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Phygraff
Joined: 25 Apr 2011
Posts: 1
Location: Lima, Peru
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| Using Timer1 as external pulse counter |
 Posted: Tue Apr 26, 2011 7:14 pm |
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I'm trying to use the timer1 feature of PIC18F2550 as a counter of external pulses (from a rotary encoder), but I'm not familiar with C programming. Anyone can help me with the basics?
Thanks.
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Luis A. Torres |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Apr 27, 2011 12:10 pm |
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CCS only has one example for using Timer1 as an counter with an
external clock source. I don't like, it's very messy:
| Quote: | | c:\program files\picc\examples\ex_freqc.c |
I don't have time today to write a more clean example. I have always
avoided using Timer1 in that mode, because there's an errata on it.
They have a work-around in the errata, but again, it would take me
some time to incorporate the errata and make a nice clean example
and I don't have time today. |
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ze.vana
Joined: 11 Jun 2011
Posts: 15
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| Posted: Sun Jun 12, 2011 4:47 am |
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| PCM programmer wrote: | CCS only has one example for using Timer1 as an counter with an
external clock source. I don't like, it's very messy:
| Quote: | | c:\program files\picc\examples\ex_freqc.c |
I don't have time today to write a more clean example. I have always
avoided using Timer1 in that mode, because there's an errata on it.
They have a work-around in the errata, but again, it would take me
some time to incorporate the errata and make a nice clean example
and I don't have time today. |
Hi
I've done this simple code using timer0 timer1 with external inputs T0CKI RA4/T1CKI RC0. I'm sure you it works, only problem it needs external circuit
to detect pulses A/B direction, I have Proteus photo diagram, don't know how to post it.
| Code: |
#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <lcd.c>
int16 T0,T1;
float R; //R is the result of Timer1 - Timer0
//I had to put a FLOAT insted INT16
void print_lcd(){ //because of LCD did not work well whith INT16,
lcd_init(); //I don't know why!
lcd_gotoxy(1,1);
printf(lcd_putc,"\f%g" R);
delay_ms(200);
}
void print_serial() {
t1=GET_TIMER1(); //get counter UP value
t0=GET_TIMER0(); //get counter DOWN value
R=T1-T0; //R is the actual encoder value
printf("\f R:%g T1:%Lu T0:%Lu ",R,T1,t0 );
delay_ms(200);
if(t0 > t1){ //prevent to not anti-clokwise first
SET_TIMER0(0);
SET_TIMER1(0);
}
}
#int_timer2
void timer_t2(){
static int tmp;
tmp++;
if(tmp <=5){ //it divides the timing of showing
print_lcd(); //LCD and serial
}
if(tmp>=5){
print_serial();
}
if(tmp>=10){
tmp=0;
}
}
void main(){
set_tris_a(0xff);
set_tris_b(0xff);
set_tris_c(0xff);
set_tris_d(0xff);
//TIMER0 16 bits as counter /DOWN- ext input T0CKI RA4
SETUP_TIMER_0(RTCC_EXT_H_TO_L|RTCC_DIV_1);
SET_TIMER0(0);
ENABLE_INTERRUPTS ( INT_TIMER0 );
ENABLE_INTERRUPTS ( GLOBAL );
// TIMER1 16 bits as counter /UP- ext input T1CKI RC0
SETUP_TIMER_1(T1_EXTERNAL | T1_DIV_BY_1 );
ext_int_edge(H_TO_L);
set_timer1(0);
enable_interrupts(int_timer1);
enable_interrupts(global);
//TIMER2 int
SETUP_TIMER_2(T2_DIV_BY_1,0xc0,2);
set_timer2(0);
enable_interrupts(int_timer2);
enable_interrupts(global);
while(true){
}
}
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