ADC — 定时器触发自动抢占

固件库: AT32F403A_407_Firmware_Library V2.2.2
芯片: AT32
源文件: AT32/AT32F403A_407_Firmware_Library_V2.2.2/project/at_start_f403a/examples/adc/tmr_trigger_automatic_preempted/src/main.c

功能简介

本示例演示 ADC 模数转换器的基本用法。ADC 将模拟电压信号转换为数字值，是读取传感器数据的关键外设。

硬件准备

电位器（可调电阻）连接到 ADC 输入引脚
或使用内部温度传感器（无需额外硬件）

完整代码

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#include "at32f403a_407_board.h"
#include "at32f403a_407_clock.h"
__IO uint16_t adc1_ordinary_valuetab[3] = {0};
__IO uint16_t adc1_preempt_valuetab[3] = {0};
__IO uint16_t dma_trans_complete_flag = 0;
__IO uint16_t ordinary_conversion_times_index = 0;
__IO uint16_t preempt_conversion_count = 0;
__IO uint16_t preempt_conversion_times_index = 0;

static void gpio_config(void)
{
  gpio_init_type gpio_initstructure;
  crm_periph_clock_enable(CRM_GPIOA_PERIPH_CLOCK, TRUE);
  crm_periph_clock_enable(CRM_GPIOB_PERIPH_CLOCK, TRUE);

  gpio_default_para_init(&gpio_initstructure);
  gpio_initstructure.gpio_mode = GPIO_MODE_ANALOG;
  gpio_initstructure.gpio_pins = GPIO_PINS_4 | GPIO_PINS_5 | GPIO_PINS_6 | GPIO_PINS_7;
  gpio_init(GPIOA, &gpio_initstructure);

  gpio_initstructure.gpio_mode = GPIO_MODE_ANALOG;
  gpio_initstructure.gpio_pins = GPIO_PINS_0 | GPIO_PINS_1;
  gpio_init(GPIOB, &gpio_initstructure);
}

static void dma_config(void)
{
  dma_init_type dma_init_struct;
  crm_periph_clock_enable(CRM_DMA1_PERIPH_CLOCK, TRUE);
  nvic_irq_enable(DMA1_Channel1_IRQn, 0, 0);
  dma_reset(DMA1_CHANNEL1);
  dma_default_para_init(&dma_init_struct);
  dma_init_struct.buffer_size = 3;
  dma_init_struct.direction = DMA_DIR_PERIPHERAL_TO_MEMORY;
  dma_init_struct.memory_base_addr = (uint32_t)adc1_ordinary_valuetab;
  dma_init_struct.memory_data_width = DMA_MEMORY_DATA_WIDTH_HALFWORD;
  dma_init_struct.memory_inc_enable = TRUE;
  dma_init_struct.peripheral_base_addr = (uint32_t)&(ADC1->odt);
  dma_init_struct.peripheral_data_width = DMA_PERIPHERAL_DATA_WIDTH_HALFWORD;
  dma_init_struct.peripheral_inc_enable = FALSE;
  dma_init_struct.priority = DMA_PRIORITY_HIGH;
  dma_init_struct.loop_mode_enable = TRUE;
  dma_init(DMA1_CHANNEL1, &dma_init_struct);

  dma_interrupt_enable(DMA1_CHANNEL1, DMA_FDT_INT, TRUE);
}

static void tmr1_config(void)
{
  gpio_init_type gpio_initstructure;
  tmr_output_config_type tmr_oc_init_structure;
  crm_clocks_freq_type crm_clocks_freq_struct = {0};
  crm_periph_clock_enable(CRM_GPIOA_PERIPH_CLOCK, TRUE);

  gpio_default_para_init(&gpio_initstructure);
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_8;
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_pull = GPIO_PULL_NONE;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  gpio_init(GPIOA, &gpio_initstructure);

  /* get system clock */
  crm_clocks_freq_get(&crm_clocks_freq_struct);

  crm_periph_clock_enable(CRM_TMR1_PERIPH_CLOCK, TRUE);

  /* (systemclock/(systemclock/10000))/10000 = 1Hz(1s) */
  tmr_base_init(TMR1, 9999, (crm_clocks_freq_struct.sclk_freq/10000 - 1));
  tmr_cnt_dir_set(TMR1, TMR_COUNT_UP);
  tmr_clock_source_div_set(TMR1, TMR_CLOCK_DIV1);

  tmr_output_default_para_init(&tmr_oc_init_structure);
  tmr_oc_init_structure.oc_mode = TMR_OUTPUT_CONTROL_PWM_MODE_A;
  tmr_oc_init_structure.oc_polarity = TMR_OUTPUT_ACTIVE_LOW;
  tmr_oc_init_structure.oc_output_state = TRUE;
  tmr_oc_init_structure.oc_idle_state = FALSE;
  tmr_output_channel_config(TMR1, TMR_SELECT_CHANNEL_1, &tmr_oc_init_structure);
  tmr_channel_value_set(TMR1, TMR_SELECT_CHANNEL_1, 5000);
}

static void adc_config(void)
{
  adc_base_config_type adc_base_struct;
  crm_periph_clock_enable(CRM_ADC1_PERIPH_CLOCK, TRUE);
  adc_reset(ADC1);
  crm_adc_clock_div_set(CRM_ADC_DIV_4);
  nvic_irq_enable(ADC1_2_IRQn, 0, 0);
  adc_base_default_para_init(&adc_base_struct);

  /* select combine mode */
  adc_combine_mode_select(ADC_INDEPENDENT_MODE);

  /* ADC1 config */
  adc_base_struct.sequence_mode = TRUE;
  adc_base_struct.repeat_mode = FALSE;
  adc_base_struct.data_align = ADC_RIGHT_ALIGNMENT;
  adc_base_struct.ordinary_channel_length = 3;
  adc_base_config(ADC1, &adc_base_struct);
  adc_ordinary_channel_set(ADC1, ADC_CHANNEL_4, 1, ADC_SAMPLETIME_239_5);
  adc_ordinary_channel_set(ADC1, ADC_CHANNEL_5, 2, ADC_SAMPLETIME_239_5);
  adc_ordinary_channel_set(ADC1, ADC_CHANNEL_6, 3, ADC_SAMPLETIME_239_5);
  adc_ordinary_conversion_trigger_set(ADC1, ADC12_ORDINARY_TRIG_TMR1CH1, TRUE);
  adc_dma_mode_enable(ADC1, TRUE);

  adc_preempt_channel_length_set(ADC1, 3);
  adc_preempt_channel_set(ADC1, ADC_CHANNEL_7, 1, ADC_SAMPLETIME_239_5);
  adc_preempt_channel_set(ADC1, ADC_CHANNEL_8, 2, ADC_SAMPLETIME_239_5);
  adc_preempt_channel_set(ADC1, ADC_CHANNEL_9, 3, ADC_SAMPLETIME_239_5);
  adc_preempt_conversion_trigger_set(ADC1, ADC12_PREEMPT_TRIG_SOFTWARE, TRUE);
  adc_preempt_auto_mode_enable(ADC1, TRUE);
  adc_interrupt_enable(ADC1, ADC_PCCE_INT, TRUE);

  adc_enable(ADC1, TRUE);

  /* ADC calibration */
  adc_calibration_init(ADC1);
  while(adc_calibration_init_status_get(ADC1));
  adc_calibration_start(ADC1);
  while(adc_calibration_status_get(ADC1));
}

int main(void)
{
  nvic_priority_group_config(NVIC_PRIORITY_GROUP_4);
  system_clock_config();
  at32_board_init();
  at32_led_off(LED2);
  at32_led_off(LED3);
  at32_led_off(LED4);
  uart_print_init(115200);
  gpio_config();
  tmr1_config();
  dma_config();
  adc_config();

  /* enable DMA after ADC activation */
  dma_channel_enable(DMA1_CHANNEL1, TRUE);

  printf("tmr_trigger_automatic_preempted \r\n");
  tmr_counter_enable(TMR1, TRUE);
  tmr_channel_enable(TMR1, TMR_SELECT_CHANNEL_1, TRUE);
  tmr_output_enable(TMR1, TRUE);
  while(1)
  {
    /* wait ordinary conversion end */
    if(ordinary_conversion_times_index != dma_trans_complete_flag)
    {
      ordinary_conversion_times_index = dma_trans_complete_flag;
      printf("ordinary_conversion_times_index = %d\r\n",ordinary_conversion_times_index);
      printf("adc1_ordinary_valuetab[0] = 0x%x\r\n", adc1_ordinary_valuetab[0]);
      printf("adc1_ordinary_valuetab[1] = 0x%x\r\n", adc1_ordinary_valuetab[1]);
      printf("adc1_ordinary_valuetab[2] = 0x%x\r\n", adc1_ordinary_valuetab[2]);
      printf("\r\n");
      at32_led_toggle(LED2);
    }

    /* wait preempt conversion end */
    if(preempt_conversion_times_index != preempt_conversion_count)
    {
      preempt_conversion_times_index = preempt_conversion_count;
      printf("preempt_conversion_times_index = %d\r\n",preempt_conversion_times_index);
      printf("adc1_preempt_valuetab[0] = 0x%x\r\n", adc1_preempt_valuetab[0]);
      printf("adc1_preempt_valuetab[1] = 0x%x\r\n", adc1_preempt_valuetab[1]);
      printf("adc1_preempt_valuetab[2] = 0x%x\r\n", adc1_preempt_valuetab[2]);
      printf("\r\n");
      at32_led_toggle(LED3);
    }
  }
}

代码讲解

系统时钟初始化：配置 MCU 的主频和时钟树。不同芯片的时钟配置不同，一般由工具生成。

板级初始化：初始化开发板上的 LED、按键等基础外设。

串口初始化：配置串口波特率（这里是 115200），使能 printf 重定向。

printf 输出：通过串口打印调试信息。需要先调用 uart_print_init 完成重定向。

GPIO 配置：设置引脚为输出/输入模式，选择推挽/开漏输出，配置上拉/下拉。

ADC 配置：选择采样通道、采样时间、触发方式、数据对齐方式。采样时间越长精度越高。

DMA 配置：设置源地址、目标地址、传输方向、数据宽度。DMA 搬运数据不占用 CPU。

定时器配置：设置预分频器（PSC）和重装载值（ARR），定时时间 = (PSC+1) × (ARR+1) / 时钟频率。

PWM 配置：在定时器基础上设置比较值（CCR），占空比 = CCR / (ARR+1)。CCR 越大占空比越高。

中断优先级配置：NVIC 设置中断的抢占优先级和子优先级。数字越小优先级越高。

校准：ADC 使用前必须校准，消除工艺偏差。校准期间不要操作 ADC。

实验现象

串口助手打印 ADC 采样值
转动电位器时数值变化
温度传感器示例会显示芯片温度

注意事项

ADC 参考电压影响测量精度
采样时间要根据信号源阻抗选择
使用前务必校准（Calibration）

AT32 ADC — 定时器触发自动抢占

AT32 AT32F403A_407_Firmware_Library V2.2.2 ADC 定时器触发自动抢占示例教学