Hi all im trying to control a servo using the timer interrupt. so when the 20ms interrrupt occurs a counter is incremented which sets the servo at a specific position which does happen however, i want it to change position when the second counter increments but this is not working... can any one help?

my code:

unsigned int count, Adcval;
unsigned int a =2000;

//Timer0
//Prescaler 1:256; TMR0 Preload = 100; Actual Interrupt Time : 19.968 ms

//Place/Copy this part in declaration section
void InitTimer0(){
  OPTION_REG         = 0x87;
  TMR0                 = 100;
  INTCON         = 0xA0;
}

void Interrupt(){
  if (TMR0IF_bit){
    TMR0IF_bit         = 0;
    TMR0                 = 100;
    count++;
  }
}


void main()
{
TRISB=0; // PORTB IS OUTPUT
PORTB=0;// PORTB INITIAL VALUE IS 0

ADC_init();

//count=0;
InitTimer0();
while(1)
{
if (count==1)
{
RB0_BIT=1;
//Adcval = ADC_Read(2);
Delay_us(500);
RB0_BIT=0;
//count=0;
TMR0=100;
}

if (count==2)
{
RB0_BIT=1;
//Adcval = ADC_Read(2);
Delay_us(1500);
RB0_BIT=0;
TMR0=100;
count=0;
}
}
}

Moderator edit: added code tags

 

Please tell us the model number of the MCU and which programming platform you are using.

 

RC servo? DC or BLDC motion servo? If the latter, nature of feedback device, if any??
Servo cover a wide gamut of devices!
Max.

 

its pic16f877a and easypic microelecronica on mikroc

 

Hi all im trying to control a servo using the timer interrupt. so when the 20ms interrrupt occurs a counter is incremented which sets the servo at a specific position which does happen however, i want it to change position when the second counter increments but this is not working... can any one help?

my code:

unsigned int count, Adcval;
unsigned int a =2000;

//Timer0
//Prescaler 1:256; TMR0 Preload = 100; Actual Interrupt Time : 19.968 ms

//Place/Copy this part in declaration section
void InitTimer0(){
  OPTION_REG         = 0x87;
  TMR0                 = 100;
  INTCON         = 0xA0;
}

void Interrupt(){
  if (TMR0IF_bit){
    TMR0IF_bit         = 0;
    TMR0                 = 100;
    count++;
  }
}


void main()
{
TRISB=0; // PORTB IS OUTPUT
PORTB=0;// PORTB INITIAL VALUE IS 0

ADC_init();

//count=0;
InitTimer0();
while(1)
{
if (count==1)
{
RB0_BIT=1;
//Adcval = ADC_Read(2);
Delay_us(500);
RB0_BIT=0;
//count=0;
TMR0=100;
}

if (count==2)
{
RB0_BIT=1;
//Adcval = ADC_Read(2);
Delay_us(1500);
RB0_BIT=0;
TMR0=100;
count=0;
}
}
}

Moderator edit: added code tags

Your post is confusing and just one big run on sentence "which does happen however," what does happen however?


Are you getting an output from RB0_BIT? Is your timer interrupt being called? Exactly what have you done to troubleshoot this issue?

And you have count=0 commented out so it is starting with an unknown value.

 

I do get an output and the servo turns to the specific position as counter reaches 1, however, when i set it to if count =2 then it just doesnt work and i think its probably because of timing that is wrong as the servo i have is standard and requires 20ms to turn to its position

 

//count=0;

Does not help. Why is it commented out?

 

This is your third thread about the same problem.
You should tell more about the circuit, type of the servos, power supply ( max current ) ...