pwm code translation

[Aaron]

pls i need help in translating this code from C into gcb so i can complete a project, the chip involved is PIC16F684....THE CODE is for a pure sine wave inverter..this is the code..

unsigned char sin_table[32]={0,25,49,73,96,118,137,
159,177,193,208,220,231,239,245,249,250,249,245,
239,231,220,208,193,177,159,137,118,96,73,49,25};

unsigned int TBL_POINTER_NEW, TBL_POINTER_OLD, TBL_POINTER_SHIFT, SET_FREQ;
unsigned int TBL_temp;
unsigned char DUTY_CYCLE;

void interrupt(){
if (TMR2IF_bit == 1){
TBL_POINTER_NEW = TBL_POINTER_OLD + SET_FREQ;
if (TBL_POINTER_NEW < TBL_POINTER_OLD){
CCP1CON.P1M1 = ~CCP1CON.P1M1; //Reverse direction of full-bridge
}
TBL_POINTER_SHIFT = TBL_POINTER_NEW >> 11;
DUTY_CYCLE = TBL_POINTER_SHIFT;
CCPR1L = sin_table[DUTY_CYCLE];
TBL_POINTER_OLD = TBL_POINTER_NEW;
TMR2IF_bit = 0;
}
}

void main() {
SET_FREQ = 410;
TBL_POINTER_SHIFT = 0;
TBL_POINTER_NEW = 0;
TBL_POINTER_OLD = 0;
DUTY_CYCLE = 0;
ANSEL = 0; //Disable ADC
CMCON0 = 7; //Disable Comparator
PR2 = 249;
TRISC = 0x3F;
CCP1CON = 0x4C;
TMR2IF_bit = 0;
T2CON = 4; //TMR2 on, prescaler and postscaler 1:1
while (TMR2IF_bit == 0);
TMR2IF_bit = 0;
TRISC = 0;
TMR2IE_bit = 1;
GIE_bit = 1;
PEIE_bit = 1;

 while(1);

}

[Anobium]

Please send vasts amount of money to my eBay account. I cannot test but this should work.

You do not not all the complexity of the source with Great Cow BASIC.

; ----- Configuration
  #chip 16F684,8

    Dim TBL_POINTER_NEW, TBL_POINTER_OLD, TBL_POINTER_SHIFT, SET_FREQ as Integer


    SET_FREQ = 410
    TBL_POINTER_SHIFT = 0
    TBL_POINTER_NEW = 0
    TBL_POINTER_OLD = 0
    DUTY_CYCLE = 0


    Dir portc.2 out
    HPWM 1, SET_FREQ, DUTY_CYCLE
    On Interrupt Timer2Match call HandleSineWave


    Do

    Loop

    Sub HandleSineWave

        TBL_POINTER_NEW = TBL_POINTER_OLD + SET_FREQ
        if (TBL_POINTER_NEW < TBL_POINTER_OLD) then
            P1M1 = !P1M1 ' Reverse direction of full-bridge
        End if

        TBL_POINTER_SHIFT =  FnLSR(TBL_POINTER_NEW, 11)
        DUTY_CYCLE = TBL_POINTER_SHIFT

        readtable sin_table, DUTY_CYCLE,  CCPR1L

        TBL_POINTER_OLD = TBL_POINTER_NEW
        TMR2IF = 0

    End Sub

    table sin_table
    0,25,49,73,96,118,137,
    159,177,193,208,220,231,239,245,249,250,249,245,
    239,231,220,208,193,177,159,137,118,96,73,49,25
    end table

[Anobium]

To my amazement - I just hooked up an 18f with the same code and I get.... PWM and the frequency is changing.

[Aaron]

Anobium you are the boss, with this i can now finish my project, thank alot

[Aaron]

pls while making use of the interupt i do not understand the timer2match

[Anobium]

From your source the Interrupt was checking TMR2IF ad the source was setting TMR2IE_bit. These relate to Timer2Match,

So, we call Timer2Match enabling TMR2IE and we need to clear,TMR2IF

I may be incorrect but this still looks ok today.

[William Roth]

HPWM uses uses timer 2 as a clock source. Timer2 has a timer register (TMR2) and a period register (PR2) . TMR2 increments until its value "matches" the value in the PR2 register. At that time the TMR2IF flag bit is set and, if enabled, an interrupt is triggered and TMR2 reset to zero, The time between interrupts is the "period". To change the period, you can change the value of the PR2 Register.

The default value of the PR2 register is 255, So after 255 ticks TMR2 "matches" PR2 and "overlows" to zero and starts over. If the PR2 register is loaded with a value of 127, then TMR2 will increment unitil it reaches a value of 127 (matches PR2) and then reset to zero. This will divide the period by 2, thus doubling the frequency,