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denis_11
Joined: 13 Jul 2010
Posts: 45
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| 2 pwm...is it possible? |
 Posted: Thu Jul 15, 2010 6:15 am |
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Hello I am doing multiple tests 18f14k50 and I'm trying to generate two PWM ... CCS shows me as the availability of 3 CCP use those to generate two frequencies of 1 MHz and 1,5mHz? I use a 48MHz quartz ...
| Code: |
setup_timer_1(T1_DIV_BY_1);
setup_timer_2(T2_DIV_BY_16,255,1);
setup_ccp1(CCP_PWM);
setup_ccp2(CCP_PWM);
set_pwm1_duty(16);
set_pwm2_duty(18);
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I tried this two frequencies to generate any frequencies but only works RC5 ... why?
Last edited by denis_11 on Thu Jul 15, 2010 1:19 pm; edited 1 time in total |
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denis_11
Joined: 13 Jul 2010
Posts: 45
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| Posted: Thu Jul 15, 2010 10:29 am |
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| nobody has ever used the pwm? I just wanted to know if it was possible to obtain with this pic two pwm |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jul 15, 2010 11:50 am |
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Read the data sheet. Type this into Google:
| Quote: | | PIC18F14K50 site:microchip.com |
That quickly gets you the link to the page for the 18F14K50.
From there you can download the data sheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/41350D.pdf
Look at pages 3 and 4 for a summary of the peripherals on the PIC:
| Quote: |
• Enhanced Capture/Compare/PWM (ECCP) module:
- One, two, three, or four PWM outputs
- Selectable polarity
- Programmable dead time
- Auto-shutdown and Auto-restart
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| Code: |
ECCP
(pwm)
PIC18F14K50 1
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The answer is: There is only one PWM module on the PIC (CCP1).
However, the same PWM signal can be output on 1 to 4 pins. This is
called "pulse steering" mode.
If this is what you want to do, then post your compiler version. |
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denis_11
Joined: 13 Jul 2010
Posts: 45
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| Posted: Thu Jul 15, 2010 1:17 pm |
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| My compiler version is 4.106 and I want to generate two different frequencies ... one of 1 MHz and a second of 1.5 MHz ... then I would also use the comparator simultaneously ... you say that this is possible? I do not know what to do ... you have an example to show me? thanks |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jul 15, 2010 1:44 pm |
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| Quote: |
I want to generate two different frequencies ... one of 1 MHz and a
second of 1.5 MHz.
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You need 2 hardware CCP modules to do that. The 18F45K50 only has
one CCP module.
You need to use a PIC that has two separate CCP modules (CCP1 and CCP2). |
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denis_11
Joined: 13 Jul 2010
Posts: 45
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| Posted: Thu Jul 15, 2010 2:07 pm |
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| ah ok ... and with a 18F2550 can generate two different frequencies? it has 2 CCP... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Jul 15, 2010 2:56 pm |
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Actually that's not going to work. You need two PWM modules, but each
one must have it's own separate timebase. Some PICs have this.
The 18F2520 does not. Both PWM channels run off Timer2 in that PIC.
The 18F4431 series does have two separate Timebases for PWM:
http://www.ccsinfo.com/forum/viewtopic.php?t=37206
There are some other PICs that also have this.
But with two PWM frequencies of 1 MHz and 1.5 MHz, the duty cycle
range will be very small. You won't get 256 PWM levels. You'll just
get a few. Also, you'll need to use a 12 MHz or 24 MHz crystal.
Are you sure you want to do this ? What's the purpose of your project ? |
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