limiting variables to a step size

[brownt]

there is a variable that can change from 0 - 100. And I would like the step size to be variable.
e.g. 0, 1, 2, 3.....
2, 4, 6 ....
10, 20, 30, ...... etc

aside from a huge if else statement like this

if (value < stepSize)value = 0;
else if(value < stepSize * 2) value = stepSize * 1;
else if(value < stepSize * 3) value = stepSize * 2;

what can I do?

I thought it would be easy to do, but I have spent all day without success.

thanks

[john.c]

I don't understand the problem. Why can't you just do this:

for (int i = 0; i <= 100; i += step_size)
    ...

[brownt]

thanks. Cannot afford the delay of a for loop, it is an interrupt routine. On a single pass through the function, it must be determined that the value has increased or decreased by the step size, and then the lower boundary needs to be displayed. So, for example if the step size is 10, then any values from 0 -9 will show as 0, 10 - 19 will show as 10, etc.

[Salem]

Not being able to afford a for loop sounds like premature optimisation disease to me.

> So, for example if the step size is 10, then any values from 0 -9 will show as 0, 10 - 19 will show as 10, etc.
Perhaps
result = (value / step_size ) * step_size;

[brownt]

Not being able to afford a for loop sounds like premature optimisation disease to me.

> So, for example if the step size is 10, then any values from 0 -9 will show as 0, 10 - 19 will show as 10, etc.
Perhaps
result = (value / step_size ) * step_size;

WOW, that's impressive, to me anyway. So simple. I have been banging my head on the desk all day, and had just finished writing out 64 if else statements to do the job, which works, but is so poor in design. That's great thanks.

Now I need to work out how to wind it up to 127 from the last step. For example, if the step size is 32, then it won't go any further than 96. Any clues for me?

Actually, I have it, but i guess there would be more elegant ways.

int temp = value;
result = (value / step_size ) * step_size;
if(temp == 127) value = 127;

[brownt]

what have I done here. This was an earlier attempt, it worked but it was like some sort of filter that let the value slowly wind its way up to the highest step.
I actually like that delay for another feature, if I can make that delay variable. Can you tell me why this code winds up slowly to the highest step. About 1.5 seconds with a 10mS sample time.

      if(value >  prevValue + stepSize) {prevValue += stepSize; } 
        else if(value <= prevValue- stepSize) {prevValue -=stepSize; }
        value = prevValue;