STM32 笔记：PWM

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/**
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 * @brief PWM定时器初始化
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 * @param htim 定时器句柄
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 * @param instance 定时器实例 (TIM3 / TIM8)
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 * @param pwm_hz PWM频率
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 */
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static bool pwm_setup_timer(TIM_HandleTypeDef *htim, TIM_TypeDef *instance, uint32_t pwm_hz)
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{
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    uint32_t tim_clk = timer_get_clock(instance);
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    if (tim_clk == 0U || pwm_hz == 0U) {
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        return false;
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    }
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    htim->Instance = instance;
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    /* 计算预分频器 */
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    uint32_t prescaler = tim_clk / PWM_TICK_HZ;
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    if (prescaler == 0U) prescaler = 1U;
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    /* 计算自动重装值 ARR */
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    uint32_t period = PWM_TICK_HZ / pwm_hz;
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    if (period < 2U) period = 2U;
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    htim->Init.Prescaler = prescaler - 1U;      // 预分频器
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    htim->Init.CounterMode = TIM_COUNTERMODE_UP;// 向上计数
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    htim->Init.Period = period - 1U;            // 自动重装值
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    htim->Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
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    htim->Init.RepetitionCounter = 0;
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    htim->Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;//修改ARR后周期不会突然改变，会在下个周期变化
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    /* 初始化PWM定时器 */
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    return (HAL_TIM_PWM_Init(htim) == HAL_OK);
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}

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/**
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 * @brief PWM GPIO初始化
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 */
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static void pwm_gpio_init(void)
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{
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    __HAL_RCC_GPIOC_CLK_ENABLE();
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    __HAL_RCC_GPIOB_CLK_ENABLE();
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    GPIO_InitTypeDef GPIO_InitStruct = {0};
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    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;     // 复用推挽
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    GPIO_InitStruct.Pull = GPIO_NOPULL;         // 无上下拉
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    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
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    /* TIM3_CH3 - PC8 */
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    GPIO_InitStruct.Pin = timer3_ch3;
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    GPIO_InitStruct.Alternate = GPIO_AF2_TIM3;
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    HAL_GPIO_Init(timer_port, &GPIO_InitStruct);
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    /* TIM3_CH4 - PB1 */
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    GPIO_InitStruct.Pin = timer3_ch4;
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    GPIO_InitStruct.Alternate = GPIO_AF2_TIM3;
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    HAL_GPIO_Init(timer_port1, &GPIO_InitStruct);
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    /* TIM8_CH1/CH2 - PC6/PC7 */
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    GPIO_InitStruct.Pin = timer8_ch1 | timer8_ch2;
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    GPIO_InitStruct.Alternate = GPIO_AF3_TIM8;
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    HAL_GPIO_Init(timer_port, &GPIO_InitStruct);
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}

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/**
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 * @brief 配置PWM通道并启动
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 */
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static bool pwm_config_and_start(TIM_HandleTypeDef *htim, uint32_t channel)
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{
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    TIM_OC_InitTypeDef sConfigOC = {0};
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    sConfigOC.OCMode = TIM_OCMODE_PWM1;        // PWM1模式，输出比较模式
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    sConfigOC.Pulse = 0;                       // 初始占空比0
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    sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;// 高电平有效
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    sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;//关闭 PWM 快速模式
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    /* 配置PWM通道 */
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    if (HAL_TIM_PWM_ConfigChannel(htim, &sConfigOC, channel) != HAL_OK) {
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        return false;
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    }
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    /* 启动PWM输出 */
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    if (HAL_TIM_PWM_Start(htim, channel) != HAL_OK) {
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        return false;
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    }
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    return true;
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}

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/**
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 * @brief 设置PWM占空比
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 * @param ch PWM通道
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 * @param duty 占空比 (0.0 ~ 1.0)
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 */
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void bsp_pwm_write(bsp_pwm_channel_t ch, float duty)
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{
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    if (!pwm_ready || ch >= BSP_PWM_CH_MAX) {
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        return;
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    }
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    TIM_HandleTypeDef *htim = pwm_map[ch].htim;
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    float v = clampf(duty, 0.0f, 1.0f);//限幅0-1
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    uint32_t arr = __HAL_TIM_GET_AUTORELOAD(htim);//获取重装载值
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    uint32_t pulse = (uint32_t)((float)(arr + 1U) * v + 0.5f);
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    if (pulse > arr) pulse = arr;
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  //该函数就是在配置CCR寄存器，把pulse赋值给CCR，其中占空比=CCR/（AAR+1）
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    __HAL_TIM_SET_COMPARE(htim, pwm_map[ch].channel, pulse);
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}