Question

我正在用Python编写代码，通过串口与超声波测距仪进行通信，以执行以下操作：
- 每0.1秒，向传感器发送一个命令进行距离测量，并记录传感器的响应
- 显示最近5秒内所有距离测量值的图表

这是我的代码：

import serial
import numpy as np
import time
from matplotlib import pyplot as plt

tagnr=2#Tag number of the sensor that we're pinging  
samplingRate=.1#Sampling Rate in seconds  
graphbuf=50.#Buffer length in samples of logger graph  

!#Initialize logger graph  
gdists=np.zeros(graphbuf)  
ax1=plt.axes()  

!#Main loop  
nsr=time.time()#Next sample request  
try:  
    while True:  
        statreq(tagnr)#Send status request to sensor over serial port  
        temp,dist=statread(tagnr)#Read reply from sensor over serial port  
        gdists=np.concatenate((gdists[1:],np.array([dist])))  
        print gdists  
        nsr=nsr+samplingRate  
        while time.time()<nsr:  
            pass  

finally:  
    ser.close()#Close serial port  
    print 'Serial port closed.'

现在，我的代码可以获取最近50次测量的数组，但我不知道如何在图形中同时显示这些（我通常使用Matplotlib绘制我的图形）。我应该使用线程吗？或者使用pyGTK或pyQt4使用动画图？我还在考虑使用pygame？我的计时机制也不是很优，但我认为它非常准确。

Answer 1

matplotlib有动画图，可以在显示图表时更新数据：take a look at this page。

您的代码可能如下所示：

import serial
import numpy as np
import time
from matplotlib import pyplot as plt

plt.ion() # set plot to animated

tagnr=2#Tag number of the sensor that we're pinging  
samplingRate=.1#Sampling Rate in seconds  
graphbuf=50.#Buffer length in samples of logger graph  

!#Initialize logger graph  
gdists=np.zeros(graphbuf)  
ax1=plt.axes()  

# make plot
line, = plt.plot(gdists)

!#Main loop  
nsr=time.time()#Next sample request  
try:  
    while True:  
        statreq(tagnr)#Send status request to sensor over serial port  
        temp,dist=statread(tagnr)#Read reply from sensor over serial port  
        gdists=np.concatenate((gdists[1:],np.array([dist])))  
        print gdists

        line.set_ydata(gdists)  # update the data
        plt.draw() # update the plot

        nsr=nsr+samplingRate  
        while time.time()<nsr:  
            pass  

finally:  
    ser.close()#Close serial port  
    print 'Serial port closed.'

只是一些建议（可能不好）：我个人会以一种释放某些处理器而不会失去准确性的方式使用time.sleep。我还会在try / except块上添加一些错误类型。我认为np.roll比concatenate更好/更快。

使用python和matplotlib同时获取数据并更新图形

1 个答案: