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acm45
Joined: 29 Dec 2008
Posts: 18
Location: Italy
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| Pwm duty cycle strange behaviour! |
 Posted: Fri Sep 09, 2011 1:34 pm |
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Hi there!
I'm doing a small motor control with the classic H bridge controlled by a 18F4550 pic (with 20MHz and HSPLL active).
It works really well but, I noticed a strange behaviour, here's the code!
| Code: | setup_timer_0(RTCC_INTERNAL|RTCC_DIV_256|RTCC_16_BIT);
setup_timer_2(T2_DIV_BY_1,0xff,1); //25.0 us overflow, 25.0 us interrupt per generare la portante PWM 46kHz
setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
setup_ccp1(CCP_PWM_FULL_BRIDGE | CCP_PWM_H_H |CCP_SHUTDOWN_ON_INT0|CCP_SHUTDOWN_AC_L|CCP_SHUTDOWN_BD_L);
set_tris_d(0x1F);
set_tris_d(0x02);
set_pwm1_duty((int16)0x000F); |
The last instruction gives me a duty cycle of 0%!!!
If I write values from 0x000C to 0x000F I obtain the same wrong duty cycle!!! Moreover if the last 4bits have a value between 0xC and 0xF, the duty cycle is always 0%!
Writing 0x000A I obtain a duty cycle of 0.9% as expected!
I see the pwm registers and seem all ok with the right value as described in the datasheet.
Thank you in advance for your help! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Sep 09, 2011 1:45 pm |
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| What's your compiler version ? |
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acm45
Joined: 29 Dec 2008
Posts: 18
Location: Italy
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| Posted: Fri Sep 09, 2011 1:51 pm |
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| The compiler version is: 4.114 |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Sep 09, 2011 2:21 pm |
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I put this code in a standard small template with #include, #fuses, #use
delay, and main(), and it doesn't compile with vs. 4.114. The last
parameter is not in the 18F4550.h file. Therefore this is not real code.
| Quote: |
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_256|RTCC_16_BIT); |
Please post real tested code, with the #include, #fuses, #use delay(),
and main().
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Edit: Corrected a typo. I meant to say "not real code".
Last edited by PCM programmer on Sun Sep 11, 2011 1:17 pm; edited 1 time in total |
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acm45
Joined: 29 Dec 2008
Posts: 18
Location: Italy
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| SOLVED |
| Posted: Sun Sep 11, 2011 2:39 am |
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sorry for the parameter RTCC_16_BIT, I defined it into my 18F4550.h file as a 0x00. Anyway, I find the problem in my own code, setting the pwm duty cycle I was setting also the reverse bridge control.
Thank you for your help! |
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