pyserial - 如何阅读从串行设备发送的最后一行 [英] pyserial - How to read the last line sent from a serial device

问题描述

我有一个Arduino连接到我的计算机上运行一个循环，发送通过串行端口值回计算机每100＆NBSP;毫秒。

我想打一个Python脚本，它将从串口只每隔几秒钟看，所以我希望它只是看到从阿尔杜伊诺发送的最后一件事。

如何在Pyserial这样做吗？

这里的code我试图简化版，它的工作。它顺序读取行。

 导入序列
进口时间SER = serial.Serial（'COM4，9600，超时= 1）
而1：
    time.sleep（10）
    打印ser.readline（）＃如何我从设备发送的最新行？
 

解决方案

也许我误解你的问题，但因为它是一个串口线，你必须阅读一切从Arduino的顺序发送的 - 它会被缓存起来Arduino的，直到你读它。

如果你想有一个状态显示，显示发送最新的东西 - 使用的集成了code在你的问题一个线程（减去睡眠），并保持阅读从最新的行的最后一个完整产品线Arduino的。

更新： mtasic 的例子code是相当不错的，但如果阿尔杜伊诺派出了部分行，当 inWaiting（）被调用时，你会得到一个截断线。相反，你想要做的就是把最后的完整的行成 last_received ，并保持在局部线缓冲，以便它可以被附加到下一次轮循环。事情是这样的：

 高清接收（SER）：
    全球last_received    buffer_string =''
    而真正的：
        buffer_string = buffer_string + ser.read（ser.inWaiting（））
        如果的'\\ n'在buffer_string：
            线= buffer_string.split（'\\ n'）＃保证至少有2项
            last_received =行[-2]
            ＃如果Arduino的发送的空行地段，你会失去
            #last填充线，所以你可以作上述表示的条件
            #like这样：如果线[-2]：last_received =行[-2]
            buffer_string =行[-1]
 

关于使用的ReadLine（）的：这是什么Pyserial文档有说（略编辑的清晰度和附带一提改成readlines（））：

  

使用的ReadLine时要小心。做
  打开时指定超时
  串行端口，否则它可以阻止
  永远如果没有换行符
  好评。还注意到，readlines方法（）
  仅适用于超时。它
  取决于有超时和
  除$ P $其中pts，作为EOF（文件结束）。

这似乎是很有道理的我！

I have an Arduino connected to my computer running a loop, sending a value over the serial port back to the computer every 100 ms.

I want to make a Python script that will read from the serial port only every few seconds, so I want it to just see the last thing sent from the Arduino.

How do you do this in Pyserial?

Here's the code I tried which does't work. It reads the lines sequentially.

import serial
import time

ser = serial.Serial('com4',9600,timeout=1)
while 1:
    time.sleep(10)
    print ser.readline() #How do I get the most recent line sent from the device?

解决方案

Perhaps I'm misunderstanding your question, but as it's a serial line, you'll have to read everything sent from the Arduino sequentially - it'll be buffered up in the Arduino until you read it.

If you want to have a status display which shows the latest thing sent - use a thread which incorporates the code in your question (minus the sleep), and keep the last complete line read as the latest line from the Arduino.

Update: mtasic's example code is quite good, but if the Arduino has sent a partial line when inWaiting() is called, you'll get a truncated line. Instead, what you want to do is to put the last complete line into last_received, and keep the partial line in buffer so that it can be appended to the next time round the loop. Something like this:

def receiving(ser):
    global last_received

    buffer_string = ''
    while True:
        buffer_string = buffer_string + ser.read(ser.inWaiting())
        if '\n' in buffer_string:
            lines = buffer_string.split('\n') # Guaranteed to have at least 2 entries
            last_received = lines[-2]
            #If the Arduino sends lots of empty lines, you'll lose the
            #last filled line, so you could make the above statement conditional
            #like so: if lines[-2]: last_received = lines[-2]
            buffer_string = lines[-1]

Regarding use of readline(): Here's what the Pyserial documentation has to say (slightly edited for clarity and with a mention to readlines()):

Be careful when using "readline". Do specify a timeout when opening the serial port, otherwise it could block forever if no newline character is received. Also note that "readlines()" only works with a timeout. It depends on having a timeout and interprets that as EOF (end of file).

which seems quite reasonable to me!

这篇关于pyserial - 如何阅读从串行设备发送的最后一行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！