Timers

[sisif85]

Hi.

I have a problem. I'm trying to turn on a led for one second and after that to turn off the led, I want to use interrupts in order to do that. But using timers , I don't know how to set them up to overflow in 1000 ms. I saw that there are standards settings for that, but none of them are overflowing in 1000 ms.
Are some formulas for this type of settings? For example, the code that I wrote for turning on the led is this, but it doesn't respect what I should do.

#include <16F917.h>
#device ADC=10
#fuses HS,NOWDT,NOPROTECT
#use delay(clock=20000000)

#int_TIMER1
void clock_isr()
{
sec++;
if (sec==10) //trying to repete 10 times in order to get to that one second
{
output_high(PIN_D0);
sec=0;
}
if (sec==3) output_low(PIN_D0);
}

void main()
{
set_tris_d(0x00);
enable_interrupts(GLOBAL);
enable_interrupts(INT_TIMER1);
set_timer1(T1_INTERNAL | T1_DIV_BY_8); //overflows every 104.896 ms
while (TRUE) ;
}


I'll appreciate if you could help me.
Thanks in regards.

[ckielstra]

Use the 'Code' buttons when posting code in order to preserve formatting. Easier reading will give you more and quicker responses.

What is your compiler version number?

Bug: Variable sec is not defined nor initialized.

Tip: setting the TRIS register is not required, the CCS compiler will do this for you unless you specify #use fast_io.

The D0 output is multiplexed with COM3 for the LCD. Try disabling the LCD at the start of your program:

[rnielsen]

I would suggest you try using timer2. It has more pre/post scalers that will help you arrive at a correct delay.