Here are few examples related
to various data typed in AVR. These are examples to get one started with using
data types.
Data Types revisited
|
Data Type
|
Size in Bits
|
Data Range/Usage
|
|
Unsigned char
|
8 bit
|
0 to 255
|
|
Char
|
8 bit
|
-128 to +128
|
|
Unsigned int
|
16 bit
|
0 to 65535
|
|
Int
|
16 bit
|
-32768 to +32768
|
|
Unsigned long
|
32 bit
|
0 to
4,294,967,295
|
|
Long
|
32 bit
|
-2,147,483,648 to +2,147,483,648
|
|
Float
|
32 bit
|
1.175e-38 to
3.402e38
|
|
Double
|
32 bit
|
1.175e-38 to 3.402e38
|
Using Unsigned Char
|
Examples
|
|
Example 1
|
|
//send values 00 - ff to say port B
#include <avr/io.h> //
standard avr header file
int main(void)
{
unsigned
char x;
DDRB
= 0xFF; // making all pins of port b as output
for(x
= 0; x<=255; x++)
{
PORTB
= x;
}
while(1);
//remember
x cannot store value > 255 as its an unsigned char
}
|
|
Example 2
|
|
// toggle pins of port b 100 times
#include <avr/io.h> //
standard avr header file
int main(void)
{
unsigned
char x;
DDRB
= 0xFF; // making all pins of port b as output
PORTB
= 0xAA; // port b 10101010
for(x
= 0; x<=100; x++)
{
PORTB
= ~PORTB;
}
while(1);
//remember
x cannot store value > 255 as its an unsigned char
}
|
Using Signed Char
|
Example
|
|
// program to
send values -2 to 2 to port B
#include
<avr/io.h>// standard avr header file
int main(void)
{
char num[] = {-2,-1,0,1,2};
unsigned char x;
DDRB = 0xFF;
// make all pins of port b
output
for(x = 0; x<5; x++)
{
PORTB =
num[x];
}
while(1);
//remember num can store value
between -128 to +128
// and array in C starts for 0
}
|
Similarly we can use other
data types. Here is toggling example at various values. Demonstrating when to
use what type.
|
Examples
|
|
Unsigned int
|
|
// toggle pins of port b 50000 times
#include <avr/io.h> //
standard avr header file
int main(void)
{
unsigned
int x;
DDRB
= 0xFF; // making all pins of port b as output
PORTB
= 0xAA; // port b 10101010
for(x
= 0; x<=50000; x++)
{
PORTB
= ~PORTB;
}
while(1);
//remember
x cannot store value > 65535 as its an unsigned int
}
|
|
Unsigned long
|
|
// toggle pins of port b 5,00,000
times
#include <avr/io.h> //
standard avr header file
int main(void)
{
unsigned
long x;
DDRB
= 0xFF; // making all pins of port b as output
PORTB
= 0xAA; // port b 10101010
for(x
= 0; x<=500000; x++)
{
PORTB
= ~PORTB;
}
while(1);
//remember
x can have value < 2,147,483,648 as
its an unsigned long
}
|
Time Delay can be created
1) Using
a simple for loop
2) Using
predefined C functions
3) Using
AVR timers
I don’t use a simple for loop
unless if its value is given along with the driver library. I only use
predefined C function to create delay.
|
Using predefined
C function to create a delay
|
|
//create 10 milli
sec delay
#include
<util/delay.h>
#include
<avr/io.h>
// delay in
milliseconds
void delay_ms(unsinged
int t)
{
_delay_ms(t);
}
int main(void)
{
DDRB = 0xFF;
//port b output
while(1)
{
PORTB = 0xFF;
delay_ms(10);
PORTB = 0X55;
delay_ms(10);
}
}
|
