Const unsigned char ?

[bianchi77]

Guys,

I tried to use unsigned char below, but I got error, how can I fix it ?

const unsigned char data[] = {0xFF,0xF2,0x40,0xC0,0x19,0xB7,0x00,0x14,0x02,0xE6,0x5C,};
unsigned char *q;
q = data ;

..\Src\main.c(274): error:  #513: a value of type "const unsigned char *" cannot be assigned to an entity of type "unsigned char *"
                q = data;

Thank you

 

[KlausST]

Hi,

I may be wrong, but isn't char always unsigned, and it doesn't need the word "unsigned".

INT can be signed or unsigned.

Klaus

 

[pic.programmer]

Replace

const unsigned char data[] = {0xFF,0xF2,0x40,0xC0,0x19,0xB7,0x00,0x14,0x02,0xE6,0x5C,};

with

unsigned char data[] = {0xFF,0xF2,0x40,0xC0,0x19,0xB7,0x00,0x14,0x02,0xE6,0x5C};

In your array there is a comma in the end and that is the problem. Also you cannot create a const type array and assign the address to non const type pointer.

 

[Easyrider83]

Phisicaly, it could be possible because some microcontrollers using common address space for ram/flash/eeprom like stm8/32. So it is just a changing pointer to first address location. And it could work with type conversion like (const char *), but also will became unsave and can increase the risk on instability.

 

[FvM]

The problem can't be "fixed" without considering the memory model of your processor (which isn't mentioned at all) and how the specific compiler (must be known too) is implementing arrays of constant data.

I presume that the topic is somewhere discussed in the compiler user manual, did you review it at all? The compiler might provide a dedicated pointer type for constant data.

 

[Aussie Susan]

I think the compiler is having a problem with assigning a non-cont pointer to a const array. Given that declaration of the pointer, it implies that you can assign a new value to the pointed-to value which is not the case (as it might be stored in ROM as it is 'const').
Susan