MPLAB

molten_rock01 · **Posted:** Sat Jun 11, 2005 7:48 pm

Hi. I'm new at C and am doing a project for a class. My project partner just learned to use sub routines but we're having trouble. Could someone suggest what might be wrong?

code:

int a, b, c, x, portaval; // Declare variables for loop

main()
{
PORTA = 0;
PORTC = 0;
CMCON0 = 7;             // Turn off comparators
ANSEL = 0; // Turn off ADC
TRISA0 = 0;             // Make RA0/RA1/RA2/RA4/RA5/RC0/RC1/RC2/RC3/RC4/RC5 outputs
TRISA1 = 0;
TRISA2 = 0;
TRISA4 = 0;
TRISA5 = 0;
TRISC0 = 0;
TRISC1 = 0;
TRISC2 = 0;
TRISC3 = 0;
TRISC4 = 0;
TRISC5 =0;
TRISA3 = 1;             // Make RA3 input
a = 0;
b = 0;
c = 0;
x = 0;
portaval=x;

while (1==1) // Loop forever
{
if (RA3==1)          // button is pressed
{
b = b + 1; // Counter
} // fi

if (b==1)          // button is pressed for the first time
{
x = showrider();
blinkled(x);
}
else if (b==3) // button is pressed for the third time
{
x = showrider();
blinkled(x);
}
else if (b==5)   // button is pressed for the fifth time
{
x = showrider();
blinkled(x);
}
else if (b==7) // button is pressed for the seventh time
{
x = showrider();
blinkled(x);
}
else if (b==9) // button is pressed for the nineth time
{
x = showrider();
blinkled(x);
}
} //elihw
} // end main

int showrider()
/* Knight Rider Effect*/
{
while (RA3==1) // wait for the user to lift finger after pressing button
{
} // elihw

while (RA3==0) //while button is not being pressed
{
PORTA = 0b000001;
for (a=0; a<255; a++); // Simple delay loop
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
return 1;
}
PORTA = 0b000010;
for (a=0; a<255; a++); // Simple delay loop
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
return 2;
}
PORTA = 0b000100;
for (a=0; a<255; a++); // Simple delay loop
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
return 3;
}
PORTA = 0b010000;
for (a=0; a<255; a++); // Simple delay loop
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
return 4;
}
PORTA = 0b100000;
for (a=0; a<255; a++); // Simple delay loop
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
return 5;
}
} //elihw
}

void blinkled(portaval)
{
while (RA3==0) //while button is not being pressed
{
if (portaval==1)
{
while (1==1)
(
PORTA = 0b000001;
simpledelayloop();
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
break;
}
} //fi
}
}
else if (portaval==2)
{
while (1==1)
(
PORTA = 0b000010;
            simpledelayloop();
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
break;
}
} //fi
}
}
else if (portaval==3)
{
while (1==1)
(
PORTA = 0b000100;
            simpledelayloop();
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
break;
}
} //fi
} //elihw
}
else if (portaval==4)
{
while (1==1)
(
PORTA = 0b010000;
            simpledelayloop();
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
break;
}
} //fi
} //elihw
}
else if (portaval==5)
{
while (1==1)
(
PORTA = 0b100000;
            simpledelayloop();
if (RA3==1)
{
while (RA3==1)
{
}
while (RA3==0)
{
break;
}
} //fi
} //elihw
}
} //elihw
}

void simpledelayloop()
{
   for (a=0; a<255; a++) // Simple Delay Loop
      for (c=0; c<127; c++);
PORTA =0b000000;

}

When ever we build this program, the

code:

void blinkled(portaval)

gives a syntax error. We've looked over the code a thousand times.

the_short1 · **Posted:** Sat Jul 23, 2005 12:57 pm

can i suggest two things: make USER friendly variable names.. TRUST ME it makes it a LOT easier to debug..

and: go like

while (RA3==0){
}

i think you just got a bracket out of place.. hence the syntax error. happened to me all the time until i swithed the the cleaner way.. mkaes it easier to notice , i used MLAB Ide for programming our robot www.instigators1596.com

-kevin

wtd · **Posted:** Sat Jul 23, 2005 1:24 pm

Indeed. "a", "b", "c" and "portaval" are not meaningful variable names.

Use spaces.

Bad:

code:

if (foo==bar)

Good:

code:

if (foo == bar)

Don't use meaningless comparisons.

Bad:

code:

while (1 == 1)

Good:

code:

while (1)

Don't use global variables. Use local variables and pass them via function parameters.

Instead of long "if... else..." constructs that just compare one int, use a switch.

Bad:

code:

if (foo == 1)
{

}
else if (foo == 3)
{

}
else if (foo == 5)
{

}
else
{

}

Good:

code:

switch (foo)
{
case 1:
break;
case 3:
break;
case 5:
break;
default:
break;
}

On the other hand, you do the same thing every single time, so reduce your code's length via math.

Bad:

code:

if (b==1) // button is pressed for the first time
{
x = showrider();
blinkled(x);
}
else if (b==3) // button is pressed for the third time
{
x = showrider();
blinkled(x);
}
else if (b==5) // button is pressed for the fifth time
{
x = showrider();
blinkled(x);
}
else if (b==7) // button is pressed for the seventh time
{
x = showrider();
blinkled(x);
}
else if (b==9) // button is pressed for the nineth time
{
x = showrider();
blinkled(x);
}

Good:

code:

if (b % 2 == 1 && b >= 1 && b <= 9)
{
x = showrider();
blinkled(x);
}

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