我使用了STM32Cube初始化代码生成器来生成一个已初始化的定时器函数。为了生成一个固定占空比的PWM信号，我在定时器初始化函数中添加了HAL_TIM_Base_Start(&htim1); //启动TIM基础生成和HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1)//启动PWM信号生成，如下所示。
/* Private variables ---------------------------------------------------------*/
int pulse_width=0;
/* TIM1 init function */
static void MX_TIM1_Init(void)
{
TIM_ClockConfigTypeDef sClockSourceConfig;
TIM_MasterConfigTypeDef sMasterConfig;
TIM_OC_InitTypeDef sConfigOC;
TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig;
htim1.Instance = TIM1;
htim1.Init.Prescaler = 0;//we want a max frequency for timer, so we set prescaller to 0
//And our timer will have tick frequency
htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
htim1.Init.Period = 1066;//max value for timer is 16bit = 65535, TIM_Period = timer_tick_frequency / PWM_frequency - 1
//In our case, for 15Khz PWM_frequency, set Period to TIM_Period = 16MHz / 15KHz - 1 = 1066
htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim1.Init.RepetitionCounter = 0;
if (HAL_TIM_Base_Init(&htim1) != HAL_OK)/* to use the Timer to generate a simple time base for TIM1 */
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;//the default clock is the internal clock from the APBx, using this function
if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)//Initializes the TIM PWM Time Base according to the specified
//parameters in the TIM_HandleTypeDef and create the associated handle.
{
Error_Handler();
}
if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
//sConfig: TIM PWM configuration structure
//set duty cycle: pulse_length = ((1066 + 1) * duty_cycle) / (100 - 1)
sConfigOC.OCMode = TIM_OCMODE_PWM1;
sConfigOC.Pulse = pulse_width;/* 50% duty cycle is 538, set to 0 initially*///
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)
{
Error_Handler();
}
sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_ENABLE;
sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_ENABLE;
sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_1;
sBreakDeadTimeConfig.DeadTime = 0;
sBreakDeadTimeConfig.BreakState = TIM_BREAK_ENABLE;
sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_ENABLE;
if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
{
Error_Handler();
}
HAL_TIM_MspPostInit(&htim1);//output pin assignment
HAL_TIM_Base_Start(&htim1); //Starts the TIM Base generation
if (HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1) != HAL_OK)//Starts the PWM signal generation
{
/* PWM Generation Error */
Error_Handler();
}
/* Start channel 2 */
if (HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2) != HAL_OK)
{
/* PWM Generation Error */
Error_Handler();
}
}
当我在sConfigOC.Pulse = pulse_width中硬编码正确的值来替换pulse_width值时，就足以使PWM以注释中指定的固定占空比运行。
在另一个函数中，我有一个算法来更新全局变量pulse_width。该函数名为：adjust_PWM();。该算法计算从ADC测量并存储为全局变量的值。该函数名为：Data_Update();。在main()中，在所有函数初始化完成后，我无限调用这三个函数。
Data_Update();
adjust_PWM();
MX_TIM1_Init();
我尝试过这个方法，但示波器上得到的波形很奇怪，这可能是因为ADC引脚悬空导致浮动测量干扰了算法的占空比。此外，不断调用计时器的初始化会中断PWM信号。有没有更好的方法在运行代码时改变占空比，而不使用全局变量或每次更新占空比时都要初始化计时器？如果有相关链接，请分享。