如果LED閃爍（玩轉單片機之智能車小露——LED閃爍實戰）不能滿足你，那么七彩LED呼吸燈絕對可以給你帶來足夠的樂趣。
七彩LED呼吸燈一般都需要PWM進行調光，所以編程有無限的靈活性。本文七彩呼吸燈可以實現彩虹單色顯示、RGB任意顏色顯示、單色亮度呼吸、七彩顏色轉換呼吸：

//呼吸燈模式：關閉呼吸、單色呼吸、七彩轉換呼吸
#define	BLED_MODE_OFF			0X00
#define	BLED_MODE_SINGLE		0X01
#define	BLED_MODE_COLOR			0X02

//顏色：關閉及RGB組合彩虹顏色
#define	BLED_COLOR_OFF			0X00
#define	BLED_COLOR_RED			0X01
#define	BLED_COLOR_ORANGE		0X02
#define	BLED_COLOR_YELLOW		0X03
#define	BLED_COLOR_GREEN		0X04
#define	BLED_COLOR_CYAN			0X05
#define	BLED_COLOR_BLUE			0X06
#define	BLED_COLOR_PURPLE		0X07
#define	BLED_COLOR_WHITE		0X08

//亮度：0x0100~0x1000;
#define BLED_BRIGHT				0x0fff

void BLEDTurnOn(unsigned char color);
void BLEDDisplayColor(unsigned char red,unsigned char green,unsigned char blue);
void BLEDBreath(unsigned char mode,unsigned char color);
void BLEDTurnOff(void);

STC32G單片機PWM初始化

控制七彩LED前先要初始化PWM（GPIO設置、PWM設置、端口切換）：

void BLEDInit(void){
	GPIO_InitTypeDef gpio;
	PWMx_InitDefine pwm;
	
	gpio.Mode = GPIO_OUT_PP;
	gpio.Pin = GPIO_Pin_LOW;
	
	GPIO_Inilize(GPIO_P2,&gpio);

	pwm.PWM_Mode = CCMRn_PWM_MODE1;
	pwm.PWM_Duty = 0x0000;
	pwm.PWM_EnoSelect = ENO5P;
	PWM_Configuration(PWM5, &pwm);
	
	pwm.PWM_EnoSelect = ENO6P;
	PWM_Configuration(PWM6, &pwm);
	
	pwm.PWM_EnoSelect = ENO7P;
	PWM_Configuration(PWM7, &pwm);
	
	pwm.PWM_Period = 0x1000; 
	pwm.PWM_DeadTime = 0;
	pwm.PWM_MainOutEnable= ENABLE;
	pwm.PWM_CEN_Enable   = ENABLE; 
	PWM_Configuration(PWMB, &pwm);
	
	PWM5_SW(PWM5_SW_P20);
	PWM6_SW(PWM6_SW_P21);
	PWM7_SW(PWM7_SW_P22);
	
	NVIC_PWM_Init(PWMB,DISABLE,Priority_0);
}

彩虹單色顯示

為簡化代碼，彩虹顏色的顯示使用二維數組記錄RGB占空比，通過color參數直接定位到ColorRaw數組中對應顏色的占空比。

unsigned char BLEDBreathMode;
unsigned char BLEDColor;
unsigned int BLEDScanCycle;

unsigned int code ColorRaw[9][3] = {
	{0x0000,0x0000,0x0000},					//OFF
	{BLED_BRIGHT,0x0000,0x0000},			//RED
	{BLED_BRIGHT,BLED_BRIGHT >> 2,0x0000},	//ORANGE
	{BLED_BRIGHT,BLED_BRIGHT,0x0000},		//YELLOW
	{0x0000,BLED_BRIGHT,0x0000},			//GREEN
	{0x0000,BLED_BRIGHT,BLED_BRIGHT},		//CYAN
	{0x0000,0x0000,BLED_BRIGHT},			//BLUE
	{BLED_BRIGHT,0x0000,BLED_BRIGHT},		//PURPLE
	{BLED_BRIGHT,BLED_BRIGHT,BLED_BRIGHT}};	//WHITE
	
void BLEDTurnOn(unsigned char color){
	unsigned int *pDuty;
	
	BLEDColor = color;
	BLEDBreathMode = BLED_MODE_OFF;
	pDuty = ColorRaw[color];

	PWMB_Duty5(pDuty[0]);
	PWMB_Duty6(pDuty[1]);
	PWMB_Duty7(pDuty[2]);
}

RGB任意顏色顯示

RGB任意顏色顯示也很簡單，將RGB顏色三個分量參數（0x00~0xFF）縮放到占空比量程后直接輸出：

void BLEDDisplayColor(unsigned char red,unsigned char green,unsigned char blue){
	BLEDBreathMode = BLED_MODE_OFF;
	
	PWMB_Duty5((unsigned int)red << 4);
	PWMB_Duty6((unsigned int)green << 4);
	PWMB_Duty7((unsigned int)blue << 4);
}

單色亮度呼吸和七彩顏色轉換呼吸

呼吸思路仍然是在定時中斷中按呼吸相應的呼吸規律更新RGB三種顏色的PWM占空比。
單色亮度呼吸熄滅效果不佳所以呼吸周期內只降低到最低亮度（0x0100）不會全熄。
七彩顏色轉換呼吸按紅->黃->綠->青->藍->紫->紅...依次循環轉換。

void BLEDBreath(uint8 mode,uint8 color){
	BLEDColor = color;
	BLEDBreathMode = mode;
	BLEDScanCycle = 0;
}

//Systick callback(20ms)
void SystickCallbackBLED(void){
	unsigned int *pDuty;
	
	if(BLEDBreathMode == BLED_MODE_SINGLE){			//單色亮度呼吸
		pDuty = ColorRaw[BLEDColor];
		
		if(++BLEDScanCycle > 128)
			BLEDScanCycle = 0;
		if(BLEDScanCycle < 64){
			PWMB_Duty5(pDuty[0] - min(pDuty[0],(((BLED_BRIGHT - 0x0100) >> 6) * BLEDScanCycle)));
			PWMB_Duty6(pDuty[1] - min(pDuty[1],(((BLED_BRIGHT - 0x0100) >> 6) * BLEDScanCycle)));
			PWMB_Duty7(pDuty[2] - min(pDuty[2],(((BLED_BRIGHT - 0x0100) >> 6) * BLEDScanCycle)));
		}
		else{
			PWMB_Duty5(pDuty[0] - min(pDuty[0],(((BLED_BRIGHT - 0x0100) >> 6) * (128 - BLEDScanCycle))));
			PWMB_Duty6(pDuty[1] - min(pDuty[1],(((BLED_BRIGHT - 0x0100) >> 6) * (128 - BLEDScanCycle))));
			PWMB_Duty7(pDuty[2] - min(pDuty[2],(((BLED_BRIGHT - 0x0100) >> 6) * (128 - BLEDScanCycle))));
		}
	}
	else if(BLEDBreathMode == BLED_MODE_COLOR){		//七彩顏色轉換呼吸
		if(++BLEDScanCycle > 448)
			BLEDScanCycle = 0;
		if(BLEDScanCycle < 64){
			PWMB_Duty5(BLED_BRIGHT);
			PWMB_Duty6((BLED_BRIGHT >> 6) * BLEDScanCycle);
			PWMB_Duty7(0x0000);
		}
		else if(BLEDScanCycle < 128){
			PWMB_Duty5(BLED_BRIGHT - (BLED_BRIGHT >> 6) * (BLEDScanCycle-64));
			PWMB_Duty6(BLED_BRIGHT);
			PWMB_Duty7(0x0000);
		}
		else if(BLEDScanCycle < 192){
			PWMB_Duty5(0x0000);
			PWMB_Duty6(BLED_BRIGHT);
			PWMB_Duty7((BLED_BRIGHT >> 6) * (BLEDScanCycle-128));
		}
		else if(BLEDScanCycle < 256){
			PWMB_Duty5(0x0000);
			PWMB_Duty6(BLED_BRIGHT - (BLED_BRIGHT >> 6) * (BLEDScanCycle-192));
			PWMB_Duty7(BLED_BRIGHT);
		}
		else if(BLEDScanCycle < 320){
			PWMB_Duty5((BLED_BRIGHT >> 6) * (BLEDScanCycle-256));
			PWMB_Duty6(0x0000);
			PWMB_Duty7(BLED_BRIGHT);
		}
		else if(BLEDScanCycle < 384){
			PWMB_Duty5(BLED_BRIGHT);
			PWMB_Duty6(0x0000);
			PWMB_Duty7(BLED_BRIGHT - (BLED_BRIGHT >> 6) * (BLEDScanCycle-320));
		}
	}
	else
		BLEDScanCycle = 0;
}

• 本文采用的單片機為STC32G系列，感興趣的朋友可以參考測試，或去Gitee上下載例程。
• 下載地址：https://gitee.com/loganxiang/lgxsmartcar ，參考breathled.h/breathled.c。