I am working on atmega 8 .I am new to it ,and making a program that will
glow a led on one pin depending on the input in another pin ie if input
is 5v led will glow otherwise it will not.But i guess something is wrong
with my program.
#define F_CPU 1000000UL
#include <avr/io.h>
#include <util/delay.h>
int main (void)
{DDRB=0x03;
PORTB=0x00;
while(1)
{
if(PINB && 0b00000001)
PORTB=0x02;
else
PORTB=0x00;
}}
:
Moved by Moderator
“&&” is a logical AND. What you (probably) want is a bitwise AND though, which is “&”.
After few days i was able to overcome the problem in the code,my new
code:
#define F_CPU 1000000UL
#include <avr/io.h>
int main(void) {
DDRC = 0xFF;
DDRB = 0;
PORTB = 0;
PORTC=0b00000000;
while (1) {
if(PINB==0b00000001)
PORTC = 0b00000001;
else
PORTC=0;
}
}
But still there is some problem,the led is turning off when i connect
the input to ground but when the input is not grounded the led glows and
when input is connected to 5v led glows but slight brightly.I want to
know why is led not turning off completely when there is no
input(neither ground nor 5v).
because it is a common misconception, that an input pin, which is not connected to anything, gives a value of 0. In fact, that pin is nothing more then an antenna, which reacts on any electromagnetic field nearby. And there are lots of them. Eg all the power cords in the wall, your mobile phone, ther µc itself, etc. etc. Exactly this is, why we use pullup or pulldown resistors, which guarantee a specific value on an input portpin, even if the usual switch is not closed.
1 | #define F_CPU 1000000UL
|
2 | #include <avr/io.h> |
3 | |
4 | int main(void) { |
5 | |
6 | DDRC = 0xFF; |
7 | DDRB = ( 1 << PB0 ); // turn on pullup resistor |
8 | // to guarante, that the portpin will
|
9 | // give a 1 Bit, even if there ist nothing
|
10 | // connected to it
|
11 | |
12 | |
13 | PORTC = 0b00000000; |
14 | |
15 | while (1) { |
16 | if( PINB & ( 1 << PB0 ) ) |
17 | PORTC |= ( 1 << PC0 ); |
18 | else
|
19 | PORTC &= ~( 1 << PC0 ); |
20 | |
21 | }
|
22 | }
|
and familiarize yourself with C-bitoperations. They are your 'working horse' in µC-programing!
Sorry. My fault
1 | #define F_CPU 1000000UL
|
2 | #include <avr/io.h> |
3 | |
4 | int main(void) { |
5 | |
6 | DDRC = 0xFF; |
7 | PORTB = ( 1 << PB0 ); // turn on pullup resistor |
8 | // to guarante, that the portpin will
|
9 | // give a 1 Bit, even if there ist nothing
|
10 | // connected to it
|
you need to set a 1 Bit in the PORTx Register, to turn on the pullup resistor for that pin, if the pin is an input pin.
Thanks...can you suggest me a source from where i can learn basic c-bit operations,i know how to use them but find it little confusing when using it with avr.
Well. Any C Progamming book should do. Unfortunately I don't know any english written Tutorial for the topic of bit-operations. In a Nutshell: to turn a bit to 1
1 | register |= ( 1 << bitnumber ); |
to turn a bit to 0
1 | register &= ~( 1 << bitnumber ); |
to check if a bit is 1
1 | if( register & ( 1 << bitnumber ) ) |
to check if a bit is 0
1 | if( !(register & ( 1 << bitnumber ) ) |
look up the operators & | << >> and ~ in the C textbook of your choice.
If you know russian i can send you a very detailed tutorial in russian about the avr and really simple examples and how to use them..
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