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Chapter 3b3 - Simple LED Project (continued) |
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The next statement in the main() function is the start of a
while loop. A
while loop performs a repeated operation while some condition
contained within the parenthesizes is TRUE (or not FALSE
depending how you look at things). While
loops can repeat single statements or multiple statements as
shown in the following examples.
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Example #1 |
while( 1 ); |
This is an infinite loop because the constant 1 as
the argument for the while statement evaluates to TRUE
and there is no further statements to execute because
the statement is terminated with the semicolon (;).
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Example #2 |
while( 1 ) do_function1(); |
This is another infinite loop but in this case the
function do_function1() is continually executed.
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Example #3 |
while( 1 )
{
do_function1();
do_function2();
}
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This while loop again goes on forever but shows how
multiple statements can be executed, in this case 2
functions. The brackets enclose all the statements
associated with the while loop.
Note : Try to adopt this general format for while
loops because numerous organizations consider this easy
to understand. |
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Example #4 |
x = 0;
while( x < 10 )
{
delay_msec( 50 );
x = x + 1;
}
do_more_function();
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Now we have a while loop with a condition associated
with it. Notice that the while is executed while the
variable x is less than 10. When the variable x equals
or exceeds 10 then the while loop is terminated and the
program continues. More on variables later in the
projects. |
Now that a basic while loop is understood, the 4 statements
that are executed continuously do the following;
- Set the output port pin C2 high which turns on the LED
- Delay
- Set the output port pin C2 low which turns off the LED
- Delay
- go back to #1
The _delay() function provides a delay of instruction
cycles and is rather crude for now. A better delay function
will be developed in a following section.
Try this program out.
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