112 lines
3.3 KiB
Markdown
112 lines
3.3 KiB
Markdown
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# BearPi-HM_Nano开发板传感器驱动开发——MQ2读取烟雾浓度
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本示例将演示如何在BearPi-HM_Nano开发板上使用E53_SF1读取烟雾浓度，当烟雾浓度超标时蜂鸣器发出警报，设备安装如下图所示。
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## E53_SF1 API分析
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本案例主要使用了以下API完成烟雾浓度读取。
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### E53SF1Init()
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```C
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void E53SF1Init(void)
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```
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**描述：**
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初始化E53_SF1。
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### MQ2PPMCalibration()
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```C
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void MQ2PPMCalibration(void)
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```
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**描述：**
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MQ2传感器校准。
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### GetMQ2PPM()
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```C
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float GetMQ2PPM(void)
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```
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**描述：**
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获取烟雾浓度ppm。
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## 硬件设计
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本案例将用到 E53_SF1 智慧烟感扩展板与 BearPi-HM_Nano 开发板，其中E53_SF1扩展板原理图如下，ADC输出引脚为第五脚，将E53_SF1扩展板插在 BearPi-HM_Nano 开发板上后，该ADC输出引脚与GPIO_13相连接，通过查看芯片手册可知GPIO_13对应的是 ADC Channel 6 ,所以需要编写软件去读取ADC Channel 6的电压实现对烟雾浓度的读取。
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E53_SF1 智慧烟感扩展板与 BearPi-HM_Nano 开发板安装如下图所示。
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## 软件设计
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**主要代码分析**
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首先调用 `E53SF1Init()` 函数初始化E53_SF1所接的引脚的功能，再等待1s后进行校准，获取正常环境下传感器的参数，然后循环调用 `GetMQ2PPM()` 函数读取ppm值并通过串口打印出来，当ppm大于100时触发蜂鸣器报警，小于100时关闭报警。
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```C
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static void ExampleTask(void)
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{
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int ret;
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float ppm;
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E53SF1Init();
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//Sensor calibration
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usleep(1000000);
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MQ2PPMCalibration();
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while (1) {
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printf("=======================================\r\n");
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printf("*************E53_SF1_example***********\r\n");
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printf("=======================================\r\n");
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//get mq2 ppm
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ret = GetMQ2PPM(&ppm);
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if (ret != 0) {
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printf("ADC Read Fail\n");
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return ;
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}
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printf("ppm:%.3f \n", ppm);
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if (ppm > 15) {
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BeepStatusSet(ON);
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} else {
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BeepStatusSet(OFF);
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}
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usleep(1000000);
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}
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}
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```
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## 编译调试
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### 修改 BUILD.gn 文件
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修改`device\bearpi\bearpi_hm_nano\app`路径下 BUILD.gn 文件，指定 `e53_sf1_example` 参与编译。
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```r
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"C1_e53_sf1_mq2:e53_sf1_example",
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#"C2_e53_ia1_temp_humi_pls:e53_ia1_example",
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#"C3_e53_sc1_pls:e53_sc1_example",
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#"C4_e53_sc2_axis:e53_sc2_example",
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#"C5_e53_is1_infrared:e53_is1_example",
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```
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### 运行结果
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示例代码编译烧录代码后，按下开发板的RESET按键，通过串口助手查看日志，会打印以下信息，对着烟雾探头制作烟雾，ppm会升高蜂鸣器发出报警。
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```c
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=======================================
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*************E53_SF1_example***********
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=======================================
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ppm:19.094
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=======================================
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*************E53_SF1_example***********
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=======================================
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ppm:18.797
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```
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