Software pwm to drive RGB LED

[aghielan]

Hi i'm a newbie. I'm trying to develop software pwm to drive RGB LED using interrupt. but seems the code i developed doesn't works even the code was successfully compiled. Need experts help on my code. my code as below and i'm using HI TECH C v9.83. thanks in advance..

Code:

#include <htc.h>
__CONFIG(FOSC_INTRC_NOCLKOUT & WDTE_OFF& PWRTE_OFF & BOREN_OFF & LVP_OFF & WRT_OFF & DEBUG_ON & CPD_OFF & CP_OFF);
#ifndef _XTAL_FREQ
#define _XTAL_FREQ 8000000
#endif

#define RED_LED RD0 //red led
#define GRN_LED RD1 //green led
#define BLU_LED RD2 //blue led
#define ON 1
#define OFF 0
int red_dc, grn_dc, blu_dc, pulse = 0;
void init(void)
{
INTCON = 0b00100000;
TMR0 = 217;
ei();
}

void main(void) {
OSCCON = 0b1110001;
OPTION_REG = 0b00000000;
TRISD = 0b00000000; // 0=output
PORTD = 0b00000000;
TRISB = 0b11111111; // 1=input
ANSEL = ANSELH = 0;
red_dc = 256;
grn_dc = 1;
blu_dc = 256;

init();
while (1)
{
}
}

void interrupt isr(void){
di();
if(T0IF){

if(pulse==0 || pulse>256 )
{
pulse=0;
if(red_dc>0){ RED_LED=ON; }
if(grn_dc>0){ GRN_LED=ON; }
if(blu_dc>0){ BLU_LED=ON; }
}
else if(pulse>0)
{
if(pulse==red_dc){RED_LED=OFF;}
if(pulse==grn_dc){GRN_LED=OFF;}
if(pulse==blu_dc){BLU_LED=OFF;}
pulse++;
}
}
init();
}

 

[milind.a.kulkarni]

I think you forgot to run the timer check for that T0IE =1...

Good Luck

 

[aghielan]

Hi ,

I have set it under INTCON. Please help

INTCON = 0b00100000; //T0IE = 1

 

[milind.a.kulkarni]

One more suggation just make about clearing timer flag.... try this code.... I don't uses Hi tech -c .....but i had tried pwm in PIC....

void interrupt isr(void){
di();
if(T0IF){

if(pulse==0 || pulse>256 )
{
pulse=0;
if(red_dc>0){ RED_LED=ON; }
if(grn_dc>0){ GRN_LED=ON; }
if(blu_dc>0){ BLU_LED=ON; }
}
else if(pulse>0)
{
if(pulse==red_dc){RED_LED=OFF;}
if(pulse==grn_dc){GRN_LED=OFF;}
if(pulse==blu_dc){BLU_LED=OFF;}
pulse++;
}

T0IF=0; // Clearing timer flag
}
init();
}


Good Luck

 

[aghielan]

thanks.. i'll try it tonight..

 

[poorchava]

Why don't you use hardware OC module?

 

[aghielan]

i would like to drive 3 RGB LEDs, thats why i'm using software pwm. please advice

 

[poorchava]

I don't know HiTech compiler in detail, but one thing seems suspicious.

Your variable pulse is declared as int. I don't know if HiTech assumes signed integers unless explicitly stated 'unsigned'. Anyway you declare variable 'pulse' as int. Did you check if it doesn't overflow?

I also think you need to zero this variable at some point.

 

[slwthr]

One more suggation just make about clearing timer flag.... try this code.... I don't uses Hi tech -c .....but i had tried pwm in PIC....

void interrupt isr(void){
di();
if(T0IF){

if(pulse==0 || pulse>256 )
{
pulse=0;
if(red_dc>0){ RED_LED=ON; }
if(grn_dc>0){ GRN_LED=ON; }
if(blu_dc>0){ BLU_LED=ON; }
}
else if(pulse>0)
{
if(pulse==red_dc){RED_LED=OFF;}
if(pulse==grn_dc){GRN_LED=OFF;}
if(pulse==blu_dc){BLU_LED=OFF;}
pulse++;
}

T0IF=0; // Clearing timer flag
}
init();
}


Good Luck

I want to make a LED PWM circuit with using PIC. Please can you explain shortly how to do it?