Sub HPWM(channel As uByte,freq As uInteger,duty_cycle As uInteger,Output_Config As uByte,Output_polarity As uByte)

Dim period As uShort, ps As uInteger, CCP As uShort

' Hardware PWM module 
' Larry Bradley, November 26, 2003


' "Channel" is the desired CCP channel (1 or 2)
'
' "Freq" is the frequency in hertz desired for the output. Note that there
' are miniumum frequencies that can be used, depending on the oscillator
' frequency being used. Check the data sheets.
' For example, at 20 mHz, the min freq is 1221 Hz
'
' "duty_cycle" specifies the on/off ratio of the output waveform
' It ranges from 0 to 1023, the on fraction being "duty_cycle/1024"
' 
' The following are only used on PICs with the enhanced PWM module. Check
' the PIC documentation for details.
' "Output_config" is 0,1,2,3: single-ended, full-brigde forward, half_bridge, full-bridge reverse
'
' "Output_polarity" is 0,1,2,3: 0 is active high for the single-ended output, 2 is active low 
'
' Requires the following #DEFINE statements, either in the 18Fxxxx.BAS file
' or in the user's code:
'
'#DEFINE CCP_CHANNELS [1|2]

' Compute the prescaler value 

	duty_cycle = duty_cycle And 0x3FF	' Restrict to < 1024
	movlw	LOW (( FOSC ) / 1024)
	movwf	ps
	movlw   (( FOSC ) / 1024) >> 8
	movwf   ps+1
	ps = ps/freq
	
 
    ' Set up period
    movlw   LOW (( FOSC ) / 4)
    movwf   period
    movlw   LOW ((( FOSC ) / 4) >> 8)
    movwf   period+1
    movlw   (( FOSC ) / 4) >> 16
    movwf   period+2
  
  
  	' Set up Timer 2 prescale value 
	' Assume ps = 0, thus 1:1
	T2CKPS0 = 0  : T2CKPS1 = 0
	If ps > 0 Then
		' 1:4 or 1:16
		T2CKPS0 = 1
		period = Shr(period,2)	'pr2 = pr2/4
		If ps > 4 Then
			' 1:16
			T2CKPS1 = 1
			period = Shr(period,2)	'pr2 = pr2/16
		End If
	End If
  	
  	' Set up CCP PR register
    PR2 = period / freq - 1
    
    ' The PR register will have a value from 0 to 255 - this is
    ' the period of the output waveform
    ' We specify duty cycle as the fraction of the period that
    ' the waveform is ON, the fraction being (0 to 1023)/1024
    
    ccp = (PR2+1)
    ccp = ccp * duty_cycle
    ' We have an 18 bit result in a 24 bit field, and we only want the high order 10 bits
    ' of those 18
    ' 0b 0000 00nn nnnn nnnn xxxx xxxx
    ' Shift right by 2 bits gets  
    ' 0b 0000 000 nnnn nnnn nnxx xxxx
    ' Put the middle byte into the CCPRxL register (most sign. 8 bits)
    ' and the next 2 bits into the CCPxCON register
    ccp = Shr(ccp,2)
    
    '#If CCP_CHANNELS <> 2
    #ifndef CCP2CON
    ' Only one channel
   	' Set output config and polarity
    CCP1CON = 0x0C		' Set CCP module into PWM mode
   	P1M1 = Output_config.1
   	P1M0 = Output_config.0
   	CCP1M1 = Output_polarity.1
   	CCP1M0 = Output_polarity.0
    
    CCPR1L = ccp.Byte1		' Set duty cycle high 8 bits
    ' Set duty cycle low 2 bits
    DC1B1 = ccp.7
   	DC1B0 = ccp.6
    #else
    
    If channel = 1 Then
    	CCP1CON = 0x0C		' Set CCP module into PWM mode
    	CCPR1L = ccp.Byte1		' Set duty cycle high 8 bits
    	' Set duty cycle low 2 bits
    	DC1B1 = ccp.7
    	DC1B0 = ccp.6
    	' Set output config and polarity
    	P1M1 = Output_config.1
    	P1M0 = Output_config.0
    	CCP1M1 = Output_polarity.1
    	CCP1M0 = Output_polarity.0
    End If
    
 	If channel = 2 Then
	 	CCP2CON = 0x0C			' Set CCP module into PWM mode
    	CCPR2L = ccp.Byte1		' Set duty cycle high 8 bits
    	' Set duty cycle low 2 bits
    	DC2B1 = ccp.7
    	DC2B0 = ccp.6
    	' Set output config and polarity
    	P2M1 = Output_config.1
    	P2M0 = Output_config.0
    	CCP2M1 = Output_polarity.1
    	CCP2M0 = Output_polarity.0
   	End If
    
    #endif
    ' Turn on timer 2
    TMR2ON = 1
    
    
' For testing ...
'   Dim s(12) As String
'    putcrlf()
'    
'    str(duty_cycle,s)
'    puts(s)
'    putc(" ")
'    
'    strhex(pr2,s)
'    puts(s)
'    putc(" ")
'    
'    strhex(ccp,s)
'    puts(s)
'    putc(" ")
'     
'     Dim x As uInteger
'     x = Shr(ccp,6)	
'    str(x,s)
'    puts(s)
    
End Sub