无法将字符串从 python 发送到 arduino

Question

所以我想创建一个简单的程序，让我可以用我的电脑控制 RGB LED 的颜色。我在 python 3 上用 tkinter 创建了一个 window 来控制颜色，但问题是当我尝试更改颜色时它根本没有响应。我不知道发生了什么。我试图将字符串放入 arduino 代码中并且成功了，但是当我通过串行通信发送时它根本没有响应。

Arduino 代码

//pin layout
int   red = 12;
int green = 11;
int  blue = 10;

//string that will receive
String    data;
String subData;

//Color values
int value[3];

void setup() {
  Serial.begin(9600);
  pinMode(red,OUTPUT);
  pinMode(green,OUTPUT);
  pinMode(blue,OUTPUT);  
  }

void loop() {
  while(Serial.available() == 0);
    data = Serial.readString();

    int initialVal =0;
    int val;

    int pos = 0;

    do{
    val = data.indexOf(',',initialVal);
    subData = data.substring(initialVal,val);
    value[pos] = subData.toInt();
    pos = pos + 1;
    initialVal = val + 1;
    }while(val != -1);
    Serial.println(data);
    analogWrite(red,value[0]);
    analogWrite(green,value[1]);
    analogWrite(blue,value[2]);  


  }

这里是 python 代码：

from tkinter import *
from serial import *


window = Tk()
#all definitions for the window
window.title("RGB LED control Panel")
window.geometry("300x180")
window.resizable(False,False)

Title = Label(window, text = "RGB control", width = 15)
Title.grid(row = 0, column = 0, columnspan = 3)

Explanation = Label(window, text = "  This window controls the \ncolor of an RGB LED. Have \n fun!!!")
Explanation.grid(row =1 , column = 3)

RedTitle = Label(window, text = "Red", width = 5, bg = "Red")
RedTitle.grid(row = 1, column = 0)

GreenTitle = Label(window, text = "Green", width = 5, bg = "Green")
GreenTitle.grid(row = 1, column = 1)

BlueTitle = Label(window, text = "Blue", width = 5, bg = "Blue")
BlueTitle.grid(row = 1, column = 2)


RedScale = Scale(window, from_ = 0, to = 255, orient = VERTICAL)
RedScale.grid(row = 2, column = 0)

GreenScale = Scale(window, from_ = 0, to = 255, orient = VERTICAL)
GreenScale.grid(row = 2, column = 1)

BlueScale = Scale(window, from_ = 0, to = 255, orient = VERTICAL)
BlueScale.grid(row = 2, column = 2)

#now the serial com with the arduino

arduino = Serial()
arduino.baudrate = 9600
arduino.port = "COM3"
arduino.open()

while 1:
    window.update_idletasks()
    window.update()

    RED = str(RedScale.get())
    GREEN = str(GreenScale.get())
    BLUE = str(BlueScale.get())

    finalString = RED + "," + GREEN + "," + BLUE

    arduino.write(finalString.encode("utf-8"))
    print(finalString)
    print("\n")

更新

因此为此更改 arduino 代码（在接收字符串的部分）：

  while(Serial.available() == 0);
  data = Serial.readStringUntil('\n');
  Serial.setTimeout(0.01);

以及 python 代码中将字符串发送至此的部分：而 1： window.update_idletasks() window.update()

    RED = str(RedScale.get())
    GREEN = str(GreenScale.get())
    BLUE = str(BlueScale.get())

    finalString = RED + "," + GREEN + "," + BLUE + "\n"
    if lastMsg != finalString:
        finalString= finalString.encode("utf-8")
        arduino.write(finalString)
        lastMsg = finalString

    print(finalString)

LED 会改变它的颜色，但它有时会变成其他颜色并且 python 程序会崩溃！！！！ Serial.readStringUntil("\n") 或 arduino.write(finalString) 中是否缺少任何内容？

Answer 1

你只是太多一条又一条消息发送到 Arduino，所以当它调用 readString() 它需要很长的 string，并且递增 pos 超过合法间隔 0..2，这意味着你正在破坏memory stack 从那里任何事情都有可能发生。

建议的修复：

将Serial.readString()替换为Serial.readStringUntil('\n')，formerreturns超时，而后者 returns 当它匹配 换行符 字符或它超时。默认超时为1秒。

改变

finalString = RED + "," + GREEN + "," + BLUE

至

finalString = RED + "," + GREEN + "," + BLUE + "\n"

并删除 print("\n")

更改您的 python 代码，使其仅在消息内容 发生更改时才向 Arduino 发送消息 wrt。发送的最后一个：

last_msg = ""
while 1:
    window.update_idletasks()
    window.update()

    RED = str(RedScale.get())
    GREEN = str(GreenScale.get())
    BLUE = str(BlueScale.get())

    finalString = RED + "," + GREEN + "," + BLUE + "\n"

    if finalString != last_msg:
        arduino.write(finalString.encode("utf-8"))
        last_msg = finalString

        print(finalString)

注意 01： 即使在您修复它之后，考虑将您的 Arduino 代码发布到 code review 以获取关于 代码样式和强大的设计。

注意 02： 即使有建议的修复，源代码 仍然易受攻击 错误的行为在正确的情况下（例如：如果readStringUntil()在\n匹配之前超时会发生什么？你如何处理部分输入?)

编辑 1: python 代码 崩溃是因为您没有检查对象的有效性RedScale、GreenScale 和 BlueScale 在使用 get() 访问它们之前，这显然在 tk 之后立即失败window 已关闭.

一个天真的解决方案如下：

import sys
import time

global exitFlag
exitFlag = False

...

def endProgram():
    global exitFlag
    exitFlag = True
    window.destroy()

window.protocol("WM_DELETE_WINDOW", endProgram)

...

last_msg = ""
finalString = ""
while 1:
    if not exitFlag:
        window.update_idletasks()

    if not exitFlag:
        window.update()

    if not exitFlag:
        RED = str(RedScale.get())
        GREEN = str(GreenScale.get())
        BLUE = str(BlueScale.get())

        finalString = RED + "," + GREEN + "," + BLUE + "\n"

    if finalString != last_msg:
        arduino.write(finalString.encode("utf-8"))
        last_msg = finalString

        print(finalString)

     if exitFlag:
         sys.exit()

请注意，尽管 Whosebug 人满为患 人们建议使用此解决方案，但我认为这是 糟糕的设计 我怀疑仍然 有问题 。一个合适的解决方案是 override event listener 以调整 Scale 实例，这样Scale 的值仅在用户实际更改时才被读取和发送。我会让你算出细节。

无法将字符串从 python 发送到 arduino

can't send string from python to arduino

python

string

tkinter

arduino

pyserial