BugWorkShop - 甲蟲工作室: DIY - PIC：PIC18F4550 PWM 正弦波程式 (六十一)

DIY - PIC：PIC18F4550 PWM 正弦波程式 (六十一)：

Microchip PIC18F4550 PWM可調整佔空比變成正弦波程式，程式主要利用預先設定的一系統的數值，產生一連串的PWM及不同的佔空比值訊號，然後通過低通濾波器 (LPF) 的電子線路，輸出組合一連串的PWM的訊號，便會變成正弦波。

▲ PWM正弦波程式流程圖

程式：

const rom char waveform[64] = {
127, 139, 152, 164, 176, 187, 198, 208,
217, 225, 233, 239, 244, 249, 252, 253,
254, 253, 252, 249, 244, 239, 233, 225,
217, 208, 198, 187, 176, 164, 152, 139,
127, 115, 102, 90, 78, 67, 56, 46,
37, 29, 21, 15, 10,   5,   2,   1,
0,   1,   2,   5, 10, 15, 21, 29,
37, 46, 56, 67, 78, 90, 102, 115}; // Sinewave lookup-table

void main(void)
{

    //                1234567890123456
    char LCD_name[] ="BWS PWM->SINE v1";
    char LCD_name2[]="                ";

    ADCON0 = 0x00;             // Disable the AD converter
    ADCON1 = 0x0F;             // Set all ports to digital
    TRISB = 0b11100000;     // Set PORTB RB5 as Key In
    TRISC = 0b11111001;     // Set PORTC C1 and C2 as PWM output
    LATC   = 0b00000000;     // Clear PORTC

    // Initialise LCD
    OpenXLCD(FOUR_BIT&LINES_5X7);    // Init the LCD Display
    while(BusyXLCD());
    WriteCmdXLCD(BLINK_OFF & CURSOR_OFF );
    while(BusyXLCD());
    stdout = _H_USER;        // Redirect I/O to LCD
    LcdSetLine1();                        // Put cursor on start of line 1
    putsXLCD(LCD_name);         // Display text

    //Configure CCP module as (PR2+1)*4*TOSC*T2_PS
    PR2     = 0b10011011;       // PWM Frequency = 152 = 2KHz = 0.5ms
    T2CON   = 0b00000100 ;      // 11=1:16 00=1:1
    CCP1CON = 0b00001100 ; // PWM Mode P1A/P1C/P1B/P1D=H <5:4> DC
    CCP2CON = 0b00111100 ; // PWM Mode P2A/P2C/P2B/P2D=H
                                                   // Duty Cycle CCP1CON<5:4>+CCPR1L

    RCONbits.IPEN   = 0;     // Interrupt Priority Control: OFF
                                            // (RCON register IPEN bit = 0)
    PIE1bits.TMR2IE = 1;     // Timer2 interrupt enable
    INTCONbits.PEIE = 1; // peripheral interrupt enable
    // INTCON register bit b6: low interrupt enable / disable
    // (When interrupt priority control)
    INTCONbits.GIE = 1;    // all interrupt enable
    // INTCON register bit b7: high interrupt enable / disable
    // (When interrupt priority control)

    while(1)
    {

    } // End While
}

void high_isr (void)
{
    PIR1bits.TMR2IF = 0;    // Timer2 interrupt flag to 0
    CCPR1L = waveform[wave];
    CCPR2L = waveform[wave];
    wave++;
    if (wave > 64) wave=0;
}