蟒蛇Arduino的串行读＆安培;写 [英] python to arduino serial read & write

问题描述

我想乒乓方式来回一些Python code和Arduino的code之间。
我想两个设定点发送到Arduino code定期（例如在分），在Arduino的和放阅读;更新变量，然后从Arduino的发送状态信息回蟒蛇定期（例如在30秒）。最终，蟒蛇将发送和从MySQL数据库（后来DEV）拉动信息。

I'm trying to "ping pong" info back and forth between some python code and arduino code. I want to send two setpoints to the arduino code periodically (for instance on the minute), read them on arduino & update variables then send status info from arduino back to python periodically (such as on the :30 second). Eventually python will be sending and pulling info from a mySQL db (later dev).

现在我无法得到信息，以来回反弹可靠。我还没有发现任何接近这个在我试图修改不正常的搜索和一切。最近我已经是这样的（它实际上并不来回切换之间发送和接收）：

Right now I can't get the info to bounce back and forth reliably. I haven't found anything close to this in the searches and everything I've tried to modify isn't working. Closest I have is this (and it doesn't actually switch back and forth between send and receive):

的Python

#!/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()

Arduino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();
}

所有我最终得到重复相同的值（不是实际发送，不知道，如果它是一个字符串或字节的问题）并没有什么回python脚本。任何帮助或想法是极大的AP preciated。谢谢你。

All I end up getting is the same values repeated (not what was actually sent, not sure if its a string or byte issue) and nothing back to the python script. Any help or ideas are greatly appreciated. Thanks.

编辑：修改code到什么我目前正在运行如下建议。 Arduino是接收被Minicom验证罚款和串行通信。但是Python脚本仍然打印后空行，从Arduino的消息：

Modified code to what I'm currently running as suggested below. Arduino is receiving fine and serial communication verified by minicom. But python script still prints a blank line after "Message from arduino: ".

推荐答案

您不应该关闭串口Python中写作与阅读之间。有机会，当Arduino的响应的端口仍然关闭，在这种情况下，数据将丢失。

You shouldn't be closing the serial port in Python between writing and reading. There is a chance that the port is still closed when the Arduino responds, in which case the data will be lost.

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)

Python的 Serial.read 函数只默认返回一个字节，所以你需要或者把它在一个循环或等待要发送的数据，然后读整个缓冲区。

The Python Serial.read function only returns a single byte by default, so you need to either call it in a loop or wait for the data to be transmitted and then read the whole buffer.

在Arduino的一面，你应该考虑在没有数据可用在循环会发生什么功能。

On the Arduino side, you should consider what happens in your loop function when no data is available.

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，等候在循环函数的开始，直到数据到达：

Instead, wait at the start of the loop function until data arrives:

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

编辑2

下面就是我得到的Python从您的Arduino应用程序接口时：

Here's what I get when interfacing with your Arduino app from Python:

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

所以，这似乎是工作的罚款。

So that seems to be working fine.

在测试您的Python脚本，看来问题是，当你打开串口（至少我不乌诺）Arduino的复位，所以你需要等待几秒钟，它启动。您还只能读取的响应单行线，所以我固定的，在下面还有code：

In testing your Python script, it seems the problem is that the Arduino resets when you open the serial port (at least my Uno does), so you need to wait a few seconds for it to start up. You are also only reading a single line for the response, so I've fixed that in the code below also:

#!/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()

下面是上面的输出现在：

Here's the output of the above now:

$ 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

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