How to declare a matrix that is stored in PROGMEM

Question

I am trying to write a header file that will drive a LED Matrix but I'm stuck with a syntax error which I cannot resolve

I've already added " ; " everywhere I thought it was necessary and checked https://www.nongnu.org/avr-libc/user-manual/pgmspace.html

#ifndef max7219_H_
#define max7219_H_

#include <io.h>
#include <pgmspace.h>
#include <delay.h>
#include <stdint.h>

#define SLAVE_SELECT PORTB &= ~( 1<<PB4 );     
#define SLAVE_DESELECT PORTB |= ~( 1<<PB4 ); 

char characters[96][5] PROGMEM = 
{ 
   {
    0b00000000,
    0b00000000,
    0b00000000,
    0b00000000,
    0b00000000 
    }  
};

ERROR IS : Error: max7219.h(15), #included from: p2.c: ';' expected

line 15 is char characters[96][5] PROGMEM = ...

`char characters[96][5] PROGMEM` is invalid. Why add `PROGMEM`? — Paul Ogilvie, Apr 20 '19 at 15:26
BTW the previous macros perhaps shouldn't have the trailing `;`, otherwise it is easy to make mistakes with `if` without braces... — Antti Haapala -- Слава Україні, Apr 20 '19 at 16:01
when I was finishing using AVRs I started to use named address spaces instead of progmem. You should search for `__flash` `__memx` etc etc — 0___________, Apr 20 '19 at 16:02
If the array is made const, [I don't see any compile errors](https://godbolt.org/z/urGqjS). Are you sure this is your actual source file? Are you sure you don't have any other warnings, e.g. "unable to find `pgmspace.h`" or something? Perhaps you meant `avr/pgmspace.h`? If `PROGMEM` is not defined, then you would get a [similar error](https://godbolt.org/z/Uyi_Y9). — vgru, Apr 20 '19 at 17:54
@Groo .. yes that was a cpoy - paste from the source code , and no for some reason CodeVision has no ideea what is but it knows it as ... At the end I had succeded (?) in resolving the error i had to declare it as `code` PROGMEM char characters[96][5] `/code` — Spam97, Apr 21 '19 at 18:18

score 0 · Answer 1 · answered Apr 20 '19 at 17:37

0

You need to declare it const to put in flash. Also i am guessing that you need to make two arrays.

Try:

     const char c1[] PROGMEM = "1";
     const char c2[] PROGMEM = "2";

     const char * const strings[] PROGMEM = {c1, c2};

answered Apr 20 '19 at 17:37

Vilhelm

717
1
7
12

That one did not work either , I think there something particular to the CodeVison AVR ... After some more fiddling I got rid of the error , the answer was to move PROGMEM at the start of the delaration like this : PROGMEM char characters[96][5] – Spam97 Apr 21 '19 at 18:09

score 0 · Accepted Answer · answered Apr 24 '19 at 07:59

const PROGMEM uint8_t characters[96][5] = {
    {
      0b00000000,
      0b00000000,
      0b00000000,
      0b00000000,
      0b00000000 
   },
    ... // 95 more symbols
 };

Note, if an array declared with dimension, it should contain all the data in the initializer, i.e. all 96 symbols.

UPD: The error could be caused by the code in pc2.c just before #include "max7219.h" If you have several "includes", then check the previous one. I.e:

#include "a.h"
#include "b.h"
#include "max7219.h"

the error may be at the end of b.h

How to declare a matrix that is stored in PROGMEM

2 Answers2