使用Platformio平台的libopencm3开发框架来开发STM32G0，以下为多通道ADC与DMA的使用。

1 新建项目

• 建立adc_dma项目
  
  

在PIO的Home页面新建项目，项目名称adc_dma，选择开发板为 MonkeyPi_STM32_G070RB，开发框架选择libopencm3；

• 项目建立完成后在src目录下新建main.c主程序文件；
• 修改下载和调试方式，这里开发板使用的是DAPLink仿真器，因此修改platformio.ini文件如下：
  
  

1. 1upload_protocol = cmsis-dap
   
2. 2debug_tool = cmsis-dap

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2 编写程序2.1 ADC 设置

这里设置PA0、PA1、PA2、PA3四个引脚为ADC：

1. 1static void adc_setup(void)
   
2. 2{
   
3. 3    rcc_periph_clock_enable(RCC_ADC);
   
4. 4    rcc_periph_clock_enable(RCC_GPIOA);
   
5. 5
   
6. 6    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO0);
   
7. 7    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO1);
   
8. 8    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO2);
   
9. 9    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO3);
   
10. 10
    
11. 11    adc_power_off(ADC1);
    
12. 12    adc_set_clk_prescale(ADC1, ADC_CCR_PRESC_DIV2);
    
13. 13    adc_set_single_conversion_mode(ADC1);
    
14. 14    adc_set_right_aligned(ADC1);
    
15. 15    adc_set_sample_time_on_all_channels(ADC1, ADC_SMPTIME_160DOT5);
    
16. 16
    
17. 17    uint8_t channel_array[16] = {0};
    
18. 18    channel_array[0] = 0;
    
19. 19    channel_array[1] = 1;
    
20. 20    channel_array[2] = 2;
    
21. 21    channel_array[3] = 3;
    
22. 22    adc_set_regular_sequence(ADC1, ADC_CHAN_CNT, channel_array);
    
23. 23    adc_enable_dma_circular_mode(ADC1);
    
24. 24    adc_set_resolution(ADC1, ADC_CFGR1_RES_12_BIT);
    
25. 25    adc_power_on(ADC1);
    
26. 26
    
27. 27    /* Wait for ADC starting up. */
    
28. 28    delay_ms(10);
    
29. 29}

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2.2 DMA配置

1. 1static void dma_setup(void *data, int size)
   
2. 2{
   
3. 3    dma_channel_reset(DMA1, DMA_CHANNEL1);
   
4. 4    dma_set_peripheral_address(DMA1, DMA_CHANNEL1, (uint32_t)&ADC_DR(ADC1));
   
5. 5    dma_set_memory_address(DMA1, DMA_CHANNEL1, (uint32_t)data);
   
6. 6    dma_set_number_of_data(DMA1, DMA_CHANNEL1, size);
   
7. 7    dma_set_read_from_peripheral(DMA1, DMA_CHANNEL1);
   
8. 8    dma_enable_memory_increment_mode(DMA1, DMA_CHANNEL1);
   
9. 9    dma_set_peripheral_size(DMA1, DMA_CHANNEL1, DMA_CCR_PSIZE_16BIT);
   
10. 10    dma_set_memory_size(DMA1, DMA_CHANNEL1, DMA_CCR_MSIZE_16BIT);
    
11. 11    dma_enable_circular_mode(DMA1, DMA_CHANNEL1);
    
12. 12    dma_enable_transfer_complete_interrupt(DMA1, DMA_CHANNEL1);
    
13. 13    dma_enable_channel(DMA1, DMA_CHANNEL1);
    
14. 14
    
15. 15    dmamux_reset_dma_channel(DMAMUX1, DMA_CHANNEL1);
    
16. 16    dmamux_set_dma_channel_request(DMAMUX1, DMA_CHANNEL1, DMAMUX_CxCR_DMAREQ_ID_ADC);
    
17. 17}

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主要是设置DMA的外设地址为ADC数据寄存器 ADC_DR；并设置内存地址为定义的buff，size为需要缓存的数据大小：

1. 1#define ADC_CHAN_CNT        4
   
2. 2#define ADC_FILETER_SIZE    32
   
3. 3
   
4. 4int16_t adc_values[ADC_FILETER_SIZE*ADC_CHAN_CNT];

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2.3 ADC配置为DMA读取和Timer触发

• 定时器设置
  
  

1. 1void tim3_setup(void)
   
2. 2{
   
3. 3    /* Enable TIM3 clock. */
   
4. 4    rcc_periph_clock_enable(RCC_TIM3);
   
5. 5
   
6. 6    /* Enable TIM3 interrupt. */
   
7. 7    nvic_enable_irq(NVIC_TIM3_IRQ);
   
8. 8
   
9. 9    /* Reset TIM3 peripheral to defaults. */
   
10. 10    rcc_periph_reset_pulse(RST_TIM3);
    
11. 11
    
12. 12    /* Timer global mode:
    
13. 13     * - No divider
    
14. 14     * - Alignment edge
    
15. 15     * - Direction up
    
16. 16     * (These are actually default values after reset above, so this call
    
17. 17     * is strictly unnecessary, but demos the api for alternative settings)
    
18. 18     */
    
19. 19    timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT,
    
20. 20                   TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
    
21. 21
    
22. 22    /*
    
23. 23     * Please take note that the clock source for STM32 timers
    
24. 24     * might not be the raw APB1/APB2 clocks.  In various conditions they
    
25. 25     * are doubled.  See the Reference Manual for full details!
    
26. 26     * In our case, TIM3 on APB1 is running at double frequency, so this
    
27. 27     * sets the prescaler to have the timer run at 5kHz
    
28. 28     */
    
29. 29    timer_set_prescaler(TIM3, 64-1);
    
30. 30
    
31. 31    /* Disable preload. */
    
32. 32    timer_disable_preload(TIM3);
    
33. 33    timer_continuous_mode(TIM3);
    
34. 34
    
35. 35    timer_set_period(TIM3, 20000-1); //100Hz
    
36. 36
    
37. 37    timer_set_master_mode(TIM3, TIM_CR2_MMS_UPDATE);
    
38. 38
    
39. 39    timer_enable_irq(TIM3, TIM_DIER_UIE);
    
40. 40}
    
41. 41
    
42. 42void tim3_enable_counter(bool en)
    
43. 43{
    
44. 44    if(en){
    
45. 45        timer_enable_counter(TIM3);
    
46. 46    }else{
    
47. 47        timer_disable_counter(TIM3);
    
48. 48    }
    
49. 49}
    
50. 50
    
51. 51void tim3_isr(void)
    
52. 52{
    
53. 53    if (timer_get_flag(TIM3, TIM_SR_UIF)) {
    
54. 54
    
55. 55        /* Clear compare interrupt flag. */
    
56. 56        timer_clear_flag(TIM3, TIM_SR_UIF);
    
57. 57    }
    
58. 58}

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• DMA设置和Timer触发
  
  

1. 1    rcc_periph_clock_enable(RCC_DMA);
   
2. 2    nvic_set_priority(NVIC_DMA1_CHANNEL1_IRQ, 3);
   
3. 3    nvic_enable_irq(NVIC_DMA1_CHANNEL1_IRQ);
   
4. 4
   
5. 5    adc_setup();
   
6. 6
   
7. 7    dma_setup(adc_values, ADC_CHAN_CNT*ADC_FILETER_SIZE);
   
8. 8
   
9. 9    adc_enable_overrun_interrupt(ADC1);
   
10. 10
    
11. 11    adc_enable_dma(ADC1);
    
12. 12
    
13. 13    ADC_CFGR1(ADC1) = (ADC_CFGR1(ADC1) & ~(0x3<<10)) | (0x1<<10);    // Hardware trigger detection on the rising edge
    
14. 14    ADC_CFGR1(ADC1) = (ADC_CFGR1(ADC1) & ~ADC_CFGR1_EXTSEL) | (3<<ADC_CFGR1_EXTSEL_SHIFT);    // toggle by tim3
    
15. 15
    
16. 16    tim3_setup();
    
17. 17
    
18. 18    adc_start_conversion_regular(ADC1);
    
19. 19
    
20. 20
    
21. 21    tim3_enable_counter(true);
    
22. 22
    
23. 23    delay_ms(100);

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DMA中断时候即准备好读取ADC数据，因此在DMA中断中先把定时器关闭，读取数据后再次打开：

1. 1void dma1_channel1_isr(void)
   
2. 2{
   
3. 3
   
4. 4    if ((DMA1_ISR &DMA_ISR_TCIF1) != 0) {
   
5. 5        DMA1_IFCR |= DMA_IFCR_CTCIF1;
   
6. 6    }
   
7. 7
   
8. 8    tim3_enable_counter(false);
   
9. 9
   
10. 10}

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2.4 ADC读取

1. 1void adc_sample(void)
   
2. 2{
   
3. 3    uint32_t sum_val1 = 0;
   
4. 4    uint32_t sum_val2 = 0;
   
5. 5    uint32_t sum_val3 = 0;
   
6. 6    uint32_t sum_val4 = 0;
   
7. 7
   
8. 8    for(int i=0; i<ADC_FILETER_SIZE; i++){
   
9. 9        sum_val1 += adc_values[ADC_CHAN_CNT*i + 0];
   
10. 10        sum_val2 += adc_values[ADC_CHAN_CNT*i + 1];
    
11. 11        sum_val3 += adc_values[ADC_CHAN_CNT*i + 2];
    
12. 12        sum_val4 += adc_values[ADC_CHAN_CNT*i + 3];
    
13. 13    }
    
14. 14
    
15. 15    uint32_t filter_val1 = sum_val1/ADC_FILETER_SIZE;
    
16. 16    uint32_t filter_val2 = sum_val2/ADC_FILETER_SIZE;
    
17. 17    uint32_t filter_val3 = sum_val3/ADC_FILETER_SIZE;
    
18. 18    uint32_t filter_val4 = sum_val4/ADC_FILETER_SIZE;
    
19. 19
    
20. 20    printf("adc:%d  %d  %d  %d\r\n", filter_val1, filter_val2, filter_val3, filter_val4);
    
21. 21
    
22. 22    tim3_enable_counter(true);
    
23. 23}

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读取时候按照通道的顺序从buff中取出，这里做了简单的过滤；

3 烧写测试

将程序烧写到开发板，然后打开串口可以看到四个ADC通道的数据，在PA0/PA1/PA3/PA4四个引脚连接不同电压可以看到变化：

转载自：MakerInChina.cn