I'm trying to write a simple delay function. It takes two arguments: a pointer to a void function and an unsigned integer (unsigned int) specifying how many times the function should be executed. However, I'm encountering a dead loop, preventing the code after the function call from executing.
void delay(void (*func)(void), unsigned int time) {
unsigned int i, j;
for (i = 0; i < time; i++) {
func();
for (j = 0; j < 10000; j++);
}
}
In an attempt to avoid using functions, I implemented the following code:
void main() {
unsigned int i, j;
for (i = 0; i < time; i++) {
for (j = 0; j < 10000; j++);
func();
}
// other codes to be executed
}
I was surprised to find that this code avoids the dead loop I encountered previously. I'm confused about this. Maybe it has something to do with the function pointer? (The complier is Keil C51)
Keil supports the __nop() function that does nothing but isn't optimized out by the compiler. So you might write a delay function like this:
void delay(unsigned int time)
{
while(time--)
{
__nop();
}
}
If for some reason your compiler doesn't have __nop(), you can also do the following to generate a proper NOP in Keil C51.
#pragma asm
NOP
#pragma endasm
Of course it would be better to use a hardware timer to get a precise delay. But if you just want "some" dealy the above should be fine.