Notes

Experiment 3

part 1 :Generate Square Wave
having 50% duty cycle
using Timer1

ISIS:
RA0: connected to OSCilloscpe
(pin A)

------
code :
#include "ee470.h"
void main(void)
{
float fosc, Tosc, Tmc, f, T, Ttoggle;
unsigned int Ntoggle, ntmr1;
unsigned char t1h, t1l;
ADCON1=0xF; OSCCON=0x70; // 8MHz internal clk
TRISA0 = 0;
PORTAbits.RA0 = 0; // o/p pin
T1CON = 0x0; // T1:int. clk, no prescale, TMR1ON=0
fosc=8e6; Tmc=4*1/fosc; f=1e3; T=1.0/f; Ttoggle=T/2;
Ntoggle=(unsigned int) (Ttoggle/Tmc);
ntmr1=(0xFFFF+1)-Ntoggle;
t1h=ntmr1/256; t1l=ntmr1%256;
TMR1IF = 0;
T1CONbits.TMR1ON = 1;
while(1)
{
while (TMR1IF == 0);
PORTAbits.RA0 = ~PORTAbits.RA0;
TMR1H=t1h; TMR1L=t1l;
TMR1IF=0;
}
}
############
part 2 :
Generate Variable Duty Cycle
Square Wave using Timer1
**produce on pin RA0 a
periodic signal of period 1ms and duty
cycle=70%.

ISIS:
RA0:with pin A on OScilloscope

------
code:
#include "ee470.h"
void main(void)
{
float fosc, Tosc, Tmc, f, T;
unsigned int ntmr1onplusoff, ntmr1on, ntmr1off;
unsigned char t1hon, t1lon, t1hoff, t1loff;
ADCON1=0xF; OSCCON=0x70;
TRISA0 = 0;
PORTAbits.RA0 = 0;
T1CON = 0x0;
fosc=8e6; Tmc=4*1/fosc; f=1e3; T=1.0/f;
ntmr1onplusoff=(unsigned int) (T/Tmc);
ntmr1on=(0xFFFF+1)-ntmr1onplusoff*0.7;
ntmr1off=(0xFFFF+1)-ntmr1onplusoff*0.3;
t1hon=ntmr1on/256; t1lon=ntmr1on%256;
t1hoff=ntmr1off/256; t1loff=ntmr1off%256;
TMR1IF = 0;
T1CONbits.TMR1ON = 1;
while(1)
{
while (TMR1IF == 0);
PORTAbits.RA0 = 1;
TMR1H=t1hon; TMR1L=t1lon;
TMR1IF=0;
while (TMR1IF == 0);
PORTAbits.RA0 = 0;
TMR1H=t1hoff; TMR1L=t1loff;
TMR1IF=0;
}
}
------------
part3: Measuring the ON time
of a square pulse
*measure the ON time of a pulse
(half duration of a square wave)
applied to pin RD0.

ISIS:
pin 25:connected to Virtual terminal
pin 19:to signal generator(sin)
pin 30:to led to res=330 to gnd and
to signal generator (square wave)
-----
code:
#include "ee470.h"
void main(void)
{
unsigned int duration;
float fd;
OSCCON=0x40;
ADCON1=0xF;
serial_init(201,1);
;
TRISD0=1;
TRISD7=0;
RD7=0;
T1CON=0b00000000;
TMR1H=0;
TMR1L=0;
while(RD0==0);
RD7=1;
TMR1ON=1;
while(RD0==1);
TMR1ON=0;
duration=TMR1H*256+TMR1L;
fd=duration*4.0/fosc;
printf("duration in machine cycles=%u and in usec=%f rn",duration, fd);
printf("Frequency in Hz=%frn",1000000.0/fd/2);
while(1);
}
---------------
part 4:Use T1 to measure on-time
and oFF-time of a variable
duty cycle of a periodic signal

ISIS:
RA0: connected to oscilloscope
(pin A)
-----
code:
#include "ee470.h"
void main(void)
{
float ttick, on_time, off_time, period;
unsigned char tonl, tonh, toffl, toffh;
OSCCON=0x70;
ADCON1=0xF;
serial_init(51,1);
ttick=4.0/(fosc);
;
TRISD0=1;
TRISD7=0;
RD7=0;
T1CON=0b00000000;
TMR1ON=1;
while(RD0==1);
while(RD0==0);
RD7=1;
TMR1H=0;
TMR1L=0;
while(RD0==1);
tonl=TMR1L; tonh=TMR1H;
while(RD0==0);
while(RD0==1);
RD7=0;
TMR1H=0;
TMR1L=0;
while(RD0==0);
toffl=TMR1L; toffh=TMR1H;
on_time=(tonh*256+tonl)*ttick;
off_time=(toffh*256+toffl)*ttick;
printf("on time=%g off time=%g nr",on_time,off_time);
period=on_time+off_time;
printf("period in sec = %g, frequency in Hz=%grn",period,1.0/period);
while(1);
}