so it's much better than PCM for this purpose.
const menu_t menu_screens[MAX_INDEX] =
{
{0, 1, "Menu 1", "Menu 1, Line 2"},
    {1, 2, "  sub-Menu 1A", "  1A Line 2"},
    {2, 3, "  sub-Menu 1B", "  1B Line 2"},

{0, 1, "Menu 2", "Menu 2, Line 2"},
    {1, 2, "  sub-Menu 2A", "  2A Line 2"},
    {2, 3, "  sub-Menu 2B", "  2B Line 2"},
    {3, 4, "  sub-Menu 2C", "  2C Line 2"},

{0, 1, "Menu 3", "Menu 3, Line 2"},
    {1, 2, "  sub-Menu 3A", "  3A Line 2"},
    {2, 3, "  sub-Menu 3B", "  3B Line 2"},
    {3, 4, "  sub-Menu 3C", "  3C Line 2"},
    {4, 5, "  sub-Menu 3D", "  3D Line 2"},

{0, 1, "Menu 4", "Menu 4, Line 2"},
    {1, 2, "  sub-Menu 4A", "  4A Line 2"},
    {2, 3, "  sub-Menu 4B", "  4B Line 2"}
};   


void display_menu(int8 index);

//====================================
void main()
{
int8 i;


for(i = 0; i < MAX_INDEX; i++)
   {
    display_menu(i);
    printf("\r");
   }

while(1);
}     


//===============================
// FUNCTIONS
//-----------------------------------------------
void display_menu(int8 index)
{
printf("%s\r", menu_screens[index].line1);
printf("%s", menu_screens[index].line2);
}
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