Tag Archives: Python

In this lesson we will actually begin to control the GPIO pins from the Raspberry Pi. We will start by looking at how to write a pin high or low. We will be doing this in the Python programming language. A really important thing to remember is that the default “Pi” user does not have access to the pins, so for these examples to work, you must run the programs with “sudo”. The sudo command executes as super user, and will give the program access to the GPIO pins.

To begin with, lets build a simple circuit. If you purchased the kit we showed in lesson 1, you should have all the components you need to follow along with these examples. If you have not purchased a kit yet, you can get one on amazon.com HERE. In this first lesson we will just be looking at blinking an LED. So, you can now go ahead and hook up the following circuit. For reference, we show below the pinout of the Raspberry Pi.

Raspberry Pi 2 Pinout — This figure shows the Raspberry Pi GPIO pinout

In this example we will be using physical pin 9 as a ground, and physical pin 11 as the control pin. You can now go ahead and hook up the following circuit. Please remember the direction you plug the LED in matters . . . the long leg needs to connect to pin 11. The resistor used should be about 330 ohms.

Raspberry Pi Circuit — This Circuit Will Blink a Red LED

In order to become familiar with the commands, I like to start in the Python shell. Basically, we give the commands to python one line at a time and watch what happens. Then later, we can write and run programs.

Note that recent versions of the Raspberry Pi distribution include the RPi library, but if you have an older distribution, update your system using these commands:

$ sudo apt-get update

and

$ sudo apt-get upgrade

If you have not done this is a while, it can take some time to download and install the updates.

We are now ready to begin to work with the GPIO pins. To enter the python shell, open a terminal window on the Raspberry Pi, and you will want to type:

$ sudo python

Be sure and use the sudo command above, as that will give you administrative access to the GPIO pins. Now, you should get the python command shell prompt, that looks like this:

>>>

At this point, any command you type will be executed by the python interpreter. You can basically execute a python program one line at a time. Note, to exit the python shell type Ctrl-d.

OK, so lets see if we can control the LED!

First, we need to import the RPi library. Note this is case sensitive, so be careful to do capitalization exactly:

>>> import RPi.GPIO as GPIO

Now, we need to initialize the GPIO to use either the BOARD or the BCM pin numbering schemes. In the diagram at the top of this lesson, the BOARD numbering convention is shown in the center two columns. If you want to use the BCM numbering scheme, you would use the numbers indicated in the outer two columns. In these examples, I want to use the physical pin numbers, as that is easier to me to keep track of things. Hence, I will want to use the BOARD scheme. I can do that with this command:

>>>GPIO.setmode(GPIO.BOARD)

As you can imagine, if you want to use BCM, BOARD should be replaced with BCM in the command above.

If you remember in our Arduino lessons, we had to do pinmode commands to tell the arduino whether pins are inputs or outputs. We do an analogous thing in Raspberry Pi. We need to tell the Pi whether we will be using a pin as an input or output. In the wiring diagram above, you can see that we want to power the LED from physical pin 11, so we need to set that as an output.

>>>GPIO.setup(11,GPIO.OUT)

We are now ready to turn the LED on. We can do this by setting pin 11 to True:

>>>GPIO.output(11,True)

Now to turn the LED off, we can do:

>>>GPIO.output(11,False)

You can now play around with different GPIO pins, and turn the LED on and off as you like. Before leaving the Python shell, be sure to clean up the GPIO. You do this by giving the cleanup command:

>>>GPIO.cleanup()

This will ensure you do not get error messages if you try to work with the GPIO pins again. It is a good practice to always cleanup after you are done.

Raspberry Pi

Raspberry Pi Linux LESSON 24: Running Python on the Raspberry Pi

May 29, 2015 admin

If you have been following these lessons by this time you should be fairly comfortable with the Linux operating system, and you should know enough commands to do what you need to from the terminal window and command line. We now want to move forward to actually start doing things with the Pi. In order to do this, we will be using the Python programming language.

Arduino with Python, Tutorial

Python with Arduino LESSON 17: Sending and Receiving Data Over Ethernet

April 6, 2015 admin

Arduino Ethernet — This circuit contains an Arduino Nano and Pressure Sensor Communicating over Ethernet

In LESSON 16 we showed a simple Client Server model that allows us to send strings between Python running on a PC and the arduino over Ethernet. That lesson simply passed strings back and forth to show a very basic Server on Arduino, and Python acting as the Client. In this lesson we show a more practical example, with the Arduino connected to an Adafruit BMP180 Pressure Sensor. In order to complete this lesson, you will need an Arduino, an Ethernet Shield, and the Pressure Sensor. If you do not have this particular pressure sensor, you can probably follow along in the lesson using whatever sensor you have that is of interest. The video will take you through the tutorial step-by-step, and then the code we developed is shown below.

The key issue in getting this project to work is to get your mac address and IP address from your router or network. If you are at school, simply speak to your network administrator, and he will help you get an IP address for your arduino. If you are at home, you will need to connect to your router from a browser, and configure it to assign an IP address and agree on a mac address for your arduino. 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. There are thousands of possible routers and networks out there, so I can not help you with that part. But if you look in the router documentation, you should be able to get the IP address and mac address worked out. The arduino itself does not have a hard wired mac address, but you set the mac address in the arduino software, and the IP address as well. The key thing is that the mac address is unique on your network, and the router and arduino agree on the IP address and mac address. If you have a clearer way to explain this, please leave a comment below.

This is the server side software to run on the arduino. Again, you should use a suitable IP address and mac address for your network. Do not think you can just copy the ones I use in the code below.

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

#include "Wire.h" //imports the wire library
#include "Adafruit_BMP085.h" // import the Pressure/Temperature sensor library
Adafruit_BMP085 mySensor; //Create a sensor object

float tempC; //Declare variable for Temp in C
float tempF; //Declare variable for Temp in F
float Pressure; //Declare a variable for Pressure

byte mac[] ={ 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xEE}; //Assign mac address
IPAddress ip(10, 1, 15, 243); //Assign the IP Adress
unsigned int localPort = 5000; // Assign a port to talk over
char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //dimensian a char array to hold our data packet
String datReq; //String for our data
int packetSize; //Size of the packet
EthernetUDP Udp; // Create a UDP Object

void setup() {
  
  Serial.begin(9600); //Initialize Serial Port 
  Ethernet.begin( mac, ip); //Inialize the Ethernet
  Udp.begin(localPort); //Initialize Udp
  delay(1500); //delay
  mySensor.begin(); //initialize pressure-temp sensor
  

}

void loop() {
  
  packetSize =Udp.parsePacket(); //Reads the packet size
  
  if(packetSize>0) { //if packetSize is >0, that means someone has sent a request
    
    Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE); //Read the data request
    String datReq(packetBuffer); //Convert char array packetBuffer into a string called datReq
    
    if (datReq =="Temperature") { //Do the following if Temperature is requested
    
      tempC = mySensor.readTemperature(); //Read the temperature
      tempF = tempC*1.8 + 32; //Convert temp to F
      
      Udp.beginPacket(Udp.remoteIP(), Udp.remotePort()); //Initialize packet send
      Udp.print(tempF); //Send the temperature data
      Udp.endPacket(); //End the packet
      
    }
    
    if (datReq== "Pressure") { //Do the following if Pressure is requested
    
      Pressure=mySensor.readPressure(); //read the pressure
      
        Udp.beginPacket(Udp.remoteIP(), Udp.remotePort()); //Initialize packet send
        Udp.print(Pressure); //Send the Pressure data
        Udp.endPacket(); //End the packet
        
    }
      
  }
  memset(packetBuffer, 0, UDP_TX_PACKET_MAX_SIZE); //clear out the packetBuffer array
}

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

#include <EthernetUdp.h> //Load the Udp Library

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

#include "Wire.h" //imports the wire library

#include "Adafruit_BMP085.h" // import the Pressure/Temperature sensor library

Adafruit_BMP085 mySensor; //Create a sensor object

float tempC; //Declare variable for Temp in C

float tempF; //Declare variable for Temp in F

float Pressure; //Declare a variable for Pressure

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

IPAddress ip(10, 1, 15, 243); //Assign the IP Adress

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

char packetBuffer[UDP_TX_PACKET_MAX_SIZE]; //dimensian a char array to hold our data packet

String datReq; //String for our data

int packetSize; //Size of the packet

EthernetUDP Udp; // Create a UDP Object

void setup() {

Serial.begin(9600); //Initialize Serial Port

Ethernet.begin( mac, ip); //Inialize the Ethernet

Udp.begin(localPort); //Initialize Udp

delay(1500); //delay

mySensor.begin(); //initialize pressure-temp sensor

}

void loop() {

packetSize =Udp.parsePacket(); //Reads the packet size

if(packetSize>0) { //if packetSize is >0, that means someone has sent a request

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

String datReq(packetBuffer); //Convert char array packetBuffer into a string called datReq

if (datReq =="Temperature") { //Do the following if Temperature is requested

tempC = mySensor.readTemperature(); //Read the temperature

tempF = tempC*1.8 + 32; //Convert temp to F

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

Udp.print(tempF); //Send the temperature data

Udp.endPacket(); //End the packet

}

if (datReq== "Pressure") { //Do the following if Pressure is requested

Pressure=mySensor.readPressure(); //read the pressure

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

Udp.print(Pressure); //Send the Pressure data

Udp.endPacket(); //End the packet

}

memset(packetBuffer, 0, UDP_TX_PACKET_MAX_SIZE); //clear out the packetBuffer array

}

Once you have this on your arduino, and the arduino connected to the internet via an Ethernet cable, you can test by opening a command line in Windows. Then ping the address you have assigned to the Arduino. If it pings correctly and you get a reply, you are ready to develop the Python code. The Python will be the client. It will send the requests to the Arduino, and the Arduino will respond with data. Since our circuit can measure pressure or temperature, you can request either of those. When the arduino receives a request for temperature, it will go out, make the temperature measurement and then return the data to Python. Similarly, if you request Pressure the arduino will read the request, will make the Pressure measurement, and then return pressure reading to the client (Python).

from socket import *
import time

address= ( '10.1.15.243', 5000) #define server IP and port
client_socket =socket(AF_INET, SOCK_DGRAM) #Set up the Socket
client_socket.settimeout(1) #Only wait 1 second for a response

while(1):

    data = "Temperature" #Set data request to Temperature

    client_socket.sendto( data, address) #Send the data request

    try:

        rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino
        temp = float(rec_data) #Convert string rec_data to float temp
        print "The Measured Temperature is ", temp, " degrees F." # Print the result

    except:
        pass

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

    data = "Pressure" #Set data request to Pressure

    client_socket.sendto( data, address) #Send the data request

    try:

        rec_data, addr = client_socket.recvfrom(2048) #Read response from arduino
        Pressure = float(rec_data) #Convert string rec_data to float temp
        print "The Measured Pressure is ", Pressure, " Pa." # Print the result

    except:
        pass

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

    print ""

from socket import *

import time

address= ( '10.1.15.243', 5000) #define server IP and port

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

client_socket.settimeout(1) #Only wait 1 second for a response

while(1):

data = "Temperature" #Set data request to Temperature

client_socket.sendto( data, address) #Send the data request

try:

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

temp = float(rec_data) #Convert string rec_data to float temp

print "The Measured Temperature is ", temp, " degrees F." # Print the result

except:

pass

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

data = "Pressure" #Set data request to Pressure

client_socket.sendto( data, address) #Send the data request

try:

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

Pressure = float(rec_data) #Convert string rec_data to float temp

print "The Measured Pressure is ", Pressure, " Pa." # Print the result

except:

pass

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

print ""

This python code will request Temperature, will then read the response, and then will print the data. It then requests Pressure, reads the response, and then prints it. If you look at our earlier lessons you can see graphical techniques to visually present the data. The hard part is getting the data passed back and forth, which we show how to do in this lesson.

Arduino with Python, Tutorial

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

April 3, 2015 admin

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.

Technology Tutorials

Tag Archives: Python

Raspberry Pi LInux LESSON 26: Controlling GPIO Pins in Python

Raspberry Pi Linux LESSON 24: Running Python on the Raspberry Pi

Python with Arduino LESSON 17: Sending and Receiving Data Over Ethernet

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

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

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