C what is wrong with function?

Question

Hi i have problem with function to control my 4servos. I want to take this code to function but it's not working.

volatile float servo1;

            variable=  uart_getchar();
            _delay_ms(100);
            variable=variable/10;
            servo1=variable;
            sprintf(bufor,"Servo_1= %4.1f\n",servo1);
            uart_puts(bufor);

when this code is not in function everything is okay, servo works good. Problem is when i do this:

void get(float Servo, char Number)
{
            variable=  uart_getchar();
            _delay_ms(100);
            variable=variable/10;
            Servo=variable;
            sprintf(bufor,"Serwo_%c= %4.1f\n",Number,Servo);
            uart_puts(bufor);
}

and when i call get(servo1,'1');servo stayed in the same place all the time.. any idea what is wrong??

Do you know what `void f(int x) {x = 5;} int main() {int y = 7; f(y); printf("%i\n", y); return 0;}` prints? (in normal C, not AVR) — user253751, May 24 '16 at 21:23
@Mateusz It prints 7, because `x` is a different variable from `y`, and `x = 5;` changes `x`, not `y`. — user253751, May 24 '16 at 21:28
`void f(int* x) {*x = 5;} int main() {int y = 7; f(&y); printf("%i\n", y); return 0;}` — AdminXVII, May 24 '16 at 21:38
1) the variable: `variable`, is not declared. 2) if `variable` is not a float, then this line: `variable=variable/10;` will perform a integer divide, probably not what you want. — user3629249, May 25 '16 at 16:49

score 1 · Accepted Answer · answered May 24 '16 at 21:44

1

If you want to change a variable you passed to a function, you must use pointers.

Basically it's used like this:

void f(int* x){
  *x = 5;
}

int main() {
  int y = 7;
  f(&y);
  printf("%i\n", y);
  return 0;
}

In short, & get the address of the variable and * get the value at the address

answered May 24 '16 at 21:44

AdminXVII

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@Mateusz, if you like the answer, then 'select' it so this question will close AND `admin XVII` will be properly credited for the answer – user3629249 May 25 '16 at 16:53

C what is wrong with function?

1 Answers1