DIY - PIC：PIC18F4550 PWM 控制 LED 光暗程式 (五十四)

DIY - PIC：PIC18F4550 PWM 控制 LED 光暗程式 (五十四)：

程式的概念是利用改變 PWM (Pulse Width Modulation) 時間佔空比  (Duty Cycle)，便可改變供電電壓值到 LED，達到調節 LED 的光暗。程式會由光慢慢地變暗，然後再從暗慢慢地發光，循環這變化。

▲ PIC18F4550 PWM控制LED光暗程式流程圖

主程式：

void main(void) {     //                1234567890123456                    char LCD_name[] ="BWS PWM - RC1 V1";     char LCD_name2[]="                ";     unsigned char dc;                   // Duty Cycle     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   = 0b00000111 ;    // 1:16     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         while(1)     {         // PWM resolution is 10 bits don't use last 2 less significant bits CCPxCON,         // so only CCPRxL have to be touched to change duty cycle            for(dc = 0 ; dc < 128 ; dc++){                     CCPR1L = dc ;                     CCPR2L = 128 - dc ;                     LcdSetLine2();        // Put cursor on start of line 2                     printf("Duty Cycle=%04i", CCPR2L);                     }                       for(dc = 127 ; dc > 0 ; dc--){                     CCPR1L = dc ;                     CCPR2L = 128 - dc ;                     LcdSetLine2();       // Put cursor on start of line 2                     printf("Duty Cycle=%04i", CCPR2L);                     }     } // End While }

▲ LED 會自動慢慢變亮或慢慢變暗

▲ Duty Cycle 會自動增加或減少

2011 年 04 月 09 日 天氣報告

氣溫：21.9 度 @ 23:00 

相對濕度：百分之85%  

天氣：天色大致良好