Wrong Frequency

[gadelhas]

Hi Everyone;

I've got this code, and it's working fine, however the frequency of the pwm mesured with the oscilocope it's half the frequency configured.
It is suposed to have 5Khz, however i've got 2.5Khz.

Can anybody tell me what i'm doing wrong in the code?

PIC12F683

Define OSC 8
@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _BOD_OFF

  
'                                PINOUT 1 = IN; 0 = OUT
' ====================================================================
              '76543210
 TRISIO     = %00000001
 
              '76543210
   GPIO     = %00000000
   
 ANSEL = 1  'GP0 ANALOG             
 VRCON = 0  'VREF OFF
 CMCON0 = 7 'COMPARATOR OFF             
 ADCON0 = %10000000  'RIGHT JUSTIFY - 128
 
 PR2     = %00011000 'SET 24 - 5000Hz - 8Bits
 T2CON   = %00000110 'TIMER2 ON - PRESCALER 1:16 - Max Duty Value 100 - 1% Step
 CCPR1L  = %00000000
 CCP1CON = %00001100 'PWM ON

Thanks

[aratti]

You have to set the OSCCON register, since by default is set to 4 MHz and you define the osc as an 8 MHz one.

Cheers

Al.

[gadelhas]

Thank you aratti for the fast answer to my problem. I changed the OSCCON register, and it worked at the desired frequency.

Thank you once again!

[rsocor01]

Hmmm , I thought the DEFINE OSC x takes care of the frequency registers. I'm just curious, will it work if the internal oscillator is defined first and then the frequency is defined after that? In the next code, I just swapped the order of the first two lines in gadelhas original code.

@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _BOD_OFF

Define OSC 8
  
'                                PINOUT 1 = IN; 0 = OUT
' ====================================================================
              '76543210
 TRISIO     = %00000001
 
              '76543210
   GPIO     = %00000000
   
 ANSEL = 1  'GP0 ANALOG             
 VRCON = 0  'VREF OFF
 CMCON0 = 7 'COMPARATOR OFF             
 ADCON0 = %10000000  'RIGHT JUSTIFY - 128
 
 PR2     = %00011000 'SET 24 - 5000Hz - 8Bits
 T2CON   = %00000110 'TIMER2 ON - PRESCALER 1:16 - Max Duty Value 100 - 1% Step
 CCPR1L  = %00000000
 CCP1CON = %00001100 'PWM ON

Robert

[mackrackit]

The configs and the OSCCON register if using an internal OSC is for setting the hardware.
The PIC will then run at that speed. Run at the speed of the external OSC or the internal setup.

All
DEFINE OSC X
does is to tell PBP how fast the chip is running. DEFINE OSC X does not set the chips speed.

Because the two are completely different things the order does not matter.

[rsocor01]

The configs and the OSCCON register if using an internal OSC is for setting the hardware.
The PIC will then run at that speed. Run at the speed of the external OSC or the internal setup.

All
DEFINE OSC X
does is to tell PBP how fast the chip is running. DEFINE OSC X does not set the chips speed.

Because the two are completely different things the order does not matter.

Ooh, I see. Dave thank you for your help.

Robert