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joseph20480
Joined: 21 Dec 2011
Posts: 42
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| Timer2 on pic 18f4550 with PLL5 (USB) |
 Posted: Sun Feb 19, 2012 2:29 pm |
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Hi,
I use a pic 18f4550 with a 20Mhz cristal... with fuses and code from CCS, I'm able to communicate in CDC mode with the pc (PLL for USB).
| Code: | #fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL5,CPUDIV1,VREGEN,PUT,BROWNOUT
#use delay(clock=48M) |
Now, i could use interruption of timer2 for generate a pwm signal... But i can't setting it correctly.
| Code: | setup_timer_2(T2_DIV_BY_1,1,1);
set_timer2(0);
enable_interrupts(global);
enable_interrupts(INT_TIMER2); |
T2_div_by_1 or T2_div_by_16.... any change...I don't understand what happen... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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Ttelmah
Joined: 11 Mar 2010
Posts: 19554
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| Posted: Sun Feb 19, 2012 3:40 pm |
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Also, as a comment, if you did want to use an interrupt off timer2 (nothing to do with PWM), the values used would prevent the chip doing _anything_ useful.
T2_DIV_BY_1 means run timer2, off the master oscillator/4 (one instruction per count). Then you are telling the timer to reset after just 2 counts (the '1' in the next location, plus one), and to interrupt every time the timer resets (the final '1'). Result, would be an interrupt every 2 instructions. Since it takes about 60 instructions to actually get into and out of an interrupt handler, the chip would sit permanently jumping into the interrupt handler.....
Ouch...
Best Wishes |
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