PicBasic Lookup command

[midali]

I have something strange with loockup command. I play with a RC transmitter...
If I turn on the pic with signal>185 then duty = 0 ; then I reduce the signal value under 185 , then duty=divf
If I move quickly the transmitter-stick (signal from 150 ) to maximum (200) I obtain random different values for duty, like 250 ,191, 90, 223 and sometime 255.
If I move slow the transmitter-stick , then duty = divf all time, so work perfectly.

Can somebody explain me whats happen here , please ? I'm very confused..!!

#CONFIG
    __config _CONFIG1, _FOSC_INTOSC & _MCLRE_OFF & _CP_ON & _CLKOUTEN_OFF
    __config _CONFIG2, _PLLEN_OFF & _LVP_OFF
#ENDCONFIG

DEFINE OSC 4
OSCCON = %01101000
@ ERRORLEVEL -306   ; turn off crossing page boundary message
include "lcd.bas"
ADCON0 = %00000000   
ADCON1 = %00000000     
CM1CON0 = 0   ' COMPARATORS OFF
CM1CON1 = 0
CM2CON0 = 0   ' COMPARATORS OFF
CM2CON1 = 0    
CPSCON0 = 0   'CAPACTIVE SENSE MODULE OFF
RCSTA.7 = 0   'SERIAL PORT OFF

OPTION_REG.7 = 1 'DISABLE PULL UP

TRISA  = %00000000
TRISB  = %00000000
TRISC  = %00000000

ANSELA = %00000000
ANSELB = %00000000

PORTA  = %00000000
PORTB  = %00000000
PORTC  = %00000000

WPUB   = %00000000 
LATC   = 0

divf   var byte : divf = 0
signal var byte
value  var byte : value =0
duty   var byte : duty = 0

gosub lcdrst:pause 300

main:
pulsin portb.0 , 1 , signal
if signal > 185 then signal = 185

if signal > 160 then
    value = (signal - 160) ' value max 25  
    lookup value ,[0,30,40,50,65,80,90,100,117,136,153,168,180_
                 ,191,201,209,217,223,233,237,241,244,247,250,255],divf                            	                     
else                 
    divf  = 0
    value = 00
endif
if duty <> divf then duty = divf
     
lcdout $fe, $80 , "Value = " , dec3 value
lcdout $fe, $C0 , "DUTY =  " , dec3 DUTY

goto main

'-------------------------- LCD ----------------------------- 
lcdrst:
lcdout, $fe, 1
pause 10
return

[HenrikOlsson]

If I turn on the pic with signal>185 then duty = 0 ; then I reduce the signal value under 185 , then duty=divf

The first value in the LOOKUP table is returned when value is 0. You have 25 entries in the table so value should range from 0 to 24. When signal is >185 value is 25 which points outside of the table in which case divf remains unchanged - so if this is at startup it remains at 0.

If I move quickly the transmitter-stick (signal from 150 ) to maximum (200) I obtain random different values for duty, like 250 ,191, 90, 223 and sometime 255.
If I move slow the transmitter-stick , then duty = divf all time, so work perfectly.

This I don't think has anything to do with the LOOKUP command. Have you looked at the actual pulses being measured by the PIC, is it possible that they actually ARE varying in widht (due to noise in the stick or whatever) and that the PIC is doing exactly as it should?

/Henrik.