Display analog data from Arduino using Python (matplotlib animation)

ldr.py

"""
ldr.py

Display analog data from Arduino using Python (matplotlib)

Author: Mahesh Venkitachalam
Website: electronut.in
"""

import sys, serial, argparse
import numpy as np
from time import sleep
from collections import deque

import matplotlib.pyplot as plt 
import matplotlib.animation as animation

    
# plot class
class AnalogPlot:
  # constr
  def __init__(self, strPort, maxLen):
      # open serial port
      self.ser = serial.Serial(strPort, 9600)

      self.ax = deque([0.0]*maxLen)
      self.ay = deque([0.0]*maxLen)
      self.maxLen = maxLen

  # add to buffer
  def addToBuf(self, buf, val):
      if len(buf) < self.maxLen:
          buf.append(val)
      else:
          buf.pop()
          buf.appendleft(val)

  # add data
  def add(self, data):
      assert(len(data) == 2)
      self.addToBuf(self.ax, data[0])
      self.addToBuf(self.ay, data[1])

  # update plot
  def update(self, frameNum, a0, a1):
      try:
          line = self.ser.readline()
          data = [float(val) for val in line.split()]
          # print data
          if(len(data) == 2):
              self.add(data)
              a0.set_data(range(self.maxLen), self.ax)
              a1.set_data(range(self.maxLen), self.ay)
      except KeyboardInterrupt:
          print('exiting')
      
      return a0, 

  # clean up
  def close(self):
      # close serial
      self.ser.flush()
      self.ser.close()    

# main() function
def main():
  # create parser
  parser = argparse.ArgumentParser(description="LDR serial")
  # add expected arguments
  parser.add_argument('--port', dest='port', required=True)

  # parse args
  args = parser.parse_args()
  
  #strPort = '/dev/tty.usbserial-A7006Yqh'
  strPort = args.port

  print('reading from serial port %s...' % strPort)

  # plot parameters
  analogPlot = AnalogPlot(strPort, 100)

  print('plotting data...')

  # set up animation
  fig = plt.figure()
  ax = plt.axes(xlim=(0, 100), ylim=(0, 1023))
  a0, = ax.plot([], [])
  a1, = ax.plot([], [])
  anim = animation.FuncAnimation(fig, analogPlot.update, 
                                 fargs=(a0, a1), 
                                 interval=50)

  # show plot
  plt.show()
  
  # clean up
  analogPlot.close()

  print('exiting.')
  

# call main
if __name__ == '__main__':
  main()

nice python

Really nice approach. Might try to use this in a ShrimpKey lesson plan, thanks.

Unfornately it is very slow. When the sensor data changes, I'll wait 10 seconds. Then it changes.

yeah its really slow :(

That is really awesome. Is there a way to add labels on the right side of the Y-Axis (for example, for plotting both altitude and pressure, each with different units)? I'm still learning about these tools and am curious if there's a quick solution for this. How about adding a little text box right on the graph? Thanks!

Where in the code do you input the Port your running your Arduino on. I don't know where to insert my 'COM4' port location?????

I tried to run your code to my arduino test, but it seems that not worked. It is simply don't plotting anything. thanks for the help

@exclaimedpower while running your script you can use --port flag in linux
eg your command will be
python ldr.py --port COM4

I'm having this problem.

$ python3 ldr.py --port /dev/tty.usbmodem411
Traceback (most recent call last):
File "ldr.py", line 10, in
import sys, serial, argparse
ImportError: No module named 'serial'

I've installed $python install serial

@fmendes75 I think that I installed 'pyserial' with pip install pyserial (or pip3 install pyserial). Try, I guess that this solve your problem

Nice. Thanks for sharing !

Very helpfull but I have this error when I run my code usage: ldr.py [-h] --port PORT ldr.py: error: the following arguments are required: --port
can you help me ?

I'm having the following error:
usage: ldr.py [-h] --port PORT
ldr.py: error: the following arguments are required: --port
An exception has occurred, use %tb to see the full traceback.

Hi, i really like your job. Can you tell me how could i change de direction of the grafic?, for this code run to turn left, i want to right

JuanDanielSoto,

Change addToBuffer to:

add to buffer

def addToBuf(self, buf, val):
if len(buf) < self.maxLen:
buf.append(val)
#buf.extendleft(val)
else:
#buf.pop()
#buf.appendleft(val)
buf.popleft()
buf.append(val)

can we use pyfirmata for the same code ?and how we edit that in this code