Futaba S3004
--- John Ferrell <johnferrell@EARTHLINK.NET> wrote:
> What kind of servo (brand/model).
> John Ferrell
> 6241 Phillippi Rd
> Julian NC 27283
> Phone: (336)685-9606
> johnferrell@earthlink.net
> Dixie Competition Products
> NSRCA 479 AMA 4190  W8CCW
> "My Competition is Not My Enemy"
>
> ----- Original Message -----
> From: "Joel Middleton" <chopsuey1973@YAHOO.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Sunday, June 15, 2003 1:12 PM
> Subject: Re: [PIC]: Servo Pulse Problem
>
>
> > I found this schematic on the web and this is my
> exact
> > circuit except the servo signal is connected to
> pin 3
> > on portb. Also I have all the unused pins
> connected to
> > ground. Anyone see anything wrong with the
> circuit?
> >
> >
> > --- rneel@COX.NET wrote:
> > > I'm certainly no expert, but it looks like a
> classic
> > > capacitor discharge issue to me.  If you have a
> cap
> > > on this output, it will take time for it to
> > > discharge causing the slow decay in voltage
> instead
> > > of a nice sharp corner.  I can't see your
> circuit
> > > but do you have a cap connected across the pin
> you
> > > measured with the scope?
> > > >
> > > > From: Joel Middleton <chopsuey1973@YAHOO.COM>
> > > > Date: 2003/06/15 Sun AM 01:21:50 EDT
> > > > To: PICLIST@MITVMA.MIT.EDU
> > > > Subject: [PIC]: Servo Pulse Problem
> > > >
> > > > I believe I am having a problem with the pulse
> I
> > > am
> > > > sending to a servo connected directly to portb
> pin
> > > 3.
> > > > I have tmr0 set to overflow ever .0001
> seconds.
> > > The
> > > > variable 'count' is incremented each time tmr0
> > > > overflows when count reaches 200 it is reset
> to 0.
> > > > When count is equal to zero I set portb pin 3
> and
> > > when
> > > > count equals pw1 I clear the pin. I believe
> this
> > > > should give me a 1ms pulse every 20ms. This
> was
> > > not
> > > > working like I thought and I wanted to take a
> look
> > > at
> > > > the pulse so I downloaded one of those
> > > ocilloscopes
> > > > that runs through a sound card as I did not
> have
> > > > access to a real one. Well I found out that I
> am
> > > not
> > > > getting a nice square wave. The rising edge
> looks
> > > fine
> > > > but the falling edge is a slope. Can anyone
> tell
> > > me
> > > > how to correct this? I have included my code
> and
> > > also
> > > > attached an image I captured from the
> occiloscope.
> > > > Thanks.
> > > >
> > > >
> > > > LIST R=DEC
> > > >
> > > > INCLUDE "p16f84a.inc"
> > > >
> > > > CBLOCK 0x0C
> > > > _w
> > > > _status
> > > > _pclath
> > > > _fsr
> > > > count
> > > > pw1
> > > > ENDC
> > > >
> > > > __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC &
> _PWRTE_ON
> > > >
> > > > push    macro
> > > >         movwf   _w                      ;Save
> > > registers
> > > >         movf    STATUS, w
> > > >         movwf   _status
> > > >         movf    PCLATH, w
> > > >         movwf   _pclath
> > > >         clrf    PCLATH
> > > >         endm
> > > >
> > > > pull    macro
> > > >         swapf   _pclath, w
> > > >         movwf   PCLATH
> > > >         movf    _status, w      ;Restore
> registers
> > > >         movwf   STATUS
> > > >         swapf   _w, f
> > > >         swapf   _w, w
> > > >         endm
> > > >
> > > > PAGE
> > > >
> > > >         org             0
> > > >         nop
> > > >
> > > >         goto    Main
> > > >
> > > >         org             4
> > > ;Interrupt
> > > >
> > > >         push
> > > >
> > > > Timer0
> > > >         btfss   INTCON, T0IF
> > > >                 goto    Iend
> > > >         movlw   165
> > > >         movwf   TMR0
> > > >         bcf             INTCON, T0IF
> > > >         incf    count
> > > >         movlw   200
> > > >         subwf   count, W
> > > >         btfss   STATUS, Z
> > > >                 goto    Step1
> > > >         movlw   0
> > > >         movwf   count
> > > > Step1
> > > >         movlw   0
> > > >         subwf   count, 0
> > > >         btfsc   STATUS, Z
> > > >                 bsf             PORTB, 3
> > > >         movf    pw1, W
> > > >         subwf   count, 0
> > > >         btfsc   STATUS, Z
> > > >                 bcf             PORTB, 3
> > > > Iend
> > > >
> > > >         pull
> > > >
> > > >         retfie
> > > >
> > > > Main
> > > >
> > > >         bsf             INTCON, GIE
> > > >         bsf             INTCON, T0IE
> > > >
> > > >         bsf     STATUS, RP0
> > > >         bcf             OPTION_REG, T0CS
> > > >         bsf             OPTION_REG, PSA
> > > >     bcf         STATUS,RP0          ; RAM PAGE
> 0
> > > >
> > > >         movlw   156
> > > >         movwf   TMR0
> > > >
> > > >         clrf    PORTB
> > > >
> > > >         bsf     STATUS, RP0
> > > >         bcf     TRISA ^ 0x080, 1
> > > >         bcf     TRISA ^ 0x080, 2
> > > >         clrf    TRISB
> > > >         bcf     STATUS, RP0
> > > >
> > > >         clrf    PORTA
> > > >         clrf    PORTB
> > > >         clrf    count
> > > >
> > > >         movlw   10
> > > >         movwf   pw1
> > > >
> > > > Loop
> > > >         nop
> > > > goto    Loop
> > > > end
> > > >
> > > >
>
=== message truncated ===


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