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I am showing real time plot from Arduino sensors with matplotlib and Python 3.9.13.

I encounter a problem which is: The pyplot window keeps opening a new one everytime a new data is obtained from the Arduino' sensor, instead of refreshing on the current pyplot window.

How to fix it?

If I try to close one of the old pyplot window all pyplot windows will be closed, which is troublesome.

g

This is my code :

import serial 
import numpy as np
import pandas as pd 
import matplotlib.pyplot as plt 
from drawnow import *

tempC=[]
altitude=[]
PPMCO2=[]
MQ7CO=[]

arduinoData = serial.Serial('/dev/ttyACM0', 115200) 
plt.ion() 
cnt=0

def makeFig(): 
    fig, axs = plt.subplots(2,2)
    (ax1, ax2), (ax3, ax4) = axs                            
    ax1.grid(True)                                      
    ax1.plot(PPMCO2, 'ro-', label='CO2 (from MQ135)')    
    ax1.legend(loc='upper left')                    
                                                 
    ax2.grid(True)  
    ax2.plot(MQ7CO, 'g*-', label='CO (from MQ7)')                  
    ax2.ticklabel_format(useOffset=False)         
    ax2.legend(loc='upper right')       
          
    ax3.grid(True)  
    ax3.plot(tempC, 'mp-', label='Degrees C')                  
    ax3.ticklabel_format(useOffset=False)         
    ax3.legend(loc='upper right') 

    ax4.grid(True)  
    ax4.plot(altitude, 'kD-', label='Altitude (m)')                  
    ax4.ticklabel_format(useOffset=False)         
    ax4.legend(loc='upper right') 

while True: 
    while (arduinoData.inWaiting()==0): 
        pass 
    arduinoString = arduinoData.readline()
    #print(arduinoString)   
    s = str(arduinoString)
    s = s.replace('b\'','')
    s = s.replace('\\r\\n\'','')
    f = str(arduinoString)
    f = f.replace('b\'','[')
    f = f.replace('\\r\\n\'','],')
    print(s) 
    print(f)     
    dataArray = s.split(',')
    temp = float(dataArray[0])            
    alt = float(dataArray[1])  
    co2 = float(dataArray[2])            
    co = float(dataArray[3]) 
    tempC.append(temp)            
    altitude.append(alt)                
    PPMCO2.append(co2)            
    MQ7CO.append(co)                
    drawnow(makeFig)                      
    plt.pause(.000001)     
    cnt=cnt+1
    
if(cnt>50):
    tempC.pop(0)
    altitude.pop(0)
    PPMCO2.pop(0)
    MQ7CO.pop(0)
DS Glanzsche
  • 1
  • 1
    Does this answer your question? [Dynamically updating Matplotlib](https://stackoverflow.com/questions/69186418/dynamically-updating-matplotlib) – Björn Mar 17 '23 at 20:37
  • Drawnow keeps calling `fig, axs = plt.subplots()`. Do that outside the loop – Jody Klymak Mar 22 '23 at 21:46
  • @Björn, no I tried that and still not working now – DS Glanzsche Mar 25 '23 at 14:22
  • @JodyKlymak, if I put `drawnow(makeFig) ` out of the while loop, the plot does not even showing at all – DS Glanzsche Mar 25 '23 at 14:23
  • ?? I didn’t say to put the draw outside the loop. I said to stop creating new figures inside the loop. – Jody Klymak Mar 25 '23 at 14:48
  • I put `fig, axs = plt.subplots(2,2)` before `def makeFig(): ` it only show 1 window, but now the problem is the screen is blank and not showing the plot. I believe this is because I use 4 subplots. – DS Glanzsche Mar 27 '23 at 05:29

0 Answers0