10 rtthread studio adc三通道采集ntc电阻出现问题

发布于 2021-09-04 13:36:22 浏览：1936 订阅该版

是这样配置的 三个通道采集三个ntc热敏电阻的值 比单个通道采集一个热敏电阻时 温度要低1度左右

```c
#include "temp_adc.h"

#define ADC_DEV_NAME        "adc1"      /* ADC 设备名称 */
#define ADC_DEV_CHANNEL_PA3     3           /* ADC 通道 */
#define ADC_DEV_CHANNEL_PA4     4           /* ADC 通道 */
#define ADC_DEV_CHANNEL_PA5     5           /* ADC 通道 */
#define REFER_VOLTAGE       330         /* 参考电压 3.3V,数据精度乘以100保留2位小数*/
#define CONVERT_BITS        (1 << 12)   /* 转换位数为12位 */

rt_adc_device_t adc_dev;

/**中位值平均滤波法
 * （1）原理:采一组队列去掉最大值和最小值
 * （2）特点:优点：融合了两种滤波的优点。对于偶然出现的脉冲性干扰，可消除有其引起的采样值偏差，对周期干扰有良好的抑制作用，平滑度高，适于高频振荡的系统；
                           缺点：测量速度慢；
 * */
#define N 8

static rt_uint32_t filter(rt_uint32_t ADC_DEV_CHANNEL) {
    rt_uint8_t i = 0, j = 0;
    rt_uint32_t value_buf[N];
    rt_uint32_t temp = 0,sum = 0;

for(i = 0; i < N; i++){
        value_buf[i] = rt_adc_read(adc_dev, ADC_DEV_CHANNEL);
        rt_thread_delay(5);
    }

for(j = 0; j < N - 1; j++) {
        for(i = 0; i < N - j; i++) {
            if(value_buf[i] > value_buf[i + 1]) {
                temp = value_buf[i];
                value_buf[i] = value_buf[i + 1];
                value_buf[i + 1] = temp;
            }
        }
    }
    for(i = 1; i < N - 1; i++) {
        sum += value_buf[i];
    }
    return (rt_uint32_t)(sum / (N - 2));
}
/***********************************end***********************************/

//电压换算成温度
static float temp_data(rt_uint32_t ADC_DEV_CHANNEL)
{
   float Rt=0;
   float Rp=10;
   float T2=273.15+25;
   float Bx=3435;
   float Ka=273.15;
   rt_uint32_t value=0;
   float temp=0,vol;

/* 读取采样值 */
   value = filter(ADC_DEV_CHANNEL);
//   rt_kprintf("ADC:%d \n", value);
   /* 转换为对应电压值 */
   vol = (float)value * REFER_VOLTAGE / CONVERT_BITS;
//   rt_kprintf("the voltage is :%d.%02dV \n", (int)vol / 100, (int)vol % 100);
   Rt = vol * 10 / (REFER_VOLTAGE-vol);//求出当前温度阻值 (BaseVoltage-RV)/R16=RV/RT;
//   rt_kprintf("Rt :%d \n", (int)(Rt * 10000));
   temp = 1 / (1 / T2 + (log(Rt / Rp) / Bx)) - Ka;//%RT = RN exp*B(1/T-1/TN)%
//   rt_kprintf("temp :%d.%02dC \n", (int)(temp * 100) / 100,(int)(temp * 100) % 100);
   return temp;
}

static float adc_vol(rt_uint32_t ADC_DEV_CHANNEL,float *temp)
{
    rt_err_t ret = RT_EOK;
    /* 查找设备 */
    adc_dev = (rt_adc_device_t)rt_device_find(ADC_DEV_NAME);
    if (adc_dev == RT_NULL)
    {
        rt_kprintf("adc sample run failed! can't find %s device!\n", ADC_DEV_NAME);
        return RT_ERROR;
    }

/* 使能设备 */
    ret = rt_adc_enable(adc_dev, ADC_DEV_CHANNEL);

*temp = temp_data(ADC_DEV_CHANNEL);

/* 关闭通道 */
    ret = rt_adc_disable(adc_dev, ADC_DEV_CHANNEL);

return ret;
}
```
```c
static void temp_get_entry(void *parameter)
{
    while(1)
    {
        float temp3=0,temp4=0,temp5=0,temp=0;
        adc_vol(ADC_DEV_CHANNEL_PA3,&temp3);
        rt_thread_delay(10);
        adc_vol(ADC_DEV_CHANNEL_PA4,&temp4);
        rt_thread_delay(10);
        adc_vol(ADC_DEV_CHANNEL_PA5,&temp5);
        rt_thread_delay(10);
        temp = (temp3 + temp4 + temp5)/3;
        rt_kprintf("temp :%dC    %dC    %dC    temp:%dC\n", (int)(temp3 * 100),(int)(temp4 * 100),(int)(temp5 * 100),(int)(temp * 100));
    }

}

rt_thread_t temp_get_adc=RT_NULL;
int temp_get_adc_init(void)
{
    //创建显示线程 优先级设置为31
    temp_get_adc = rt_thread_create("temp_get_adc", temp_get_entry, RT_NULL, 2048, 8, 20);
    //启动显示线程
    if(RT_NULL != temp_get_adc)
    {
        rt_thread_startup(temp_get_adc);
//        rt_kprintf("display_ok\n");
    }
    return 0;
}
```