When programming an Arduino in C/C++ the line "DDRB |= 0b00101000;" occurs. While I know DDRB is the Data Direction Register for port B and the meaning of the numbers after "0b00" (which are the slots 13 to 9), I still don't really know what "0b00" means.
In definitions, I only read it means HIGH (while 0b11 means LOW), but what does that mean?
Full code:
#include <avr/io.h>
#include <util/delay.h>
int main (void) {
float seconds = 0.5;
int time = 1000 * seconds;
DDRB |= 0b00101000;
while (1) {
PORTB |= 0b00001000;
_delay_ms(time);
PORTB &= 0b11110111;
PORTB |= 0b00100000;
_delay_ms(time);
PORTB &= 0b11011111;
}
return 0;
}
0b means that a number in binary representation is expected.
For Data direction registers, setting the bits to 1 will make the respective lines outputs, and setting to 0 will make them inputs.
The DDRB |= 0b00101000 will do a binary OR operation between the current value of the bits in DDRB with the mask.
This will result in DDRB = 0b××1×1xxx, so that means DDRB will keep the value for lines 7 and 6. This operation basically sets lines 5 and 3 as Output and leaves the rest as they were.