This bunch of code gives me 6 errors upon attempt to compile. Basically it's a 'nightrider' (or whatever the internet calls it nowadays) thingy which flashed LEDs from LED0 to LED7 and then back in a sequential order . The only modification is that I have 2 buttons which manually change the direction of flashing .

There is a left button and a right button . If the pattern is progressing to the right and I press the left button , then it changes direction to the left starting from the led that was active when I pressed the button . If I press the right button while it's travelling right then nothing happens .
Vice versa for the other side.

#include <avr/io.h>
#include <util/delay.h>

int x=0;
int y=0;

int roamleft(int x);
int roamright(int y);


DDRB = 0b11111111;
DDRD = 0b00000011;

PORTD = 1<<PIND2 | 1<< PIND3;
	


int main(void)
{
   
   	

	
   	while(1)
   	{
	
		x = roamright(y); // flash to the right  sequentially from LED Y to LED 7
		y = roamleft(x);  // flash  to the left   sequentially from LED X to LED 0
		  	   
    }
	
	   	
}

int roamright(y)
{ 
	for(x=y;x<8;x++)    // cycles through the LED ports
	{
	PORTB = 1 << x;     // Flash the led
	_delay_ms(100);     // delay before flashing next led
	PORTB = 0;          // Turn LED port off
	if(bit_is_clear(PIND,2))   // Test if button pressed
	{
		return x;             //break the cycle and call 'roamleft' carrying in the value that the led stopped at.
	}
	
	}
	
	return x;                 // if button is not pressed , then x=7 will be carried into 'roamleft' so it starts to flash to the left sequentially starting from LED 7
	
		
		
}

int  roamleft(x)
	{
		

	for(y=x;y>=0;y--)
	
	{
		
	PORTB = 1 << y;
	_delay_ms(100);
	PORTB = 0;
	
	if(bit_is_clear(PIND,3))
	{
		return y;
	}
	
	
	}
	 return y;
	
}
Select All

Can someone just skim through that and tell me if there are any coarse syntax errors or whatever that cannot be done the way I did it , i'd appreciate it.
I'm using Atmel studio 6. It tells me I have 6 errors but It doesn't show me where they are.
Thanks in advance


I've had some experience in C++ and java in the past but some things confuse me here.
Why do I see functions declared in some tutorials and others just omit it? Does it depend on the compiler or something?

 

Hmm apparently I'm supposed to declare the DDRB and D registers in the main function ...
I thought that i've been doing it outside it all the time .

 

works pretty nicely

 

...I tried pointing that out, but my phone kept getting feisty worth me, so I figured someone else could do it.

You are attempting to set the value of a register, not set a fuse. Modifying register contents is done in the program...

Glad to hear it's working now...

 

Well, thanks for the attempt anyway

 

I think the code is complex and could be simplified a lot.

Here's one quick option to get the same effect, this is the whole code and needs to go in main();

unsigned char right;

PORTB = 0x01;
right = 0;
while(1)
{
  Delay_mS(100);
  if(right)
  {
    PORTB = (PORTB >> 1);           // shift right
    if(PORTB == 0x01) right = 0;    // and test for reached the end
  }
  else     
  {
    PORTB = (PORTB << 1);           // shift left
    if(PORTB == 0x80) right = 1;    // and test for reached the end
  }
}

 

I think the code is complex and could be simplified a lot.

Here's one quick option to get the same effect, this is the whole code and needs to go in main();

hmm I cannot see the button inputs in that piece of code .

 

Adding in an interrupt that changes the value of the direction flag (right) depending on the button wouldn't be much more work...

 

Yes , thing is I don't know how to use interrupts yet .
I want to do one more program that I have in plan with led's using PWM with normal I/0 before I go into using counters and interrupts

 

Yes , thing is I don't know how to use interrupts yet .

You've got a good reason to learn!

 

Well when I started out , I just started going over all the aspects ofc the MCU without trying them all out in practice (mostly due to crappy tutorials) and I kept getting pissed off at all these features because I didn't know what they were good for .
I mean why the F is there a PWM mode when I can make PWM with I/0 and delays right??
Ok .... I know now after MrChips explained but more importantly I know now because when I tried to create certain programs with I/0 I ran into limitations where the concept of ínterrupts started making sense , so I decided to take it step by step