通过PWM控制串行LED灯

说明

本文描述的驱动原理是通用的，但是下文的初始化代码只供参考。

资料下载

RGB_LED灯带_5050慢闪_datasheet

STM32控制LED灯带

根据上面的说明书可知，通过修改800KHz的PWM波形的占空比可以控制LED的颜色。
假设现在有3颗串联起来的灯珠，如下图：

如果U1/U2/U3需要显示红/绿/蓝色，根据说明书，需要从DIN发送0x00FF00_FF0000_0000FF(高位先发)。

假设现在U1/U2/U3需要的颜色为从DIN发送0x123456_789ABC_DEF0AA(高位先发)，则我们需要从DIN输入如下脉冲：
从上面的PWM波形可以看出，PWM的频率一直都是800KHz(周期为1.25us)，但是占空比一直在32%(T0)和68%(T1)两个值中变化。
我们平时使用STM32的PWM输出时，都是设置一个占空比，在有需要的时候再修改占空比，但是这种方式并不能保证每个PWM波形后都更新一次占空比，那怎么办呢？
这就需要使用到我们的HAL_StatusTypeDef HAL_TIMEx_PWMN_Start_DMA(TIM_HandleTypeDef *htim, uint32_t Channel, uint32_t *pData, uint16_t Length);或者HAL_StatusTypeDef HAL_TIM_PWM_Start_DMA(TIM_HandleTypeDef *htim, uint32_t Channel, uint32_t *pData, uint16_t Length);函数了(具体使用哪个，根据占空比需要的高低电平状态决定)。这个函数通过DMA的方式，指定某个定时器的某一通道，发送Length个PWM波形，每个PWM波形高电平的计数值(相当于占空比)存储在pData数组中，当然使用前需要初始化定时器以及相应的DMA外设。

DMA初始化

void Tim8DMAInit(void)
{static DMA_HandleTypeDef hdma_tim_A;__HAL_RCC_DMA2_CLK_ENABLE();/* config led A DMA stream */hdma_tim_A.Init.Channel  = DMA_CHANNEL_7;hdma_tim_A.Init.Direction = DMA_MEMORY_TO_PERIPH;hdma_tim_A.Init.PeriphInc = DMA_PINC_DISABLE;hdma_tim_A.Init.MemInc = DMA_MINC_ENABLE;hdma_tim_A.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;hdma_tim_A.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;hdma_tim_A.Init.Mode = DMA_NORMAL;hdma_tim_A.Init.Priority = DMA_PRIORITY_HIGH;hdma_tim_A.Init.FIFOMode = DMA_FIFOMODE_DISABLE;hdma_tim_A.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;hdma_tim_A.Init.MemBurst = DMA_MBURST_SINGLE;hdma_tim_A.Init.PeriphBurst = DMA_PBURST_SINGLE; /* Set hdma_tim_A instance */hdma_tim_A.Instance = DMA2_Stream4;/* Link hdma_tim_A to hdma[3] (channel3) */__HAL_LINKDMA(&Tim8PwmHandle.TimHandleInit, hdma[3], hdma_tim_A);  //@fixme/* Initialize TIMx DMA handle */HAL_DMA_Init(Tim8PwmHandle.TimHandleInit.hdma[3]);   //@fixme/*##-4- Configure the NVIC for DMA #########################################*/HAL_NVIC_SetPriority(DMA2_Stream4_IRQn, 15, 0);   HAL_NVIC_EnableIRQ(DMA2_Stream4_IRQn);BSP_IntVectSet(DMA2_Stream4_IRQn, DMA2_Stream4_IRQHandler);
}

TIM初始化

void Tim8PwmConfig(void)
{Tim8PwmHandle.TimHandleInit.Instance               = TIM8;Tim8PwmHandle.TimHandleInit.Init.Prescaler          = 1;       // 系统时钟到TIM的分频系数，由于TIM8是挂在APB2总线上，而APB2总线最高时钟不能超过90MHz，系统时钟配置为168MHz，所以设置为1分频，即TIM8的时钟为84MHz。Tim8PwmHandle.TimHandleInit.Init.Period             = 105 - 1; // PWM周期，105 * 800KHz = 84MHzTim8PwmHandle.TimHandleInit.Init.RepetitionCounter     = 0;    // 不需要重加载Tim8PwmHandle.TimHandleInit.Init.ClockDivision        = 0;    // 定时器时钟不需要分频Tim8PwmHandle.TimHandleInit.Init.CounterMode          = TIM_COUNTERMODE_UP;   // 向上计数Tim8PwmHandle.TimClkEnable                          = Tim8ClkEnable;        // 使能定时器时钟的函数指针Tim8PwmHandle.PwmChannel1.EnableFlag                = false;Tim8PwmHandle.PwmChannel2.EnableFlag               = false;Tim8PwmHandle.PwmChannel4.EnableFlag               = false;/** channel 3 使能 **/Tim8PwmHandle.PwmChannel3.EnableFlag               = true;Tim8PwmHandle.PwmChannel3.GpioClkInit               = Tim8Channel3ClkEnable;    // 通道1的GPIO时钟使能Tim8PwmHandle.PwmChannel3.GpioInit.Pin              = GPIO_PIN_15;Tim8PwmHandle.PwmChannel3.GpioInit.Mode              = GPIO_MODE_AF_PP;Tim8PwmHandle.PwmChannel3.GpioInit.Pull              = GPIO_PULLDOWN;Tim8PwmHandle.PwmChannel3.GpioInit.Speed           = GPIO_SPEED_FAST;Tim8PwmHandle.PwmChannel3.GpioInit.Alternate     = GPIO_AF3_TIM8;Tim8PwmHandle.PwmChannel3.GpioPort                 = GPIOH;Tim8PwmHandle.PwmChannel3.OConfig.OCMode           = TIM_OCMODE_PWM1;Tim8PwmHandle.PwmChannel3.OConfig.OCNPolarity        = TIM_OCNPOLARITY_HIGH;Tim8PwmHandle.PwmChannel3.OConfig.OCFastMode        = TIM_OCFAST_ENABLE;Tim8PwmHandle.PwmChannel3.OConfig.OCIdleState       = TIM_OCIDLESTATE_RESET;Tim8PwmHandle.PwmChannel3.OConfig.OCNIdleState      = TIM_OCNIDLESTATE_SET;Tim8PwmHandle.PwmChannel3.OConfig.Pulse               = 0;if(BspPwmHandleInit(&Tim8PwmHandle) != HAL_OK){}  // todoTim8DMAInit();
}

LED颜色控制逻辑

#define PWM_LOW     34          // 根据LED的datasheet，T0的占空比为'0.4/1.25=32%'，所以需要'105*32%=34'个计数
#define PWM_HIGH    71          // 根据LED的datasheet，T1的占空比为'0.85/1.25=68%'，所以需要'105*68%=71'个计数
bool ledAFinishFlag = true;     // LED颜色控制的PWM波形是否已经发送完成
typedef struct
{u32 LedMaxNum;         // LED串联的个数u32 *LedInfoBuff;        // LED色素缓存数组，每个灯需要24位空间(实际分配位u32类型)，所以这个指针指向"u32 LedInfoBuff[LedMaxNum]"类型u32 *PWMValueBuff;        // 有LedMaxMum个灯，每个灯有24位表示颜色，每个位都对应了一个PWM，而这个PWM的占空比是一个u32类型的值，所以这个指针指向"u32 PWMValueBuff[LedMaxNum*24]"类型
} LEDHandleDef;BspLEDStatusTypeDef PWMValueGet(LEDHandleDef *LEDHandle)
{u32 i, j;if(LEDHandle == NULL)return LED_HANDLE_ERR;for(i = 0; i < LEDHandle->LedMaxNum; i++){for(j = 0; j < 24; j++){if(LEDHandle->LedInfoBuff[i] & (0x00800000u >> j))  // 根据某一位的值设置相应的占空比计数LEDHandle->PWMValueBuff[i*24 + j] = PWM_HIGH;elseLEDHandle->PWMValueBuff[i*24 + j] = PWM_LOW;}}return LED_GET_DATA_OK;
}BspLEDStatusTypeDef ledDealA(LEDHandleDef *LEDHandle)
{u32 i;while(ledAFinishFlag != true)   // 等待上次LED颜色发送完成，这个值在void HAL_TIM_PWM_PulseFinishedCallback(TIM_HandleTypeDef *htim)函数中赋值为true{}// 将所有灯的颜色都设置为 0x000000 颜色for(i = 0; i < LEDHandle->LedMaxNum * 24; i++){LEDHandle->PWMValueBuff[i] = PWM_LOW;}// if(  HAL_TIM_PWM_Start_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3, (u32*)LEDHandle->PWMValueBuff, LEDHandle->LedMaxNum * 24) != HAL_OK)if(  HAL_TIMEx_PWMN_Start_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3, (u32*)LEDHandle->PWMValueBuff, LEDHandle->LedMaxNum * 24) != HAL_OK)return LED_HAL_ERR;elseledAFinishFlag = false;while(ledAFinishFlag != true)   // 等待LED颜色重置完成{}// 根据每个LED的颜色值计算其占空比的计数值PWMValueGet(&LEDHandleA);// 按需求设置LED颜色// if(  HAL_TIM_PWM_Start_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3, (u32*)LEDHandle->PWMValueBuff, LEDHandle->LedMaxNum * 24) != HAL_OK)if(  HAL_TIMEx_PWMN_Start_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3, (u32*)LEDHandle->PWMValueBuff, LEDHandle->LedMaxNum * 24) != HAL_OK)   return LED_HAL_ERR;elseledAFinishFlag = false;return LED_DEAL_OK;
}void SetLedPartAColor(u8 ledRed, u8 ledGreen, u8 ledBlue)
{u8 j = 0;u32 uTmpColor = 0;uTmpColor = ((ledGreen<<16) | (ledRed<<8) | (ledBlue));     // 根据datasheet，给LED发送的颜色顺序是GRBfor(j = 0; j < LED_NUM; j++){gLedAInfoBuff[j] = uTmpColor;}LEDHandleA.LedMaxNum = LED_NUM;LEDHandleA.LedInfoBuff = gLedAInfoBuff;LEDHandleA.PWMValueBuff = gLedAPwmvalBuff;ledDealA(&LEDHandleA);
}/*
* @brief:   Led灯带颜色设置
* @input:   color[31-24] - don't care
*           color[23-16] - R
*           color[15-8]  - G
*           color[7-0]   - B
* @return:  None
*/
static void LedStripePartAColorSet(const u32 color)
{u8  R = 0, G = 0, B = 0;R = (u8)((color>>16) & 0xFF);G = (u8)((color >> 8) & 0xFF);B = (u8)((color ) & 0xFF);SetLedPartAColor(R, G, B);
}void HAL_TIM_PWM_PulseFinishedCallback(TIM_HandleTypeDef *htim)
{if(htim->Instance == TIM8){if(htim->Channel == HAL_TIM_ACTIVE_CHANNEL_1){
//          HAL_TIM_PWM_Stop_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_1);HAL_TIMEx_PWMN_Stop_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_1);ledFinishFlag = true;Tim8PwmHandle.TimHandleInit.Instance->CCR1  = 0;Tim8PwmHandle.TimHandleInit.Instance->EGR = TIM_EGR_UG;}if(htim->Channel == HAL_TIM_ACTIVE_CHANNEL_3){
//          HAL_TIM_PWM_Stop_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3);HAL_TIMEx_PWMN_Stop_DMA(&Tim8PwmHandle.TimHandleInit, TIM_CHANNEL_3);ledAFinishFlag = true;Tim8PwmHandle.TimHandleInit.Instance->CCR3 = 0;Tim8PwmHandle.TimHandleInit.Instance->EGR = TIM_EGR_UG;}       }
}