ideal way to restart nested loops in C? - c

Question

I am a newbie to microcontroller C programming and I am running into a few problems with using nested loops.
Following is a sample construct that I have in my C code. The problems are mentioned subsequently
// I am trying to ramp down the while loop
while (i>= stop_value)
{
step_value = default_value;
R32(a particular register, content_register);
if (content_register = a_set_value)
{
if( step_value <= step_max)
{
step_value = step_value +1;
i=start_value;
continue;
}
if(step_value =step_max)
{
// do something;
break;
}
}
WR32(a particular register, content_reset_register); // resetting the register
i=i-1;
}
Basically, I am trying to do the following:
ramp down a loop till it reaches the stop_value and also read a particular register while ramping down.
If the register has a defined value, then check if the step_value<= step_max. If step_value < step_max then reset the while loop by using continue statement, and setting i to initial start value. At this point of time, my step_value should be the latest value and not the default step value. I do understand that above code is not completely correct for step_value because I initialize step_value to default_value.( So, how do I modify the initial step_value = default_value statement so that first time when the loop executes, I have a default_value and subsequently the most recent step_value?)
But, if step_value equals my step_max then just do something and break subsequently( this part works!). Also, when I use the continue statement, I should reset the contents of the register.
So, I want to effectively reset the while loop with the latest step_value, contents of the register reset when my step_value is less than step_max? Thank you for your replies!

Answer 1

In this code:
if( step_value <= step_max)
{
step_value = step_value +1;
i=start_value;
continue;
}
if(step_value =step_max)
{
// do something;
break;
}
The second if cannot ever be reached. You are checking <= and then skipping to the bottom of the loop with continue.
From your above logic:
then check if the step_value<= step_max. If step_value < step_max then reset the while loop by using continue statement, and setting i to initial start value.
That code should probably read:
if( step_value < step_max)
{
step_value = step_value +1;
i=start_value;
continue;
}
...
Then the second if could be evaluated. This should be generating compiler warnings like crazy about unreachable code and assignment within if statements. Please turn on your compiler warnings and listen to them!

Answer 2

I assume that at least one of the following alternatives apply:
First, in C language = is an assigment which returns the value assigned and assumes true if that value is not equal to 0.
So you have to use == in all if statements instead of = (unless it is desired behaviour that you assign and check for != 0 in the if statement in one step - but even in that case I'd prefer to do this in 2 steps for better maintainability), i.e. instead of
if (content_register = a_set_value)
{
// your code
}
I would say
content_register = a_set_value;
if (content_register!=0)
{
// your code
}
to make it more clear what you're checking against.
Second, if step_value==step_max (and you're properly using == in the 2nd if) then both IFs are executed, which is not what you want. So you I assume you meant < instead of <=.
Third, from our chat I got the information from you that the loop is waiting for a register change coming from an external thread. In this case the loop is simply too fast resetting the register. Consider synchronization or at least add a thread sleep after resetting the register to allow the other thread to change the register.
Change this and see if it works.