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filjoa
Joined: 04 May 2008
Posts: 260
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| sleep mode and pwm on 18f252 |
 Posted: Wed Mar 18, 2009 12:21 pm |
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Hi
I make a little experiences and I like use sleep mode and pwm...
1º Sleep mode:
-on this chip (18F252) I can use a normal crystal with 20Mhz?
-for I can enter in sleep mode I only call the function sleep() but how I can wake up it? with an switch?
-if I need an switch where I connect them?
2ª PWM
I like add on my program some way for when I call for example flashled() put one led flash +-(500ms/500ms) and continue use program and led only stop when I give an order or something...
my start program configuration (missing pwm configuration, and sleep)
| Code: |
#include <18F252.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,BROWNOUT,STVREN
#use delay(clock=20000000)
#use rs232(baud=115200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
void main()
{
while (TRUE)
{
}
}
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some one can help me make this two examples?
kind regards |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Mar 18, 2009 4:35 pm |
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| Quote: |
for I can enter in sleep mode I only call the function sleep() but how I
can wake up it? with an switch? |
Download the 18F252 data sheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/39564c.pdf
Read these sections:
| Quote: |
19.3.1 WAKE-UP FROM SLEEP
19.3.2 WAKE-UP USING INTERRUPTS
3. Interrupt from INT pin, RB port change or a
Peripheral Interrupt.
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| Quote: |
I like add on my program some way for when I call for example
flashled() put one led flash +-(500ms/500ms) and continue use
program and led only stop when I give an order or something... |
This thread has sample code. It's possible that this code is too
complicated for you to use.
http://www.ccsinfo.com/forum/viewtopic.php?t=35429 |
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filjoa
Joined: 04 May 2008
Posts: 260
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| Posted: Wed Mar 18, 2009 7:15 pm |
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hi
so for WAKE-UP is better an switch and make reset... thanks
but question about PWM I don´t understand
if I active PWM with some frequency like an CCS example:
| Quote: |
// For a 20 MHz clock, 1.2 kHz frequency,
duty = 512; // .000416/(16*(1/20000000))
set_pwm1_duty(duty);
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1ª- if I have an led on pin CCP1 it flash with 1.2khz correct?
2ª- but if I go to other function make other task but don't change "set_pwm1_duty(duty)" led continue flashing correct?
3ª- led only stop flash if I make some like that:
| Quote: |
duty=0;
set_pwm1_duty(duty);
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if this 3 question stay correct I have a little problem... I don´t know on my program write the setup pwm (in code) for when I call set_pwm1_duty() program know what I stay call, I don´t understand this part.
regards |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Mar 18, 2009 9:32 pm |
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| Quote: | | I like add on my program some way for when I call for example flashled() put one led flash +-(500ms/500ms |
Here, you said you wanted 500 ms on, and 500 ms off (1 Hz flashing rate).
| Quote: | | if I have an led on pin CCP1 it flash with 1.2khz correct? |
Here, you change this to 1200 Hz. Why ? You will not see any flashing
at 1200 Hz. The human eye cannot detect 1200 Hz. You will see an
LED that is dim or bright, depending on the duty cycle.
What do you really want ? |
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filjoa
Joined: 04 May 2008
Posts: 260
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| Posted: Thu Mar 19, 2009 2:58 pm |
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this is an example... I copy direct from CCS help
I need (500ms on/500ms off) +- |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Thu Mar 19, 2009 3:34 pm |
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| It's no good example, cause 1200 Hz pwm frequency works, 1 Hz doesn't. You'll easily see why. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 19, 2009 3:47 pm |
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If you need an independent flashing routine, then create a Timer0
interrupt routine. Setup Timer0 to interrupt at some suitable low
rate, such as 20 Hz (50 ms). An interrupt rate of 2 Hz (500 ms) is
not possible, with your 20 MHz oscillator. Then put a static counter
variable inside the Timer0 interrupt routine. Initialize it to 0. Then
once every interrupt, increment the variable. When it reaches a
count of 10, then you have delayed for 500 ms (10 x 50 ms).
Toggle the LED at that time. Then reset the static variable to 0.
Initialize the static variable to 0 at the start of main(). Also set the
LED pin to output a low level at the start of main().
Also test a global flag inside the Timer0 interrupt routine. If the
flag variable is set to FALSE, then skip the toggling of the LED.
Instead, turn it off. If the global flag is true, then do the toggle. |
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filjoa
Joined: 04 May 2008
Posts: 260
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| Posted: Thu Mar 19, 2009 4:52 pm |
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| but how I can configure timer0, for have 20hz? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 19, 2009 4:55 pm |
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| Why don't you try to write the code ? You could learn something. |
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filjoa
Joined: 04 May 2008
Posts: 260
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| Posted: Wed Mar 25, 2009 3:42 pm |
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hi
I have a extract this little example, make with wizard option, but I don't understand how it work...
is example is for I control one DC engine.
in my case what I need to configure PWM?
| Quote: |
void frente()
{
printf("Frente\n\r");
set_pwm1_duty(1000);
set_pwm2_duty(1000);
}
void main()
{
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_16,255,1);
setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
setup_oscillator(False);
setup_ccp1 (CCP_PWM);
setup_ccp2 (CCP_PWM);
}
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filjoa
Joined: 04 May 2008
Posts: 260
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| Posted: Thu Mar 26, 2009 10:36 am |
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Hi
on wizard have this options:
there tell which information stay on timer2, someone can tell me how I can make calculation there "setup_timer_2(T2_DIV_BY_16,255,1); " for have +- 500ms/500ms?
kind regards |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 26, 2009 11:02 am |
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The lowest frequency for hardware PWM is 244 Hz (with 4 MHz crystal).
You can not get 1 Hz rate with hardware PWM. The Wizard can not help you.
You must use a software method. I described it in my earlier post.
But, you don't want to write any code. You only want "Wizard". |
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