laser dust sensor - pm 2.5 plotter

sensor_data.py

import serial
import time
import struct
import datetime
import matplotlib.pyplot as plt

# for use with sds021 sensor or similar 
# https://www.aliexpress.com/item/NOVA-PM2-5-Air-particle-dust-sensor-SDS021-laser-inside-digital-output-SDS021-Laser-PM2-5/32638192686.html

# replace with your serial port
ser = serial.Serial('/dev/tty.wchusbserial1410',9600)

pm_25 = 0 
pm_10 = 0 
pm_25_old = 0 
pm_10_old = 0 
x = []
y = []
raw = []
count = 0


def checksum(data):
	checksum = 0
	for x in range(2,8):
	#	print(x,data[x],ord(data[x]))
		checksum =checksum+ord(data[x])
	#print(checksum%256,ord(data[8]))
	if(ord(data[8] ) == (checksum%256)):
		return True

	else:
		return False
def calculate(high,low):
	return ((ord(high)*256)+ord(low))/10.0

# do some smoothing 
def smooth(old,new,alpha=0.25):
	if old is None:
		old = new
	return (old + alpha * (new - old))

# to do - calculate AQI

plt.ion()


while True:
	message = ser.read(10)
	print("read data",message)
	if checksum(message):
		pm_10_old = pm_10
		pm_25_old = pm_25
		pm_25 = smooth(pm_25_old,calculate(message[3],message[2]))
		pm_10 = smooth(pm_10_old,calculate(message[5],message[4]))
		raw.append(calculate(message[3],message[2]))
		x.append(count)
		y.append(pm_25)
		print("pm2.5",pm_25)
		print("pm10",pm_10)
		plt.plot(x,y,'g')
		#plt.plot(x,raw,'r')
		plt.pause(0.0001) #Note this correction
		count = count + 1