Simple Servo Position Control Program - Is this right?

[Acetronics2]

Hi, Marcus

this one should work as desired ...

'****************************************************************
'*  Name    : GrassBurner.BAS                                   *
'*  Author  : Acetronics                                        *
'*  Notice  : Copyright (c) 2010                              *
'*          : All Rights Reserved                               *
'*  Date    : 23/12/2010                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************
'
@ __config _CONFIG1, _INTRC_IO & _WDT_ON & _LVP_OFF & _CP_OFF
' DEFINES
Define OSC 8
Define BUTTON_PAUSE 0
' Internal Osc 8Mhz
OSCCON = %01110010
' Turn off A/D conversion - Digital Inputs
ADCON0 = 0
ANSEL = 0
' Comparators Off
CMCON  = 7
 
'Define variables and pins
I         VAR BYTE
Position var WORD
Delay  var Byte
OldButton  var bit
PORTA  = 0
TRISA   = %11111101
BUTTON_  VAR PORTA.0
SERVO  VAR PORTA.1
 
buttonloop:     ' Button check loop
 OldButton = 0
 LOW Servo
 Pulsout SERVO, 300  ' pulse to place servo to neutral
 Pause 19
 
BUTTON BUTTON_,1,255,0,Delay,0,Buttonloop
 OldButton = 1       ' Launched ... We've pressed it !!!
'******************************************************************************
positionloop:  'Servo position control loop
 
I = 0       ' Reset time counter
While ( OldButton  AND ( I < 75 ))   '  if button has been pushed and time < 1.5s
 
 IF I >= 50 THEN     ' 1 second is ... 50 x 20 ms !    
  position = 300
 ELSE 
  POSITION = 200
 ENDIF 
 
 LOW Servo
 Pulsout SERVO, Position  ' pulse to servo 
 
 PAUSEUs 19813 - ( Position * 5 )        ' time between pulses
 
 I = I+1                         'Increase Time counter
Wend                                ' go for seeking a new button push ...
 
goto buttonloop
End         'end of program supposed never reached

may be you'll have to modify a bit the " @ __config ......" line if you use PM as an assembler.

Also correct " IF I >= 50 ..." to i.e. " IF I >= 55 " to take servo positionning time into account ... knowing 1 unit is 20 ms.

Alain