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Help Please! Expression must evaluate to a constant (Solved)

 
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NWilson



Joined: 30 Jun 2011
Posts: 21
Location: King's Lynn. England

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Help Please! Expression must evaluate to a constant (Solved)
PostPosted: Thu Nov 16, 2023 8:37 am     Reply with quote

PCWHD Version 5.116

Hi all,

I’m trying to produce a hardware clone of an old instrument based on a siemens SAB-C165 microprocessor and port the code over to a PIC24FJ128GC006.
The instrument has dozens of menus with lots of messages and associated actions. TBH, being a hardware engineer, I am struggling to get the menu system ported over.

Can anyone help me out with the following error?

*** Error 27 "C:\Development\Hardware Clone\main.c" Line 69(4,5): Expression must evaluate to a constant

Here is a simplified snippet of code that shows the problem.

Code:
//****************************************************
// main.c
// Rev         : 1.0
// Start Date  : 16th November 2023
// Author      : Neil Wilson
//*********************************************************

#EXPORT (FILE=Menu_Test.hex)
#include <24FJ128GC006.h>
#device  ANSI
#device  ADC=12
#device  ICD=TRUE
#device  ICSP=1
#use delay(internal=32000000)

#FUSES   NOWDT                    //No Watch Dog Timer
#FUSES   CKSFSM                   //Clock Switching is enabled, fail Safe clock monitor is enabled

#define  MENU_INTRO 0
#define  MENU_MAIN  1
#define  MENU_FILE  2
#define  MENU_SYS   3  //Lots of menus ........
#define  BLANK      0
#define  MESS_ACC1  1
#define  MESS_ADC1  2
#define  MESS_ADC2  3
#define  MESS_CLE1  4
#define  MESS_CHE2  5
#define  MESS_BATLOW  6   // Lots of messages......

// a snippet of dictionary entries - lots of them!                                       
const char *message [] =   
{
   "                      ",     // 0 BLANK
   "Acceptable Range",           // 1 MESS_ACC1
   "ADC Setup",                  // 2 MESS_ADC1
   "ADC Test",                   // 3 MESS_ADC2
   "Clearing Memory ....",       // 4 MESS_CLE1
   "Check PSU",                  // 5 MESS_CHE2
   "** Battery Low ! ** "        // 6 MESS_BATLOW
};

struct zMenu
{
   int cText[8];                 // dictionary index for each display line
   unsigned char cAction[8];     // action code for each display line
   unsigned char cCsr;           // initial line for cursor to start from
   unsigned char cEscape;        // action on escape key
   unsigned char cTitle;         // title inverted flag
   void (*func)(void);           // function associated with this menu
};

const struct zMenu   sMenu0  =   // Menu 0 MENU_INTRO

   MESS_CLE1, 
   MESS_CHE2, 
   MESS_BATLOW
};                         

const struct zMenu   sMenu1  =   // Menu 1 = MENU_MAIN

   MESS_ACC1, 
   MESS_ADC1, 
   MESS_ADC2
};

const struct zMenu   *g_sMenu [] =   
{   
   {&sMenu0},  {&sMenu1} 
};

void showMenu (unsigned char cPage)
{
   unsigned char cLine;
   int8 cIndex;
   char chText[5], chBuff[25];
   
   cLine  = 0;                               // reset line pointer
   cIndex = g_sMenu[cPage]->cText[cLine];    // find dictionary entry
   strcpy(chBuff, message[cIndex]);          // format string on display line
   //display_string_xy(1, cLine, chBuff);    // display string on LCD             
   
   return;
}

void main()
{
   showMenu(MENU_MAIN);
   while(1)
   {;}
}


It's this bit, that it doesn't seem to like.

Code:
const struct zMenu   *g_sMenu [] =   
{   
   {&sMenu0},  {&sMenu1} 
};

Thanks in advance
Neil


Last edited by NWilson on Fri Nov 17, 2023 2:41 am; edited 2 times in total
Ttelmah



Joined: 11 Mar 2010
Posts: 19215

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PostPosted: Thu Nov 16, 2023 12:42 pm     Reply with quote

Start by getting rid of the const declarations.

You should find that things then work.
Then do a search here for why const is different in CCS from the ANSI
usage. It is fundamental and matters massively. There are ways partially
round this, but a lot of thought is needed, and the simplest will be to not
use const.
NWilson



Joined: 30 Jun 2011
Posts: 21
Location: King's Lynn. England

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PostPosted: Thu Nov 16, 2023 1:26 pm     Reply with quote

Thanks Ttelmah,
I'll try that tomorrow when I get to work.
NWilson



Joined: 30 Jun 2011
Posts: 21
Location: King's Lynn. England

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PostPosted: Thu Nov 16, 2023 1:34 pm     Reply with quote

I've just removed all the const declarations from the above code and it still gives me the same error.
I'm open to suggestions if anyone can help.
Best wishes
Neil
Ttelmah



Joined: 11 Mar 2010
Posts: 19215

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PostPosted: Fri Nov 17, 2023 2:32 am     Reply with quote

OK. The const part was going to give you problems later.

struct zMenu *g_sMenu [2] = {&sMenu0,&sMenu1};
NWilson



Joined: 30 Jun 2011
Posts: 21
Location: King's Lynn. England

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PostPosted: Fri Nov 17, 2023 2:39 am     Reply with quote

Brilliant! Thanks Ttelmah
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