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：
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upload_protocol = cmsis-dap
debug_tool = cmsis-dap

2 编写程序

2.1 ADC 设置

这里设置PA0、PA1、PA2、PA3四个引脚为ADC：

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static void adc_setup(void)
{
    rcc_periph_clock_enable(RCC_ADC);
    rcc_periph_clock_enable(RCC_GPIOA);

    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO0);
    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO1);
    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO2);
    gpio_mode_setup(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO3);

    adc_power_off(ADC1);
    adc_set_clk_prescale(ADC1, ADC_CCR_PRESC_DIV2);
    adc_set_single_conversion_mode(ADC1);
    adc_set_right_aligned(ADC1);
    adc_set_sample_time_on_all_channels(ADC1, ADC_SMPTIME_160DOT5);

    uint8_t channel_array[16] = {0};
    channel_array[0] = 0;
    channel_array[1] = 1;
    channel_array[2] = 2;
    channel_array[3] = 3;
    adc_set_regular_sequence(ADC1, ADC_CHAN_CNT, channel_array);
    adc_enable_dma_circular_mode(ADC1);
    adc_set_resolution(ADC1, ADC_CFGR1_RES_12_BIT);
    adc_power_on(ADC1);

    /* Wait for ADC starting up. */
    delay_ms(10); 
}
2.2 DMA配置
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static void dma_setup(void *data, int size)
{
    dma_channel_reset(DMA1, DMA_CHANNEL1);
    dma_set_peripheral_address(DMA1, DMA_CHANNEL1, (uint32_t)&ADC_DR(ADC1));
    dma_set_memory_address(DMA1, DMA_CHANNEL1, (uint32_t)data);
    dma_set_number_of_data(DMA1, DMA_CHANNEL1, size);
    dma_set_read_from_peripheral(DMA1, DMA_CHANNEL1);
    dma_enable_memory_increment_mode(DMA1, DMA_CHANNEL1);
    dma_set_peripheral_size(DMA1, DMA_CHANNEL1, DMA_CCR_PSIZE_16BIT);
    dma_set_memory_size(DMA1, DMA_CHANNEL1, DMA_CCR_MSIZE_16BIT);
    dma_enable_circular_mode(DMA1, DMA_CHANNEL1);
    dma_enable_transfer_complete_interrupt(DMA1, DMA_CHANNEL1);
    dma_enable_channel(DMA1, DMA_CHANNEL1);

    dmamux_reset_dma_channel(DMAMUX1, DMA_CHANNEL1);
    dmamux_set_dma_channel_request(DMAMUX1, DMA_CHANNEL1, DMAMUX_CxCR_DMAREQ_ID_ADC);
}

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：

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#define ADC_CHAN_CNT        4
#define ADC_FILETER_SIZE    32

int16_t adc_values[ADC_FILETER_SIZE*ADC_CHAN_CNT];
2.3 ADC配置为DMA读取和Timer触发
  • 定时器设置
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void tim3_setup(void)
{
    /* Enable TIM3 clock. */
    rcc_periph_clock_enable(RCC_TIM3);

    /* Enable TIM3 interrupt. */
    nvic_enable_irq(NVIC_TIM3_IRQ);

    /* Reset TIM3 peripheral to defaults. */
    rcc_periph_reset_pulse(RST_TIM3);

    /* Timer global mode:
     * - No divider
     * - Alignment edge
     * - Direction up
     * (These are actually default values after reset above, so this call
     * is strictly unnecessary, but demos the api for alternative settings)
     */
    timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT,
                   TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);

    /*
     * Please take note that the clock source for STM32 timers
     * might not be the raw APB1/APB2 clocks.  In various conditions they
     * are doubled.  See the Reference Manual for full details!
     * In our case, TIM3 on APB1 is running at double frequency, so this
     * sets the prescaler to have the timer run at 5kHz
     */
    timer_set_prescaler(TIM3, 64-1);

    /* Disable preload. */
    timer_disable_preload(TIM3);
    timer_continuous_mode(TIM3);

    timer_set_period(TIM3, 20000-1); //100Hz

    timer_set_master_mode(TIM3, TIM_CR2_MMS_UPDATE);

    timer_enable_irq(TIM3, TIM_DIER_UIE);
}

void tim3_enable_counter(bool en)
{
    if(en){
        timer_enable_counter(TIM3);
    }else{
        timer_disable_counter(TIM3);
    }
}

void tim3_isr(void)
{
    if (timer_get_flag(TIM3, TIM_SR_UIF)) {

        /* Clear compare interrupt flag. */
        timer_clear_flag(TIM3, TIM_SR_UIF);
    }
}
  • DMA设置和Timer触发
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rcc_periph_clock_enable(RCC_DMA);
nvic_set_priority(NVIC_DMA1_CHANNEL1_IRQ, 3);
nvic_enable_irq(NVIC_DMA1_CHANNEL1_IRQ);

adc_setup();

dma_setup(adc_values, ADC_CHAN_CNT*ADC_FILETER_SIZE);

adc_enable_overrun_interrupt(ADC1);

adc_enable_dma(ADC1);

ADC_CFGR1(ADC1) = (ADC_CFGR1(ADC1) & ~(0x3<<10)) | (0x1<<10);	// Hardware trigger detection on the rising edge
ADC_CFGR1(ADC1) = (ADC_CFGR1(ADC1) & ~ADC_CFGR1_EXTSEL) | (3<<ADC_CFGR1_EXTSEL_SHIFT);	// toggle by tim3

tim3_setup();

adc_start_conversion_regular(ADC1);


tim3_enable_counter(true);

delay_ms(100);

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：

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void dma1_channel1_isr(void)
{

    if ((DMA1_ISR &DMA_ISR_TCIF1) != 0) {
        DMA1_IFCR |= DMA_IFCR_CTCIF1;
    }

    tim3_enable_counter(false);

}
2.4 ADC读取
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void adc_sample(void)
{
    uint32_t sum_val1 = 0;
    uint32_t sum_val2 = 0;
    uint32_t sum_val3 = 0;
    uint32_t sum_val4 = 0;

    for(int i=0; i<ADC_FILETER_SIZE; i++){
        sum_val1 += adc_values[ADC_CHAN_CNT*i + 0];
        sum_val2 += adc_values[ADC_CHAN_CNT*i + 1];
        sum_val3 += adc_values[ADC_CHAN_CNT*i + 2];
        sum_val4 += adc_values[ADC_CHAN_CNT*i + 3];
    }

    uint32_t filter_val1 = sum_val1/ADC_FILETER_SIZE;
    uint32_t filter_val2 = sum_val2/ADC_FILETER_SIZE;
    uint32_t filter_val3 = sum_val3/ADC_FILETER_SIZE;
    uint32_t filter_val4 = sum_val4/ADC_FILETER_SIZE;

    printf("adc:%d  %d  %d  %d\r\n", filter_val1, filter_val2, filter_val3, filter_val4);

    tim3_enable_counter(true);
}

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：