> For the complete documentation index, see [llms.txt](https://docs.petoi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.petoi.com/chinese/biboard/li-cheng/mo-ni-shu-zi-zhuan-huan-qi.md).

# 3. 模拟-数字转换器

BiBoard（ESP32）可变增益ADC的应用

BiBoard ADC使用说明

ESP32模块34，35，36和39脚仅支持输入，在BiBoard上我们将其配置成模拟输入端口，方便开发者们连接4个足底传感器。

BiBoard模拟输入模-数转换器（ADC）的用法和基础的Arduino UNO相同，但是精度更高（12位，UNO为10位），同时增加了可编程增益放大器，可以让ADC工作在最佳的范围内。

当输入1V电压信号时，如果按照普通配置为12bit访问，参考电压等于电源电压（3.3V）：对应的输出为0～1241，ADC很大一部分量程会被浪费掉，造成数据不精确。当我们配置成可编程增益的时候，就可以让1V的输入信号填满几乎整个ADC量程，精度和分辨率大大提高。

我们的例程使用4个输入，分别配置成：0/2.5/6/11分贝的放大增益，需要注意的是ESP32 Arduino默认配置的是11分贝的放大增益。

我们使用“analogSetPinAttenuation(PIN\_NAME, attenuation)”来配置单个输入引脚的增益，也可以使用“analogSetAttenuation(attenuation)”来配置全部模拟输入引脚的增益。

```
// Ain 34 - 0dB Gain - ADC_0db
analogSetPinAttenuation(34, ADC_0db);

// Ain 35 - 2.5dB Gain - ADC_2_5db
analogSetPinAttenuation(35, ADC_2_5db);

// Ain 36 - 6dB Gain - ADC_6db
analogSetPinAttenuation(36, ADC_6db);

// Ain 39 - 11dB Gain - ADC_11db    (default)
analogSetPinAttenuation(39, ADC_11db);
```

实际测试，当输入1V标准电压时，ADC的数值分别为：3850/2890/2025/1050。在今后的制作中，可以通过改变ADC的增益改变ADC的量程，而不需要麻烦的更换基准电压源了。


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