本帖最后由 wulin 于 2021-9-7 08:36 編輯
最簡單的方法是用定時器，按需要的脈沖寬度和變化周期做一個數組，定時器中斷函數按序從數組中取值作重載值即可。示例如下：是一個按正弦規律變化的PWM波形。
- #include <reg51.h>
- sbit PWM=P1^0;
- unsigned char code K_Sine[256]={
- 0x00,0x01,0x03,0x04,0x06,0x07,0x09,0x0a,0x0c,0x0d,0x0f,0x10,
- 0x12,0x13,0x15,0x16,0x18,0x19,0x1b,0x1c,0x1e,0x1f,0x21,0x22,
- 0x24,0x25,0x27,0x28,0x2a,0x2b,0x2d,0x2e,0x2f,0x31,0x32,0x34,
- 0x35,0x36,0x38,0x39,0x3b,0x3c,0x3d,0x3f,0x40,0x41,0x43,0x44,
- 0x45,0x47,0x48,0x49,0x4a,0x4c,0x4d,0x4e,0x4f,0x50,0x52,0x53,
- 0x54,0x55,0x56,0x57,0x58,0x5a,0x5b,0x5c,0x5d,0x5e,0x5f,0x60,
- 0x61,0x62,0x63,0x64,0x65,0x66,0x67,0x67,0x68,0x69,0x6a,0x6b,
- 0x6c,0x6d,0x6d,0x6e,0x6f,0x70,0x70,0x71,0x72,0x72,0x73,0x74,
- 0x74,0x75,0x76,0x76,0x77,0x77,0x78,0x78,0x79,0x79,0x7a,0x7a,
- 0x7b,0x7b,0x7b,0x7c,0x7c,0x7d,0x7d,0x7d,0x7d,0x7e,0x7e,0x7e,
- 0x7e,0x7f,0x7f,0x7f,0x7f,0x7f,0x7f,0x7f,0x7f,0x7d,0x7b,0x7a,
- 0x78,0x77,0x75,0x74,0x72,0x71,0x6f,0x6e,0x6c,0x6b,0x69,0x68,
- 0x66,0x65,0x63,0x62,0x60,0x5f,0x5d,0x5c,0x5a,0x59,0x57,0x56,
- 0x54,0x53,0x51,0x50,0x4f,0x4d,0x4c,0x4a,0x49,0x48,0x46,0x45,
- 0x43,0x42,0x41,0x3f,0x3e,0x3d,0x3b,0x3a,0x39,0x37,0x36,0x35,
- 0x34,0x32,0x31,0x30,0x2f,0x2e,0x2c,0x2b,0x2a,0x29,0x28,0x27,
- 0x26,0x24,0x23,0x22,0x21,0x20,0x1f,0x1e,0x1d,0x1c,0x1b,0x1a,
- 0x19,0x18,0x17,0x17,0x16,0x15,0x14,0x13,0x12,0x11,0x11,0x10,
- 0x0f,0x0e,0x0d,0x0c,0x0c,0x0b,0x0a,0x0a,0x09,0x09,0x08,0x08,
- 0x07,0x07,0x05,0x05,0x04,0x04,0x04,0x03,0x03,0x03,0x02,0x02,
- 0x02,0x02,0x02,0x01,0x01,0x01,0x01,0x01,0x00,0x00,0x00,0x00,
- 0x00,0x00,0x00,0x00}; //kindred sine wave
- void InitTimer0(void)
- {
- TMOD = 0x01;
- TH0 = 0xff;
- TL0 = 0x00;
- EA = 1;
- ET0 = 1;
- TR0 = 1;
- }
- void main(void)
- {
- InitTimer0();
- while(1);
- }
- void Timer0Interrupt(void) interrupt 1
- {
- static unsigned char i;
- PWM=~PWM;
- TH0 = 0xff;
- TL0 = K_Sine[i];
- i++;
- }
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