Hardware PWM Code Optimisation

About Hardware PWM Code Optimisation

For compatibility all channels are supported by default. This is maintains backward compatibility.

To mimise the code, use the following to disable support for a specific Capture/Compare/PWM (CCP) module, timers or the PWM module.

Setting a constant to FALSE will remove the support of the capability from the method and therefore will reduce the program size. 

    #define USE_HPWMCCP1 FALSE
    #define USE_HPWMCCP2 FALSE
    #define USE_HPWMCCP3 FALSE
    #define USE_HPWMCCP4 FALSE

To further mimise the code, use the following to disable support for a specific PWM channels. Only PWM channels 5, 6 and 7 are supported. 

    #define USE_HPWM3 FALSE
    #define USE_HPWM4 FALSE
    #define USE_HPWM5 FALSE
    #define USE_HPWM6 FALSE
    #define USE_HPWM7 FALSE

To further mimise the code, use the following to disable support for a specific timers.

    #define USE_HPWM_TIMER2 TRUE
    #define USE_HPWM_TIMER4 TRUE
    #define USE_HPWM_TIMER6 TRUE

Example

This will save 335 bytes of program memory by removing support for CCP1, CCP2 and CCP4.

    #chip 16f18855,32
    #Config MCLRE_ON

    UNLOCKPPS
        RC2PPS = 0x0A       'RC2->CCP2:CCP2;
    LOCKPPS

    #define USE_HPWMCCP1 FALSE       ' This is not used so optimise          ' <<< the constants that select which CCP channels get compiled in
    #define USE_HPWMCCP2 TRUE        ' This is used so include in the compiled code
    #define USE_HPWMCCP3 FALSE       ' This is not used so optimise
    #define USE_HPWMCCP4 FALSE       ' This is not used so optimise


    'Setting the port an output is VERY important... LED will not work if you do not set as an output.
    dir portC.2 out    ; CCP2

    do forever
            For Bright = 1 to 255
                HPWM 2, 40, Bright
                wait 10 ms
            next

    loop

Key line: #define USE_HPWMCCP1 FALSE (and the matching lines for CCP3 and CCP4) — since only channel 2 is used by the HPWM 2, 40, Bright call below, disabling the other three channels' compiled-in support saves 335 bytes of program memory without changing behaviour.

See Also:

  • HPWM CCP — the command whose channel support this page’s constants control
  • HPWM 10 Bit — the 10-bit PWM module, which has its own USE_HPWMn constants
  • HPWM 16 Bit — the 16-bit PWM module, which has its own USE_HPWM16_n constants
Prev  Up  Next
  Home