Thread: get “error :lvalue required as left operand of assignment ” when set value for regist

I can not solve this problem. I don't understand why. Here is my simple code

Code:

mjpeg.h:

    #define START_REG                 (*(volatile unsigned int*) BASE+0x000)  
    #define MJPEG_PIC_START_RD                                  (0x00000001)

Code:

mjpeg.c:
    void encStreamInit(void){
    START_REG |= MJPEG_PIC_START_RD;
    }

Code:

test.c:
    int main(void){
     encStreamInit();
     return 0;
    }

It get "error: lvalue required as left operand of assignment" when compiling. Please help me. Thank for your help.

From what I can see it looks as if an lvalue is required as the left operand of your assignment .

START_REG is a macro definition, not a variable. You cannot assign to a macro as it is literally replaced with the expression that you define it as before compilation begins. If BASE is a variable (hopefully it's not because upper case variable names aren't particularly good practice) then it is still wrong because you're dereferencing a variable and then adding something to it which makes it an expression. You can't assign to expressions.

I'm guessing BASE is probably a defined address and maybe this is like embedded programming or something. I'm fairly sure the same reasoning as above applies. Remember that dereference operator has higher precedence than addition.

"*(volatile unsigned int*) BASE+0x000" is not a thing that can be assigned to, since it is an expression. Did you mean to cast "BASE+0x000" to a pointer, then dereference it? If so, your parentheses start in the wrong place for that -- as it is now, BASE is being dereferenced, and then 0x000 is being added to that dereferenced value.

Thank you all, I solved the problem.