Post by thread:16C73 PWM

I need to output a 50% Duty Cycle Fixed Frequency without tying up the processor. and I figured that the PWM might do the trick. Most of the app notes on the CD seem to relate to the 17C parts or the PWM theory. The Data Sheet doesn't give much detail on exactly what needs to be set up. Since I need to just output a fixed frequency do I need to setup the interrupts? - -Mark

> From: Mark Jurras <spam_OUTJURRAMTakeThisOuTtorrington.com> > > I need to output a 50% Duty Cycle Fixed Frequency without tying up the > processor. and I figured that the PWM might do the trick. Most of the app > notes on the CD seem to relate to the 17C parts or the PWM theory. The Data > Sheet doesn't give much detail on exactly what needs to be set up. > > Since I need to just output a fixed frequency do I need to setup the > interrupts? > > - -Mark > Assuming you are using a PIC16C7X (i.e. one with a PWM module), setting up for PWM output is documented quite well in the Microchip Datasheet for the 16C7X. Here is some code for PWM1: setup bsf status,rp0 movlw PWM_PERIOD movwf pr2 ; Set up period register bcf status,rp0 ; Optionally, set up TMR2 prescaler (not shown here) movlw 1<<tmr2on movwf t2con ; Turn on timer 2 movlw 0Ch movwf ccp1con ; Set PWM mode movlw PWM_PERIOD/2 ; Constant for 50% duty cycle movwf ccpr1l ; Set duty cycle ; Optionally, set 'fine control' bits for up to 10-bit resolution (not shown). ... turnoff clrf t2con ; Turn off timer 2 clrf ccp1con ; Turn of CCP 1. No interrupt handling is required. Regards, SJH Canberra, Australia

Steve, would you have some code to generate a sine wave using PWM on a 16C74??? What would be the highest frequency that could be generated under let say a 2% maximum armonic distortion??? thanks juan At 10:49 AM 10/3/96 EST, you wrote: {Quote hidden}>> From: Mark Jurras <.....JURRAMKILLspam@spam@torrington.com> >> >> I need to output a 50% Duty Cycle Fixed Frequency without tying up the >> processor. and I figured that the PWM might do the trick. Most of the app >> notes on the CD seem to relate to the 17C parts or the PWM theory. The Data >> Sheet doesn't give much detail on exactly what needs to be set up. >> >> Since I need to just output a fixed frequency do I need to setup the >> interrupts? >> >> - -Mark >> > >Assuming you are using a PIC16C7X (i.e. one with a PWM module), setting >up for PWM output is documented quite well in the Microchip Datasheet >for the 16C7X. Here is some code for PWM1: > >setup bsf status,rp0 > movlw PWM_PERIOD > movwf pr2 ; Set up period register > bcf status,rp0 >; Optionally, set up TMR2 prescaler (not shown here) > movlw 1<<tmr2on > movwf t2con ; Turn on timer 2 > movlw 0Ch > movwf ccp1con ; Set PWM mode > movlw PWM_PERIOD/2 ; Constant for 50% duty cycle > movwf ccpr1l ; Set duty cycle >; Optionally, set 'fine control' bits for up to 10-bit resolution (not shown). > ... >turnoff clrf t2con ; Turn off timer 2 > clrf ccp1con ; Turn of CCP 1. > >No interrupt handling is required. > >Regards, >SJH >Canberra, Australia > >

Juan Jose Abba wrote: > > Steve, would you have some code to generate a sine wave using PWM on a 16C74??? > What would be the highest frequency that could be generated under let say a > 2% maximum armonic distortion??? PWM and sine waves? Hmm, could you be a little more specific Juan? If you need a fast and accurate way to generate sine waves, then check out: http://www.interstice.com/~sdattalo/technical/software/pic/picsine.html If you need a REAL fast way to generate them and you are willing to give up a little accuracy then check out Eric Smith's: http://www.brouhaha.com/~eric/pic/sine.html As far as your 2% max armonic (harmonic) distortion, you might want to check out: http://www.interstice.com/~sdattalo/technical/theory/sinewave.html I discuss a little bit about how much error is introduced when you use first order linear interpolation with sine waves. Scott