contorlling servo motor

[HenrikOlsson]

Hi,
IIRC the resolution of the pulsout command is 10uS no matter what osciallator frequency you are using -as long as you let PBP know what frequency you are using.

So if you tell PBP that you are using a 10Mhz clock but in reallity it's 20MHz you'll get 6.5ms instead of 13 with Pulsout 0,130. Just remeber that all timing sensetive commands, like Pause, Serin/out, Pulsin etc also is affacted the same way.

/Henrik.

[Acetronics2]

Hi, Henrik

No,NO ...PULSOUT is one of the XTAL freq dependant commands ... There's NO DEFINE to get rid of that !!!

@ 20Mhz, the result will simply be 20/4 times that @ 4Mhz ...

Alain

[HenrikOlsson]

Alain,
Yep, you're right! I didn't remeber correctly..... :-(

To quote the docs:

If a 4MHz oscillator is used, the Period of the generated pulse will be in 10us increments. If a 20MHz oscillator is used, Period will have a 2us resolution. Defining an OSC value has no effect on PULSOUT. The resolution always changes with the actual oscillator speed.

Sorry for the confusion!

/Henrik.

[shirleyz]

so do u all mean this:

When a 20MHz crystal is used, the time
interval of PULSOUT is in units of 2us. For example, the following PicBasic statement generates a pulse with a width of 1.3 ms from bit 0 of PortB (1.3 ms = 1300us and 1300/2 = 650):
PULSOUT 0, 650

izzit like that?? can u all give sample codes, so i can see clearly..
thanks

[Acetronics2]

Hi, Shirleyzzzzzzzz ...

that's it !

Find here an application ...

'****************************************************************
'*  Name    : Glow Driver with Fail Safe - 1                    *
'*  Author  : Ironsides                                         *
'*  Notice  : Copyright (c) 2004 C                              *
'*          : All Rights Reserved                               *
'*  Date    : 24 Feb 2004                                       *
'*  Version : 1.0                                               *
'*  Notes   : Turns on glow driver to glow plug at low throttle *
'*            If sigal is lost for 5 secs, engine is killed and *
'*            glow power turned off                             *
'*          ; An N Channel MOSFET is needed to carry the current*
'*          ; See the circuit diagram for details               *
'*  Caution : Should have a safety cut off switch in the pits   *
'*          : For PIC 12F675                                    *
'****************************************************************

;The 12F675 has both analog converters and analog comparators.  
;You must disable both to use the I/O pins for digital functions.  
;In addition, the register that controls the analog converters 
;has been named ANSEL, and it has a different format that the ADCON1 
;register found on most PICmicro MCUs
PCON.3 = 1
ANSEL = 0               ;needed as as above
CMCON = 7
ASM
      errorlevel  -302  ; Suppress message 302
      bcf   STATUS,RP0  ; Bank 0
      clrf  GPIO        ; Init GPIO
      movlw 07h         ; Set GP<2:0> to
      movwf CMCON       ;   digital IO
      bsf   STATUS,RP0  ; Bank 1
      clrf  ANSEL       ; Digital IO
      movlw 0Ch         ; Set GP<3:2> as inputs
      movwf TRISIO      ; and set up GP<5:4,1:0> as outputs
endasm

DEFINE OSC4             ;sets up 4 meg internal oscillator
THROTTLE VAR GPIO.1     ;Outputs to throttle servo                    - Pin 6
GLOW     VAR GPIO.2     ;Output to MOSFET driving glow driver         - Pin 5
RADIO    VAR GPIO.3     ;Input from receiver                          - Pin 4

TEST     VAR WORD       ; Used to test for loss of signal
P        VAR WORD       ; This stores the PULSIN value    
N        VAR WORD       ; Loop counter        
;*********************************************************************
TEST = 0
RX:                     ; This is where we wait for a signal from the Tx                         
PULSIN RADIO,1,P        ; With 4 meg oscillator, PULSIN measures at 10 millisecs
IF (P < 50) and (test = 0) then GOsub LOS ; Loss of signal 
PULSIN RADIO,1,P        ; Check to see if signal re-established
if (P < 50) and (test = 1) then goto kill_glow
                        ; There is loss of signal - kill the engine
IF (P > 100)  and (P < 130) THEN GOSUB SW_ON       ; Turn on glow
IF (P > 130)                THEN GOSUB SW_OFF      ; Turn off glow

goto RX    
;********************************************************************

SW_ON:
    HIGH GLOW                 ; This tunrs on the glow signal on Pin 5
    PULSOUT THROTTLE, p       ; send the normal signal to the throttle servo
    RETURN

SW_OFF:
    LOW GLOW                  ; This turns off the glow signal on Pin 5
    PULSOUT THROTTLE, p       ; send the normal signal to the throttle servo
    RETURN

LOS:    
     TEST = 1                 ; Set for loss of signal
     For N = 1 to 5
     Pause 1000               ; one second  - 5 secs total
     NEXT n
     return

KILL_GLOW:
     low glow               ; Turn off the glow plug 
     
KILL_ENGINE:
     PULSOUT throttle, 101  ; Kill engine  - adjust this value to get the 
                            ; carb closed to prevent dirt from entering
     pause 50               ; Needs a pause to stop servo hum
     goto KILL_ENGINE       ; Keep in loop to stop spurious signals

;********************************************************************

END                         ;Terminate the program

Alain

[shirleyz]

so the code that i write, izzit correct....i mean pulseout code for 20MHz???

[Acetronics2]

Hi, Shirleyzzzzzzzz ...

that's it !

Alain