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CheAhMeD
Joined: 10 Apr 2011
Posts: 4
Location: Tunisie
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| Help with PWM on PIC16F876 or 16F877 |
 Posted: Sun Apr 10, 2011 7:59 pm |
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Hello,
I doing a project to control the speed of a powrful DC Motor
I'm using 2 push buttons and PWM from a 16F877 to adjust the speed
I wrot the following program and compile it but I didn't get the PWM out of the CCP1 pin in fact there is no signal even for the LCD
I'm really confused since I'm a beginner 
I really need your help
| Code: |
#include <16F876.h>
#device adc=8
#use delay(clock=4000000)
#fuses NOWDT,XT, NOPUT, NOPROTECT, BROWNOUT, LVP, NOCPD, NOWRT, NODEBUG
#include <LCD.C>
#define Bouton1 PIN_C3
#define BOUTON2 PIN_C4
void convert_to_pourcent( long int data, char volts[6]) {
BYTE i;
long int temp,div;
div=1000;
for(i=0;i<=2;i++) {
temp=data/div;
volts[i]=(BYTE)temp+'0';
temp=div*(BYTE)temp;
data=data-temp;
div=div/10;
}
}
void display_data( long int data ) {
char volt_string[6];
convert_to_pourcent( data, volt_string );
printf(lcd_putc,volt_string);
lcd_putc(" % ");
}
void main()
{
long int r;
r=500;
output_c(0xF8);
set_tris_c(0xF8);
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_spi(FALSE);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_2(T2_DIV_BY_16, 127, 1);
lcd_init();
do{
setup_ccp1(CCP_PWM);
set_pwm1_duty(r);
lcd_putc("\f La vitesse actuelle du moteur est :");
lcd_gotoxy(1,2);
display_data(r);
if (input(bouton1) ==0) { r=r+10;set_pwm1_duty(r);lcd_gotoxy(1,2);display_data(r);delay_ms(50);}
if (input(bouton2) ==0) { r=r-10;set_pwm1_duty(r);lcd_gotoxy(1,2);display_data(r);delay_ms(50);}
if (r> 1000 ) {r=0;}
}
while (true);
}
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Thank you so much  |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Apr 10, 2011 10:10 pm |
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If something doesn't work, make a very simple test program that tests
only one thing. See if it works. For example, here is a program to
test PWM on the CCP1 pin. Test it, exactly as shown, with no changes.
| Code: |
#include <16F877.h>
#fuses XT, NOWDT, PUT, BROWNOUT, NOLVP
#use delay(clock=4000000)
//==========================
void main()
{
setup_timer_2(T2_DIV_BY_16, 255, 1);
setup_ccp1(CCP_PWM);
set_pwm1_duty(128); // 50% duty cycle
while(1);
} |
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John P
Joined: 17 Sep 2003
Posts: 331
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| Posted: Mon Apr 11, 2011 6:29 am |
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| Have you got pullup resistors on your pushbuttons? And why not use Port B, which has internal ones? |
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CheAhMeD
Joined: 10 Apr 2011
Posts: 4
Location: Tunisie
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| Posted: Mon Apr 11, 2011 6:32 am |
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| PCM programmer wrote: | If something doesn't work, make a very simple test program that tests
only one thing. See if it works. For example, here is a program to
test PWM on the CCP1 pin. Test it, exactly as shown, with no changes.
| Code: |
#include <16F877.h>
#fuses XT, NOWDT, PUT, BROWNOUT, NOLVP
#use delay(clock=4000000)
//==========================
void main()
{
setup_timer_2(T2_DIV_BY_16, 255, 1);
setup_ccp1(CCP_PWM);
set_pwm1_duty(128); // 50% duty cycle
while(1);
} |
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Hello PCM programmer and thank you for responding
I did exactly what you told me to do and still nothing on the CCP1 (PIN_C2) there is no signal :( |
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CheAhMeD
Joined: 10 Apr 2011
Posts: 4
Location: Tunisie
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| Posted: Mon Apr 11, 2011 6:33 am |
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| John P wrote: | | Have you got pullup resistors on your pushbuttons? And why not use Port B, which has internal ones? |
Yes I did put resistors on both push buttons and the port B is for the LCD |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Apr 11, 2011 11:48 pm |
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Does the PIC do anything ? Have you ever made it blink an LED ?
If you have no PWM signal, it could be because:
1. You have the LVP fuse enabled while not needing it, and pin B3 is
not connected to ground with a pull-down resistor, and is floating.
This causes the PIC to lock-up when pin B3 floats to a high level.
Solution: Change it to NOLVP.
2. The PIC is not running, because the oscillator is not working, or the
PIC is held in reset because the MCLR pin doesn't have a pull-up resistor
on it, or the PIC doesn't have power or ground connected to it.
3. The CCP1 pin may be connected to a very low resistance load
which the output driver on the PIC's CCP1 pin can't handle, and
therefore you see no PWM signal. The pin is loaded down too much.
Solution: Disconnect the load (the motor, or whatever it is). See if
you now get a signal. If so, you need an external driver for the motor. |
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CheAhMeD
Joined: 10 Apr 2011
Posts: 4
Location: Tunisie
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| Posted: Tue Apr 12, 2011 9:03 am |
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| PCM programmer wrote: | Does the PIC do anything ? Have you ever made it blink an LED ?
If you have no PWM signal, it could be because:
1. You have the LVP fuse enabled while not needing it, and pin B3 is
not connected to ground with a pull-down resistor, and is floating.
This causes the PIC to lock-up when pin B3 floats to a high level.
Solution: Change it to NOLVP.
2. The PIC is not running, because the oscillator is not working, or the
PIC is held in reset because the MCLR pin doesn't have a pull-up resistor
on it, or the PIC doesn't have power or ground connected to it.
3. The CCP1 pin may be connected to a very low resistance load
which the output driver on the PIC's CCP1 pin can't handle, and
therefore you see no PWM signal. The pin is loaded down too much.
Solution: Disconnect the load (the motor, or whatever it is). See if
you now get a signal. If so, you need an external driver for the motor. |
Hello PCM programmer,
I tried the program in ISIS in this circuit
It's a simple schematic but it doesn't work the pin CCP1 (PIN C2) is always blue (LOW 0v)
I'm really confused |
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