虚谷号和Arduino的自定义通讯
============================================

原理简介
----------------------

虚谷号和板载Arduino的通讯，是通过串口来实现的。xugu库也是基于Firmata协议开发，跑在串口协议上。

应用场景
---------------------

xugu库支持的传感器主要分为两类，一是开关量（也称数字）传感器，返回高低电平；二是模拟传感器，返回0-5V之间的电压。

除了这两类的传感器，还有数字型传感器，如DH11温湿度传感器，DS18B20温度传感器。这些传感器无法使用xugu库，如果项目中用到这类传感器，就需要另写代码，自定义通讯协议。


范例：DH11传感器实验
-----------------------------

Arduino接DH11传感器，将数据通过串口发送给虚谷号。虚谷号使用Python代码，将串口信息打印出来。


1.Arduino代码

::


    // Example testing sketch for various DHT humidity/temperature sensors
    // Written by ladyada, public domain

    #include "DHT.h"
    #define DHTPIN 13     // what pin we're connected to

    // Uncomment whatever type you're using!
    #define DHTTYPE DHT11   // DHT 11 
    //#define DHTTYPE DHT22   // DHT 22  (AM2302)
    //#define DHTTYPE DHT21   // DHT 21 (AM2301)

    // Connect pin 1 (on the left) of the sensor to +5V
    // Connect pin 2 of the sensor to whatever your DHTPIN is
    // Connect pin 4 (on the right) of the sensor to GROUND
    // Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

    DHT dht(DHTPIN, DHTTYPE);

    void setup() {
      Serial.begin(115200); 
    }

    void loop() {
      // Reading temperature or humidity takes about 250 milliseconds!
      // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
      //String cmd=serial_command();

      String cmd="";
      while(1){
        if(Serial.available()){
          cmd+=char(Serial.read());
          delay(2);

        }else{break;}  
      }
      cmd.replace("\n","");
      cmd.replace("\0","");
      if(cmd=="PING"){
      Serial.print("OK");
      }
      //delay(2000);
      float h = dht.readHumidity();
      float t = dht.readTemperature();

      //lcd.clear();
      // check if returns are valid, if they are NaN (not a number) then something went wrong!
      if (isnan(t) || isnan(h)) {
        Serial.println("Failed to read from DHT");
      } else {
        Serial.print(h);
        Serial.print(t);
      }
      delay(150);
    }


2.Python代码

::


    import serial
    import time
    import subprocess
    import os

    arduino_serial=serial.Serial('/dev/ttyS1',115200)
    arduino_serial.close()
    time.sleep(0.5)
    arduino_serial.open()
    time.sleep(0.5)

    def arduino_burn():
            """
            :return:
            """
            subprocess.call("arduino_burn.sh /home/scope/Desktop/DHT11/DHT11.ino /home/scope/software/log/arduino_burn_log.txt", shell=True)

    def serial_send(msg):
        global arduino_serial
        msg=msg.encode("utf-8")
        arduino_serial.write(msg)
        time.sleep(0.01)

    def serial_receive(pin_num = '1'):
        global arduino_serial
        receiver=arduino_serial.read_all()
        if receiver:
            if b'\0' not in receiver:
                receiver=receiver.decode("utf-8")
                if '\r\n' in receiver:
                    receiver = receiver.replace('\r\n', '')
                return receiver
        else:
            return -1

    def check_protocol():
        serial_send("PING")
        time.sleep(1)
        receiver=serial_receive()
        if("OK" not in str(receiver)):
            print("not found firmata protocol, burn it.")
            arduino_burn()
            print("burn complete")

    def getTempandHum():
        """
        读取温度和湿度
        """
        value = serial_receive()
        if value != -1:
            humi = value[:5]
            Temp = value[-5:]
            print("温度:%s 湿度:%s%%"%(Temp,humi))

    check_protocol()
    while True: #创建一个循环
        getTempandHum()
        time.sleep(1)


高级技巧
------------------

在Python代码中自动检测Arduino，并调用烧写工具。

参考范例：灯带控制
---------------------------



::


    import serial
    import time
    import subprocess
    import os

    arduino_serial=serial.Serial('/dev/ttyS1',9600)
    arduino_serial.close()
    time.sleep(0.5)
    arduino_serial.open()
    time.sleep(0.5)

    def arduino_burn():
        """

        :return:
        """
        path=os.getcwd()
        subprocess.call("arduino_burn.sh /home/scope/Desktop/Neo_xugu_test/Arduino_NeoPixel/Arduino_NeoPixel.ino /home/scope/software/log/arduino_burn_log.txt", shell=True)

    def serial_send(msg):
        global arduino_serial
        msg=msg.encode("utf-8")
        print(msg)
        arduino_serial.write(msg)

    def serial_receive():
        global arduino_serial
        receiver=arduino_serial.read_all()
        receiver=receiver.decode("utf-8")
        return receiver

    def check_protocol():
        serial_send("PING")
        time.sleep(1)
        receiver=serial_receive()
        if(receiver!="OK"):
            print("not found firmata protocol, burn it.")
            arduino_burn()
            print("burn complete")

    def set_pixel(index,r,g,b):
        index=str(index)
        r=str(r)
        g=str(g)
        b=str(b)
        cmd="N"+index+"R"+r+"G"+g+"B"+b+";"
        serial_send(cmd)

    check_protocol()

    while True:
        a=0
        while a <8:
            for i in range(8):
                if i==a:
                    set_pixel(i,200,200,0)
                else:
                    set_pixel(i,0,0,0,)
            time.sleep(1)
            a+=1


    if(__name__=="__main__"):
        print("please import this file to python program")