python至arduino串行读写

Question

我正在尝试在某些python代码和arduino代码之间来回“乒乓”信息。我想定期向arduino代码发送两个设定值（例如在分钟上），在arduino上读取它们并更新变量，然后定期（例如在30秒内）将状态信息从arduino发送回python。最终，python将从mySQL数据库发送信息并从中提取信息（后来的开发）。

现在，我无法获得可靠往返的信息。我没有在搜索中找到与此相近的任何内容，而且我尝试修改的所有内容均无效。我最近的是这个（它实际上并没有在发送和接收之间来回切换）：

蟒蛇

#!/usr/bin/python
import serial
import syslog
import time

#The following line is for serial over GPIO
port = '/dev/ttyS0'


ard = serial.Serial(port,9600,timeout=5)

i = 0

while (i < 4):
    # Serial write section

    setTempCar1 = 63
    setTempCar2 = 37
    ard.flush()
    setTemp1 = str(setTempCar1)
    setTemp2 = str(setTempCar2)
    print ("Python value sent: ")
    print (setTemp1)
    ard.write(setTemp1)
    time.sleep(4)

    # Serial read section
    msg = ard.readline()
    print ("Message from arduino: ")
    print (msg)
    i = i + 1
else:
    print "Exiting"
exit()

的Arduino：

// Serial test script

int setPoint = 55;
String readString;

void setup()
{

  Serial.begin(9600);  // initialize serial communications at 9600 bps

}

void loop()
{
  while(!Serial.available()) {}
  // serial read section
  while (Serial.available())
  {
    if (Serial.available() >0)
    {
      char c = Serial.read();  //gets one byte from serial buffer
      readString += c; //makes the string readString
    }
  }

  if (readString.length() >0)
  {
    Serial.print("Arduino received: ");  
    Serial.println(readString); //see what was received
  }

  delay(500);

  // serial write section

  char ard_sends = '1';
  Serial.print("Arduino sends: ");
  Serial.println(ard_sends);
  Serial.print("\n");
  Serial.flush();
}

我最终得到的是重复的相同值（不是实际发送的值，不确定是字符串还是字节问题），什么也没有返回到python脚本。任何帮助或想法，我们将不胜感激。谢谢。

编辑：修改代码为我当前正在运行，如下所示。Arduino正在接受minicom验证的精细和串行通信。但是python脚本在“来自arduino的消息：”之后仍然打印空白行。

Answer 1

在写和读之间，您不应该关闭Python中的串行端口。Arduino响应时，端口仍有可能关闭，在这种情况下，数据将丢失。

while running:  
    # Serial write section
    setTempCar1 = 63
    setTempCar2 = 37
    setTemp1 = str(setTempCar1)
    setTemp2 = str(setTempCar2)
    print ("Python value sent: ")
    print (setTemp1)
    ard.write(setTemp1)
    time.sleep(6) # with the port open, the response will be buffered 
                  # so wait a bit longer for response here

    # Serial read section
    msg = ard.read(ard.inWaiting()) # read everything in the input buffer
    print ("Message from arduino: ")
    print (msg)

PythonSerial.read函数默认情况下仅返回一个字节，因此您需要在循环中调用它或等待数据传输然后读取整个缓冲区。

在Arduino方面，您应该考虑loop没有可用数据时函数中会发生什么。

void loop()
{
  // serial read section
  while (Serial.available()) // this will be skipped if no data present, leading to
                             // the code sitting in the delay function below
  {
    delay(30);  //delay to allow buffer to fill 
    if (Serial.available() >0)
    {
      char c = Serial.read();  //gets one byte from serial buffer
      readString += c; //makes the string readString
    }
  }

相反，请等待loop函数开始直到数据到达：

void loop()
{
  while (!Serial.available()) {} // wait for data to arrive
  // serial read section
  while (Serial.available())
  {
    // continue as before

编辑2

这是从Python与您的Arduino应用进行交互时得到的结果：

>>> import serial
>>> s = serial.Serial('/dev/tty.usbmodem1411', 9600, timeout=5)
>>> s.write('2')
1
>>> s.readline()
'Arduino received: 2\r\n'

因此，这似乎很好。

在测试您的Python脚本时，似乎问题在于打开串口时Arduino会重置（至少我的Uno会这样做），因此需要等待几秒钟才能启动。您还只读取了一行响应，因此我也在下面的代码中修复了该问题：

#!/usr/bin/python
import serial
import syslog
import time

#The following line is for serial over GPIO
port = '/dev/tty.usbmodem1411' # note I'm using Mac OS-X


ard = serial.Serial(port,9600,timeout=5)
time.sleep(2) # wait for Arduino

i = 0

while (i < 4):
    # Serial write section

    setTempCar1 = 63
    setTempCar2 = 37
    ard.flush()
    setTemp1 = str(setTempCar1)
    setTemp2 = str(setTempCar2)
    print ("Python value sent: ")
    print (setTemp1)
    ard.write(setTemp1)
    time.sleep(1) # I shortened this to match the new value in your Arduino code

    # Serial read section
    msg = ard.read(ard.inWaiting()) # read all characters in buffer
    print ("Message from arduino: ")
    print (msg)
    i = i + 1
else:
    print "Exiting"
exit()

现在是上面的输出：

$ python ardser.py
Python value sent:
63
Message from arduino:
Arduino received: 63
Arduino sends: 1


Python value sent:
63
Message from arduino:
Arduino received: 63
Arduino sends: 1


Python value sent:
63
Message from arduino:
Arduino received: 63
Arduino sends: 1


Python value sent:
63
Message from arduino:
Arduino received: 63
Arduino sends: 1


Exiting