Speed regulator for sewing machine

[Kenwood]

Thanks again for your ideas. I increased the encoder resolution to about 2500 pluses per inch of travel and counted the pulses. I seems to work quite well with good low speed movement. My sewing machine drive is a servo so I need to feed it with a frequency. I feed the PWM output to a filter and then to an ADC ( AD654) chip to give me 0 to 15kHz out.

'****************************************************************
'*  Name    : Pulse Count.BAS                                      *
'*  Author  : Jan                                      *
'*  Notice  : Copyright (c) 2013 [select VIEW...EDITOR OPTIONS] *
'*          : All Rights Reserved                               *
'*  Date    : 27/12/2013                                        *
'*  Version : 1.0                                               *
'*  Notes   : Count pulses in                                                  *
'*          : 16F88                                                  *
'****************************************************************

Include "modedefs.bas"          ' Include serial modes
define OSC 20

#CONFIG __config _CONFIG1, _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF & _CCPMX_RB3 & _CCP1_RB3 
#ENDCONFIG    'Configure CCP1 (RB3) to PWM out


SO      VAR PORTB.5     'Define serial out pin
P1      var PORTA.0     'Define input pin  X
P2      VAR PORTA.1     'Define input pin  Y
W1      var WORD 
W2      VAR WORD
W3      VAR WORD
led     var PORTB.0
TRISA = %11111111
ANSEL = %00000000
output   led               
low      led               'set led off

 displayloop:

        count  P1,10,W1
        COUNT  P2,10,W2 
        W3 = (W1 HYP W2)               'HYPOTENUSE CALCULATION 
        if W3 > 120 THEN               'Turn on lrd if Hypot is over 
        HIGH LED                       'Turn on led on RB0
        ENDIF
        'if W3 < 100 then
        'low led
        'endif  
        
        Serout SO,N2400,[#W3]

disp:   Serout SO,N2400,[" Pulses",13,10]        ' Display trailer
        hpwm 1,W3,2000

                          
        Goto DISPLAYLOOP                 ' Forever

Now I am trying to improve the design and I was told to try changing the PWM to a 50% duty cycle and very the frequency (hpwm 1,127,W5). This idea gives me my 15K but the lowest I can get is about 1.5KHz and I really need close to 0.
I am trying to come up with a scheme that will use Timer 0 quickly sample the PWM output and replicate the output with a 1,500 hz offset. Any ideas would be appreciated.

'****************************************************************
'*  Name    : Pulse Count.BAS                                      *
'*  Author  : Jan                                      *
'*  Notice  : Copyright (c) 2013 [select VIEW...EDITOR OPTIONS] *
'*          : All Rights Reserved                               *
'*  Date    : 27/12/2013                                        *
'*  Version : 1.0                                               *
'*  Notes   : Count pulses in                                                  *
'*          : 16F88                                                  *
'****************************************************************

Include "modedefs.bas"          ' Include serial modes
define OSC 20

#CONFIG __config _CONFIG1, _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF & _CCPMX_RB3 & _CCP1_RB3 
#ENDCONFIG    'Configure CCP1 (RB3) to PWM out


SO      VAR PORTB.5     'Define serial out pin
P1      var PORTA.0     'Define input pin  X
P2      VAR PORTA.1     'Define input pin  Y

W1      var WORD 
W2      VAR WORD
W3      VAR WORD
W4      var word
W5      var word

led     var PORTB.0       

TRISA = %11111111
ANSEL = %00000000
output   led               
low      led               'set led off

 displayloop:

        count  P1,10,W1
        COUNT  P2,10,W2
      
        W3 = (W1 HYP W2)               'HYPOTENUSE CALCULATION 
        if W3 > 120 THEN               'Turn on lrd if Hypot is over 
        HIGH LED                       'Turn on led on RB0
        ENDIF
        W4 = (W3 + 20)                 'Add 20 to overcome min pwm frequence
        W5 = (W4 * 100)                'Times 100 to give min of 2 kHz
        Serout SO,N2400,[#W5]

disp:   Serout SO,N2400,[" Pulses",13,10]        ' Display trailer
        hpwm 1,127,W5
      
                          
        Goto DISPLAYLOOP                 ' Forever

Thanks Jan