how to use a volatile variable as a Boolean?

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hello,
I am doing imbedded programming in C and I was wondering how to use a volatile variable as a Boolean. In this case, I am reading some data and my variable is 'delta_X' which is a floating point. I would like
the unit to power down if this value does not change, say for 1 minute. How do I do this?

if (delta_X does not change for one minute)             {powerdown();}

I do not want to compare this value with a temp every time because it would be expensive.

Has anyone used an overflow counter to do a powerdown before?

Thanks in advance for you help.

2

I would like
the unit to power down if this value does not change, say for 1 minute. How do I do this?

A lot depends on how delta_X gets a new value. There are no functions to directly value a float based on analog or digital input, so the input data was an integer at some point.

I do not want to compare this value with a temp every time because it would be expensive.

Define expensive. Comparing values within a tolerance requires two ifs, and a jump is either is true (or not true).