Tag Archives: Python

Arduino and Ethernet Shield — Ethernet Shields are available which allow the arduino to act as a server

In the previous lessons we have seen that powerful analytic and graphic programs can be written that allow data taken from the arduino to be displayed on a PC via Python. We have shown how the arduino can be connected to a PC by either a serial cable or Xbee radios. To fully unleash the power of the arduino, it can be set up as a server, and connected to a network via Ethernet. In this lesson, we will show how to set the arduino up as a server which is controlled and queried by clients on PC’s on the same network. In order to complete this tutorial, you will need an Arduino Uno and an Ethernet shield. The Ethernet Shield is a relatively expensive component, but I suggest getting an authentic arduino made shield, as I have had poor results from the cheap knock offs. Understand that this lesson is intended for High School students to show them a simple technique for connecting the arduino to a network. It is not an exhaustive treatise on Ethernet communication. The goal is to provide a simple protocol which should allow you to get your arduino talking over Ethernet. It requires that you already know, or can figure out how to assign a mac address and IP address in your router. Some arduino Ethernet shields have a sticker with a mac address. If your Ethernet shield has a sticker with mac address, use that one. If it does not, you will need to come up with a unique mac address. If you are at school, the network administrator can help you get the router configured. I can not provide support in getting this to work on your network, as there are many variables. The techniques provided in this tutorial should work for most networks. This tutorial does not present the most efficient or elegant solution, but the goal is a simple protocol for people just getting started. The video below gives a step-by-step demonstration of setting up the arduino as a server, and Python on a PC as the client. It uses UDP protocol to transfer data packets.

In order to get the arduino to work over Ethernet, you must first assign an IP address to the arduino in your router. If you just plug the arduino with shield into the network, your router might assign an IP and report a mac address. If this is the case, you need to have the router assign those addresses permanently to the arduino. The bottom line is that the IP address and mac address you identify in the arduino code must match the IP address and mac address assigned in the router. I can not provide any additional help on that issue as there are so many different possible networks. You have to figure out how to do that.

Once you have the IP address and mac address sorted out, you will need to set up the arduino as a server. The video above explains how to do this, and results in this code. Note that your IP address and mac address must be set to a suitable configuration for your router and network. The numbers I use in this code would not work for your network.

This is the code developed in the video to set the arduino up:

#include <Ethernet.h> //Load Ethernet Library
#include <EthernetUdp.h> //Load UDP Library
#include <SPI.h> //Load the SPI Library

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xEE}; //Assign a mac address
IPAddress ip(10, 1, 15, 243); //Assign my IP adress
unsigned int localPort = 5000; //Assign a Port to talk over
char packetBuffer[UDP_TX_PACKET_MAX_SIZE];
String datReq; //String for our data
int packetSize; //Size of Packet
EthernetUDP Udp; //Define UDP Object

void setup() {
  
Serial.begin(9600); //Turn on Serial Port
Ethernet.begin(mac, ip); //Initialize Ethernet
Udp.begin(localPort); //Initialize Udp
delay(1500); //delay
}

void loop() {
  
  packetSize = Udp.parsePacket(); //Read theh packetSize
  
  if(packetSize>0){ //Check to see if a request is present
  
  Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE); //Reading the data request on the Udp
  String datReq(packetBuffer); //Convert packetBuffer array to string datReq
  
  if (datReq =="Red") { //See if Red was requested
  
    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());  //Initialize Packet send
    Udp.print("You are Asking for Red"); //Send string back to client 
    Udp.endPacket(); //Packet has been sent
  }
   if (datReq =="Green") { //See if Green was requested
  
    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());  //Initialize Packet send
    Udp.print("You are Asking for Green"); //Send string back to client 
    Udp.endPacket(); //Packet has been sent
   }
    if (datReq =="Blue") { //See if Red was requested
  
    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());  //Initialize Packet send
    Udp.print("You are Asking for Blue"); //Send string back to client 
    Udp.endPacket(); //Packet has been sent
    }
  }
  memset(packetBuffer, 0, UDP_TX_PACKET_MAX_SIZE);
}

#include <Ethernet.h> //Load Ethernet Library

#include <EthernetUdp.h> //Load UDP Library

#include <SPI.h> //Load the SPI Library

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xEE}; //Assign a mac address

IPAddress ip(10, 1, 15, 243); //Assign my IP adress

unsigned int localPort = 5000; //Assign a Port to talk over

char packetBuffer[UDP_TX_PACKET_MAX_SIZE];

String datReq; //String for our data

int packetSize; //Size of Packet

EthernetUDP Udp; //Define UDP Object

void setup() {

Serial.begin(9600); //Turn on Serial Port

Ethernet.begin(mac, ip); //Initialize Ethernet

Udp.begin(localPort); //Initialize Udp

delay(1500); //delay

}

void loop() {

packetSize = Udp.parsePacket(); //Read theh packetSize

if(packetSize>0){ //Check to see if a request is present

Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE); //Reading the data request on the Udp

String datReq(packetBuffer); //Convert packetBuffer array to string datReq

if (datReq =="Red") { //See if Red was requested

Udp.beginPacket(Udp.remoteIP(), Udp.remotePort()); //Initialize Packet send

Udp.print("You are Asking for Red"); //Send string back to client

Udp.endPacket(); //Packet has been sent

}

if (datReq =="Green") { //See if Green was requested

Udp.beginPacket(Udp.remoteIP(), Udp.remotePort()); //Initialize Packet send

Udp.print("You are Asking for Green"); //Send string back to client

Udp.endPacket(); //Packet has been sent

}

if (datReq =="Blue") { //See if Red was requested

Udp.beginPacket(Udp.remoteIP(), Udp.remotePort()); //Initialize Packet send

Udp.print("You are Asking for Blue"); //Send string back to client

Udp.endPacket(); //Packet has been sent

}

memset(packetBuffer, 0, UDP_TX_PACKET_MAX_SIZE);

}

Once you have this code in your arduino, ping the IP address of the arduino from your PC cmd line. Make sure your PC can talk to the arduino by successfully pinging it. If you get an error while you are trying to ping the arduino, you will have to stop and get figured out what is wrong. There is no reason to proceed with the lesson until you can successfully ping the arduino.

Once you can ping the arduino, you are ready to set up a client in Python. The code below is what we developed in the video. You will need to watch the video in order to understand the code. Also note, that the IP address in the code below is the IP address of the Arduino, NOT the PC. You should set this to whatever IP address is of YOUR arduino.

from socket import *
import time

address = ( '10.1.15.243', 5000) #Defind who you are talking to (must match arduino IP and port)
client_socket = socket(AF_INET, SOCK_DGRAM) #Set Up the Socket
client_socket.settimeout(1) #only wait 1 second for a resonse

while(1): #Main Loop

    data = "Blue" #Set data to Blue Command
    client_socket.sendto(data, address) #send command to arduino
    try:
        rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino
        print rec_data #Print the response from Arduino
    except:
        pass

    time.sleep(2) #delay before sending next command

    data = "Red" #Set data to Blue Command
    client_socket.sendto(data, address) #send command to arduino
    try:
        rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino
        print rec_data #Print the response from Arduino
    except:
        pass

    time.sleep(2) #delay before sending next command
    
    data = "Green" #Set data to Blue Command
    client_socket.sendto(data, address) #send command to arduino
    try:
        rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino
        print rec_data #Print the response from Arduino
    except:
        pass
    time.sleep(2) #delay before sending next command

from socket import *

import time

address = ( '10.1.15.243', 5000) #Defind who you are talking to (must match arduino IP and port)

client_socket = socket(AF_INET, SOCK_DGRAM) #Set Up the Socket

client_socket.settimeout(1) #only wait 1 second for a resonse

while(1): #Main Loop

data = "Blue" #Set data to Blue Command

client_socket.sendto(data, address) #send command to arduino

try:

rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino

print rec_data #Print the response from Arduino

except:

pass

time.sleep(2) #delay before sending next command

data = "Red" #Set data to Blue Command

client_socket.sendto(data, address) #send command to arduino

try:

rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino

print rec_data #Print the response from Arduino

except:

pass

time.sleep(2) #delay before sending next command

data = "Green" #Set data to Blue Command

client_socket.sendto(data, address) #send command to arduino

try:

rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino

print rec_data #Print the response from Arduino

except:

pass

time.sleep(2) #delay before sending next command

Again, this is a bit of a tricky thing to set up, but if you get the PC successfully pinging the arduino, everything else should be straightforward.

Arduino with Python, Tutorial

Python with Arduino LESSON 15: Configuring and Using the Xbee Radios

March 18, 2015 admin

This lesson describes how to program the Xbee Series 1 radios. It will work with either the standard Series 1 (S1) or the Series 1 Pro models. The Pro radios are higher power and will give greater range, but they cost more. The radios are configured using X-CTU software, which can be downloaded here. The video gives step by step instructions on how to configure and use the radios to communicate wirelessly over the serial port. Lesson 14 gives information on the hardware needed. Lessons 1-13 sill show you how to communicate between Python and Arduino if you need to get caught up on basic serial communication and interfacing arduino and python. The techniques provided in the video above, however, should work for just about any arduino project where you want to communicate between two arduinos, an arduino and PC, or between two PCs.

Arduino with Python, Tutorial

Python with Arduino LESSON 13: Calculating Height from Pressure measurements from BMP180 Pressure Sensor.

July 25, 2014 admin

It is time to bring together a lot of things we have learned in our earlier lessons to create a Height-O-Meter, which will plot how high our BMP180 pressure sensor is above the floor. For this lesson we make simplifying assumption of constant temperature. When we use the sensor for our space probe or other high altitude experiments we will need to derive the equation again to take into account changing temperature. We went through the math of calculating height from changing pressure in LESSON 12.

In this lesson, we start with the software we developed in LESSON 11 for measuring, streaming, and plotting pressure and temperature data from the BMP180 sensor.

Remember, we connect the sensor to the Arduino as follows:

Connecting Up the BMP180 Pressure and Temperature Sensor
BMP180 Pin	Arduino Pin
Vin	5V
GND	GND
SCL	A5
SDA	A4

The software we are using on the arduino side is shown below, from LESSON 11.

#include "Wire.h"    // imports the wire library for talking over I2C 
#include "Adafruit_BMP085.h"  // import the Pressure Sensor Library
Adafruit_BMP085 mySensor;  // create sensor object called mySensor

float tempC;  // Variable for holding temp in C
float tempF;  // Variable for holding temp in F
float pressure; //Variable for holding pressure reading

void setup(){
Serial.begin(115200); //turn on serial monitor
mySensor.begin();   //initialize mySensor
}

void loop() {
tempC = mySensor.readTemperature(); //  Be sure to declare your variables
tempF = tempC*1.8 + 32.; // Convert degrees C to F
pressure=mySensor.readPressure(); //Read Pressure


Serial.print(tempF);
Serial.print(" , ");
Serial.println(pressure);
delay(250); //Pause between readings.
}

#include "Wire.h" // imports the wire library for talking over I2C

#include "Adafruit_BMP085.h" // import the Pressure Sensor Library

Adafruit_BMP085 mySensor; // create sensor object called mySensor

float tempC; // Variable for holding temp in C

float tempF; // Variable for holding temp in F

float pressure; //Variable for holding pressure reading

void setup(){

Serial.begin(115200); //turn on serial monitor

mySensor.begin(); //initialize mySensor

}

void loop() {

tempC = mySensor.readTemperature(); // Be sure to declare your variables

tempF = tempC*1.8 + 32.; // Convert degrees C to F

pressure=mySensor.readPressure(); //Read Pressure

Serial.print(tempF);

Serial.print(" , ");

Serial.println(pressure);

delay(250); //Pause between readings.

}

We modify the Python code from LESSON 11 as explained in the video above to get this code for the Python side.

import serial # import Serial Library
import numpy as np  # Import numpy
import matplotlib.pyplot as plt #import matplotlib library
from drawnow import *
import time

tempF= []   #Array for our Temperature dat
pressure=[] #Array for our Pressure Data
ht=[]       #Array for our calculated Heights
arduinoData = serial.Serial('com11', 115200) #Creating our serial object named arduinoData
plt.ion() #Tell matplotlib you want interactive mode to plot live data
cnt=0

def makeFig(): #Create a function that makes our desired plot
    plt.ylim(0,10)                                 #Set y min and max values
    plt.title('My SuperCool Height-O-Meter')      #Plot the title
    plt.grid(True)                                  #Turn the grid on
    plt.ylabel('Height in Feet')                            #Set ylabels
    plt.plot(ht, 'ro-', label='Height')       #plot the height array
    plt.legend(loc='upper left')                    #plot the legend
    plt2=plt.twinx()                                #Create a second y axis
    plt.ylim(75,85)                           #Set limits of second y axis- adjust to readings you are getting
    plt2.plot(tempF, 'b^-', label='tempF') #plot temperature array
    plt2.set_ylabel('temp F')                    #label second y axis
    plt2.ticklabel_format(useOffset=False)           #Force matplotlib to NOT autoscale y axis
    plt2.legend(loc='upper right')                  #plot the legend

tempBucket = 0  #Create bucket to hold sum of temperature readings
PBucket=0       #Create bucket to hold sum of pressure readings

print "PLease put Sensor Circuit on Ground for Calibration"  #Calibrate sensor for readings on floor, P0
print "5"           #Give user time to put sensor on floor
time.sleep(1)
print "4"
time.sleep(1)
print "3"
time.sleep(1)
print "2"
time.sleep(1)
print "1"
time.sleep(1)
print "Calibrating Sensor . . ."

for i in np.arange(1,11,1):  #Loop ten times to take ten measurements
    while (arduinoData.inWaiting()==0): #Wait here until there is data
        pass #do nothing
    arduinoString = arduinoData.readline() #read the line of text from the serial port
    dataArray = arduinoString.split(',')   #Split it into an array called dataArray
    temp = float( dataArray[0])            #Convert first element to floating number and put in temp
    P =    float( dataArray[1])            #Convert second element to floating number and put in P
    print "P = ",P, " , Temp= ", temp
    tempBucket=tempBucket + temp
    PBucket = PBucket + P
P0 = PBucket/10  #Calcualte average pressure on floor
tempK = ((tempBucket/10)-32)/1.8 +273.15  #Calculate average temperature on floor in K

print "Baseline Temp in K is: ", tempK #Print resulrs
print "Baseline Pressure inPa. : ", P0
    


while True: # While loop that loops forever
    while (arduinoData.inWaiting()==0): #Wait here until there is data
        pass #do nothing
    arduinoString = arduinoData.readline() #read the line of text from the serial port
    dataArray = arduinoString.split(',')   #Split it into an array called dataArray
    temp = float( dataArray[0])            #Convert first element to floating number and put in temp
    P =    float( dataArray[1])            #Convert second element to floating number and put in P
    h=98.57*tempK*np.log(P0/P)
    ht.append(h)
    tempF.append(temp)                     #Build our tempF array by appending temp readings
    pressure.append(P)                     #Building our pressure array by appending P readings
    drawnow(makeFig)                       #Call drawnow to update our live graph
    plt.pause(.000001)                     #Pause Briefly. Important to keep drawnow from crashing
    cnt=cnt+1
    if(cnt>50):                            #If you have 50 or more points, delete the first one from the array
        tempF.pop(0)                       #This allows us to just see the last 50 data points
        pressure.pop(0)
        ht.pop(0)

import serial # import Serial Library

import numpy as np # Import numpy

import matplotlib.pyplot as plt #import matplotlib library

from drawnow import *

import time

tempF= [] #Array for our Temperature dat

pressure=[] #Array for our Pressure Data

ht=[] #Array for our calculated Heights

arduinoData = serial.Serial('com11', 115200) #Creating our serial object named arduinoData

plt.ion() #Tell matplotlib you want interactive mode to plot live data

cnt=0

def makeFig(): #Create a function that makes our desired plot

plt.ylim(0,10) #Set y min and max values

plt.title('My SuperCool Height-O-Meter') #Plot the title

plt.grid(True) #Turn the grid on

plt.ylabel('Height in Feet') #Set ylabels

plt.plot(ht, 'ro-', label='Height') #plot the height array

plt.legend(loc='upper left') #plot the legend

plt2=plt.twinx() #Create a second y axis

plt.ylim(75,85) #Set limits of second y axis- adjust to readings you are getting

plt2.plot(tempF, 'b^-', label='tempF') #plot temperature array

plt2.set_ylabel('temp F') #label second y axis

plt2.ticklabel_format(useOffset=False) #Force matplotlib to NOT autoscale y axis

plt2.legend(loc='upper right') #plot the legend

tempBucket = 0 #Create bucket to hold sum of temperature readings

PBucket=0 #Create bucket to hold sum of pressure readings

print "PLease put Sensor Circuit on Ground for Calibration" #Calibrate sensor for readings on floor, P0

print "5" #Give user time to put sensor on floor

time.sleep(1)

print "4"

time.sleep(1)

print "3"

time.sleep(1)

print "2"

time.sleep(1)

print "1"

time.sleep(1)

print "Calibrating Sensor . . ."

for i in np.arange(1,11,1): #Loop ten times to take ten measurements

while (arduinoData.inWaiting()==0): #Wait here until there is data

pass #do nothing

arduinoString = arduinoData.readline() #read the line of text from the serial port

dataArray = arduinoString.split(',') #Split it into an array called dataArray

temp = float( dataArray[0]) #Convert first element to floating number and put in temp

P = float( dataArray[1]) #Convert second element to floating number and put in P

print "P = ",P, " , Temp= ", temp

tempBucket=tempBucket + temp

PBucket = PBucket + P

P0 = PBucket/10 #Calcualte average pressure on floor

tempK = ((tempBucket/10)-32)/1.8 +273.15 #Calculate average temperature on floor in K

print "Baseline Temp in K is: ", tempK #Print resulrs

print "Baseline Pressure inPa. : ", P0

while True: # While loop that loops forever

while (arduinoData.inWaiting()==0): #Wait here until there is data

pass #do nothing

arduinoString = arduinoData.readline() #read the line of text from the serial port

dataArray = arduinoString.split(',') #Split it into an array called dataArray

temp = float( dataArray[0]) #Convert first element to floating number and put in temp

P = float( dataArray[1]) #Convert second element to floating number and put in P

h=98.57*tempK*np.log(P0/P)

ht.append(h)

tempF.append(temp) #Build our tempF array by appending temp readings

pressure.append(P) #Building our pressure array by appending P readings

drawnow(makeFig) #Call drawnow to update our live graph

plt.pause(.000001) #Pause Briefly. Important to keep drawnow from crashing

cnt=cnt+1

if(cnt>50): #If you have 50 or more points, delete the first one from the array

tempF.pop(0) #This allows us to just see the last 50 data points

pressure.pop(0)

ht.pop(0)

Please go through video for complete description of this software. Remember this is only valid for small changes in height over which temperature is constant.

Arduino with Python

Python with Arduino LESSON 12: Approximating Changes in Height from Changes in Pressure

July 25, 2014 admin

In LESSON 9 we learned how to hook up a BMP180 Pressure Sensor and make pressure and temperature readings. Then in LESSON 11 we learned how to stream that data to Matplotlib and create live graphs and charts of our data that update in real time. We could see that as we moved the pressure sensor up and down, we could see the pressure change, as the pressure decreases with increasing elevation.

This leads to the interesting question of whether we can use our circuit developed in LESSON 9 to create a Height-O-Meter . . . a simple device that will measure the height above the floor.

The math to calculate altitude vs. pressure turns out to be very complex. Particularly, if we wanted something for our high altitude balloon flights, or for model rocketry. It turns out that for the case of measuring height inside and for relatively small changes in height we can make simplifying assumptions that make things much easier. The assumption we will make is that temperature does not change much over the range of our experiment. With this assumption, we can create our own Height-O-Meter. To do this though, we do need to to through some math. I show my math below, and go through it step-by-step in the video. Remember, this simplified approach is only valid for playing around with small changes in height. We will have to do the more complicated math when we make our high altitude balloon probe. For now though, this math will work pretty well.

Height and Pressure — Calculate Changes in Height from Changes in Pressure

We can rearrange the equation to solve for height as a function of pressure.

Height Pressure — Calculating Height from Pressure Changes

Arduino with Python, Tutorial

Python with Arduino LESSON 11: Plotting and Graphing Live Data from Arduino with Matplotlib

July 24, 2014 admin

We now have all the pieces put together to allow us to plot live data from the Arduino. If you have kept up with the earlier lessons, you will now have everything you need. If you have not done the earlier lessons, make sure you have python 2.7, vPython and pySerial installed from Python with Arduino LESSON 2. Make sure you have installed matplotlib (Python with Arduino LESSON 7), and install drawnow (Python with Arduino LESSON 10). Also, you need to build the BMP180 circuit and get the arduino programmed up as explained in Python with Arduino LESSON 9. With this business taken care of, you are now ready to start plotting live data.

Pressure Data — This chart shows live pressure and temperature data being plotted in real time

We are using the Adafruit BMP180 pressure sensor. We showed how to hook it up and program it in LESSON 9. As a reminder, we are using this code for the arduino. LESSON 9 explained in detail how the code works.

#include "Wire.h"    // imports the wire library for talking over I2C 
#include "Adafruit_BMP085.h"  // import the Pressure Sensor Library
Adafruit_BMP085 mySensor;  // create sensor object called mySensor

float tempC;  // Variable for holding temp in C
float tempF;  // Variable for holding temp in F
float pressure; //Variable for holding pressure reading

void setup(){
Serial.begin(115200); //turn on serial monitor
mySensor.begin();   //initialize mySensor
}

void loop() {
tempC = mySensor.readTemperature(); //  Be sure to declare your variables
tempF = tempC*1.8 + 32.; // Convert degrees C to F
pressure=mySensor.readPressure(); //Read Pressure


Serial.print(tempF);
Serial.print(" , ");
Serial.println(pressure);
delay(250); //Pause between readings.
}

#include "Wire.h" // imports the wire library for talking over I2C

#include "Adafruit_BMP085.h" // import the Pressure Sensor Library

Adafruit_BMP085 mySensor; // create sensor object called mySensor

float tempC; // Variable for holding temp in C

float tempF; // Variable for holding temp in F

float pressure; //Variable for holding pressure reading

void setup(){

Serial.begin(115200); //turn on serial monitor

mySensor.begin(); //initialize mySensor

}

void loop() {

tempC = mySensor.readTemperature(); // Be sure to declare your variables

tempF = tempC*1.8 + 32.; // Convert degrees C to F

pressure=mySensor.readPressure(); //Read Pressure

Serial.print(tempF);

Serial.print(" , ");

Serial.println(pressure);

delay(250); //Pause between readings.

}

The video in this lesson above explains step-by-step how to develop the code on the Python side, and how matplotlib and drawnow work together to make live graphs and plots of data streaming from the arduino in real time. The code below is what we developed in the video. Do not simply cut and paste this code, but make sure that you understand it so you are able to create your own live graphing programs from scratch. If you are in my class, you will be required to be able to develop live graphing code like this from scratch, so don’t take a shortcut and copy and paste.

import serial # import Serial Library
import numpy  # Import numpy
import matplotlib.pyplot as plt #import matplotlib library
from drawnow import *

tempF= []
pressure=[]
arduinoData = serial.Serial('com11', 115200) #Creating our serial object named arduinoData
plt.ion() #Tell matplotlib you want interactive mode to plot live data
cnt=0

def makeFig(): #Create a function that makes our desired plot
    plt.ylim(80,90)                                 #Set y min and max values
    plt.title('My Live Streaming Sensor Data')      #Plot the title
    plt.grid(True)                                  #Turn the grid on
    plt.ylabel('Temp F')                            #Set ylabels
    plt.plot(tempF, 'ro-', label='Degrees F')       #plot the temperature
    plt.legend(loc='upper left')                    #plot the legend
    plt2=plt.twinx()                                #Create a second y axis
    plt.ylim(93450,93525)                           #Set limits of second y axis- adjust to readings you are getting
    plt2.plot(pressure, 'b^-', label='Pressure (Pa)') #plot pressure data
    plt2.set_ylabel('Pressrue (Pa)')                    #label second y axis
    plt2.ticklabel_format(useOffset=False)           #Force matplotlib to NOT autoscale y axis
    plt2.legend(loc='upper right')                  #plot the legend
    

while True: # While loop that loops forever
    while (arduinoData.inWaiting()==0): #Wait here until there is data
        pass #do nothing
    arduinoString = arduinoData.readline() #read the line of text from the serial port
    dataArray = arduinoString.split(',')   #Split it into an array called dataArray
    temp = float( dataArray[0])            #Convert first element to floating number and put in temp
    P =    float( dataArray[1])            #Convert second element to floating number and put in P
    tempF.append(temp)                     #Build our tempF array by appending temp readings
    pressure.append(P)                     #Building our pressure array by appending P readings
    drawnow(makeFig)                       #Call drawnow to update our live graph
    plt.pause(.000001)                     #Pause Briefly. Important to keep drawnow from crashing
    cnt=cnt+1
    if(cnt>50):                            #If you have 50 or more points, delete the first one from the array
        tempF.pop(0)                       #This allows us to just see the last 50 data points
        pressure.pop(0)

import serial # import Serial Library

import numpy # Import numpy

import matplotlib.pyplot as plt #import matplotlib library

from drawnow import *

tempF= []

pressure=[]

arduinoData = serial.Serial('com11', 115200) #Creating our serial object named arduinoData

plt.ion() #Tell matplotlib you want interactive mode to plot live data

cnt=0

def makeFig(): #Create a function that makes our desired plot

plt.ylim(80,90) #Set y min and max values

plt.title('My Live Streaming Sensor Data') #Plot the title

plt.grid(True) #Turn the grid on

plt.ylabel('Temp F') #Set ylabels

plt.plot(tempF, 'ro-', label='Degrees F') #plot the temperature

plt.legend(loc='upper left') #plot the legend

plt2=plt.twinx() #Create a second y axis

plt.ylim(93450,93525) #Set limits of second y axis- adjust to readings you are getting

plt2.plot(pressure, 'b^-', label='Pressure (Pa)') #plot pressure data

plt2.set_ylabel('Pressrue (Pa)') #label second y axis

plt2.ticklabel_format(useOffset=False) #Force matplotlib to NOT autoscale y axis

plt2.legend(loc='upper right') #plot the legend

while True: # While loop that loops forever

while (arduinoData.inWaiting()==0): #Wait here until there is data

pass #do nothing

arduinoString = arduinoData.readline() #read the line of text from the serial port

dataArray = arduinoString.split(',') #Split it into an array called dataArray

temp = float( dataArray[0]) #Convert first element to floating number and put in temp

P = float( dataArray[1]) #Convert second element to floating number and put in P

tempF.append(temp) #Build our tempF array by appending temp readings

pressure.append(P) #Building our pressure array by appending P readings

drawnow(makeFig) #Call drawnow to update our live graph

plt.pause(.000001) #Pause Briefly. Important to keep drawnow from crashing

cnt=cnt+1

if(cnt>50): #If you have 50 or more points, delete the first one from the array

tempF.pop(0) #This allows us to just see the last 50 data points

pressure.pop(0)

You should be seeing data like the graph on the top of this lesson. You will probably need to adjust your y-axis scale parameters in Python to ensure the scale is suitable for the data you are taking. If your chart is blank, likely your y-scales are not right for your data measurements.

Technology Tutorials

Tag Archives: Python

Python with Arduino LESSON 16: Simple Client Server Configuration over Ethernet

Python with Arduino LESSON 15: Configuring and Using the Xbee Radios

Python with Arduino LESSON 13: Calculating Height from Pressure measurements from BMP180 Pressure Sensor.

Connecting Up the BMP180 Pressure and Temperature Sensor

Python with Arduino LESSON 12: Approximating Changes in Height from Changes in Pressure

Python with Arduino LESSON 11: Plotting and Graphing Live Data from Arduino with Matplotlib

Making The World a Better Place One High Tech Project at a Time. Enjoy!