STM32MP135裸机编程：定时器内核时钟频率计算方法

0 工具准备

STM32MP13xx参考手册

1 定时器内核时钟频率计算方法

1.1 定时器分组

STM32MP135的定时器按照时钟源不同分成了三组，如下：
APB1:

APB2:

APB6：

1.2 定时器内核时钟频率计算方法

APB1DIV是APB1的分频系数，APB2DIV、APB6DIV同理。TIMG1PRE是第1组定时器的预分频选择，TIMG2PRE、TIMG3PRE同理。相关寄存器如下:
第1组定时器预分频选择寄存器：


第2组定时器预分频选择寄存器：

第3组定时器预分频选择寄存器：


APB1分频系数寄存器：

APB2分频系数寄存器：

APB6分频系数寄存器：

2 定时器内核时钟频率计算操作

以下代码打印stm32MP135所有定时器的内核时钟频率等信息：

/**
 * @brief 获取定时器内核时钟频率
 *
 * @param clock_source_freq 时钟源频率
 * @param bus_div 总线分频值
 * @param timer_pre 定时器预分频值
 * @return float 定时器内核时钟频率
 */
float get_timer_kernel_clock_freq(u32 clock_source_freq, u32 bus_div, u32 timer_pre)
{
    float timer_kernel_clock_freq = 0.0f;
    switch (bus_div)
    {
    case 0:
        timer_kernel_clock_freq = clock_source_freq;
        break;
    case 1:
        timer_kernel_clock_freq = clock_source_freq * 2;
        break;
    case 2:
    case 3:
    case 4:
        if (timer_pre == 0)
        {
            timer_kernel_clock_freq = clock_source_freq * 2;
        }
        else if (timer_pre == 1)
        {
            timer_kernel_clock_freq = clock_source_freq * 4;
        }
    default:
        break;
    }
    return timer_kernel_clock_freq;
}


int clk(void)
{
    float timer_kernel_clock_freq;
    RCC_PeriphCLKInitTypeDef PeriphClkInit;
    HAL_RCCEx_GetPeriphCLKConfig(&PeriphClkInit);

    printf("> Group 1 timer [Clock source : APB1]\r\n");
    printf("  APB1 clock : %0.3f MHz\r\n", (float)HAL_RCC_GetPCLK1Freq() / 1000000.0f);
    printf("  APB1 clock divider : %lu\r\n", RCC->APB1DIVR & 0x7);
    printf("  Group 1 prescaler  : %lu\r\n", RCC->TIMG1PRER & 0x1);
    timer_kernel_clock_freq = get_timer_kernel_clock_freq(HAL_RCC_GetPCLK1Freq(), RCC->APB1DIVR & 0x7, RCC->TIMG1PRER & 0x1) / 1000000.0f;
    printf("  TIM2 TIM3 TIM4 TIM5 TIM6 TIM7 kernel clock freq : %0.3f MHz\r\n", timer_kernel_clock_freq);

    printf("> Group 2 timer [Clock source : APB2]\r\n");
    printf("  APB2 clock : %0.3f MHz\r\n", (float)HAL_RCC_GetPCLK2Freq() / 1000000.0f);
    printf("  APB2 clock divider : %lu\r\n", RCC->APB2DIVR & 0x7);
    printf("  Group 3 prescaler  : %lu\r\n", RCC->TIMG2PRER & 0x1);
    timer_kernel_clock_freq = get_timer_kernel_clock_freq(HAL_RCC_GetPCLK2Freq(), RCC->APB2DIVR & 0x7, RCC->TIMG2PRER & 0x1) / 1000000.0f;
    printf("  TIM1 TIM8 clock freq : %0.3f MHz\r\n", timer_kernel_clock_freq);

    printf("> Group 3 timer [Clock source : APB6]\r\n");
    printf("  APB6 clock : %0.3f MHz\r\n", (float)HAL_RCC_GetPCLK6Freq() / 1000000.0f);
    printf("  APB6 clock divider : %lu\r\n", RCC->APB6DIVR & 0x7);
    printf("  Group 3 prescaler  : %lu\r\n", RCC->TIMG3PRER & 0x1);
    timer_kernel_clock_freq = get_timer_kernel_clock_freq(HAL_RCC_GetPCLK6Freq(), RCC->APB6DIVR & 0x7, RCC->TIMG3PRER & 0x1) / 1000000.0f;
    printf("  TIM12 TIM13 TIM14 TIM15 TIM16 TIM17 kernel clock freq : %0.3f MHz\r\n", timer_kernel_clock_freq);

    return 0;
}
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打印结果如下：