Arduino 02: Using the Arduino with Python. Jeffrey A. Meunier University of Connecticut

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1 Arduino 02: Using the Arduino with Python Jeffrey A. Meunier University of Connecticut

2 About: How to use this document I designed this tutorial to be tall and narrow so that you can read it on one side of your screen while you follow along in the rest of the display area, like this: Tutorial work area Also, the pages in this tutorial are designed to be viewed as whole-page slides. I describe how to do that next. 2

3 Set your PDF viewer to single page mode (Mac) On a Mac, a PDF file will open in the Preview application by default. Hide the side bar and set it to Single Page. 3

4 Set your PDF viewer to single page mode (Windows) In Windows, a PDF file will open in the Reader application by default. You can open the menu from the icon in the upper left corner of the window and then choose Split Left or Split Right depending on your preference. Then right-click on the document and choose the One page viewing option. 4

5 Introduction In this document I show you how to get Python to communicate with your Arduino microcontroller board. This requires that you download a few files from my web site and install one standard module into Python. Ultimately, after all the initial setup is done, writing a Python program that uses the Arduino is not difficult at all. If you are an experienced Python programmer and Arduino user, you might want to jump ahead to see if the Summary and Appendix are all you need. 5

6 Objectives The objectives are: Installing a Python module with pip Downloading a Python module Writing a program in IDLE Communicating with the Arduino 6

7 Prerequisites Before proceeding with this tutorial Python must be installed on your computer. This tutorial shows examples using IDLE. You must also have installed firmware on the Arduino from a previous one of my tutorials. In this tutorial you will not need to use the Arduino application. 7

8 Outline These are the sections you'll go through in this exercise: 1. Install pyserial 2. Download the arduino.py module 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary 8

9 1. Install pyserial Introduction Python uses the USB connection to communicate with the Arduino. It needs to use the pyserial USB communications module, but this module isn't installed in Python by default. Here you will install that module, but how you install it depends on what computer you're using. 1. Your own Windows computer 2. Your own Mac or Linux computer 3. A computer in one of the UConn Learning Center labs 9

10 1. Install pyserial About pip If you are using your own computer then you will use the pip command to install the pyserial module in Python. The pip command is a recursive acronym (i.e., the acronym is part of the full name): PIP Installs Packages Recursive acronyms are common in computer science. Now skip to the page for your computer. It will have one of these logos in the corner: 10

11 1. Install pyserial with pip: Mac & Linux Open the Terminal application and enter the command: pip3 install pyserial Do not start Python first. You should see this in the Terminal window: The exact version number shown for the pyserial module might be different than what I show you, but it should show pyserial-x.x on the last line. Remember that your pip command is actually pip3. 11

12 1. Install pyserial with pip: Windows Open the cmd (Command Prompt) application and enter the command: pip install pyserial Do not start Python first. You should see this in the Command Prompt window: The exact version number shown for the pyserial module might be different than what I show you, but it should show pyserial-x.x on the last line. 12

13 1. Install pyserial: UConn Learning Center Download the pyserial.zip file from this web page: mware/index.html Save the file to your desktop. It should look like this: 13

14 1. Install pyserial: UConn Learning Center Double-click on the pyserial ZIP file to view its contents: Drag that serial folder onto the desktop. You may now delete the pyserial file from the desktop. 14

15 1. Install pyserial: UConn Learning Center Create a new folder for this project on your P: drive. Name the folder based on what course & project this is. CSE1010 / Lab n CSE1010 / Homework n Engr1166 / Project n Move the serial folder from the desktop into the folder you just created. 15

16 Outline These are the sections you'll go through in this exercise: 1. Install pyserial 2. Download the arduino.py module 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary 16

17 2. Download arduino.py Go to this web site: pport/index.html Right-click and save the arduino.py file: Save it in a new folder. Name the folder based on what course & project this is. CSE1010 / Lab n CSE1010 / Homework n Engr1166 / Project n Learning center students: put it in the same folder on your P: drive. 17

18 Outline These are the sections you'll go through in this exercise: 1. Install pyserial with pip 2. Download the arduino.pymodule 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary 18

19 3. Write a program in IDLE Motivation Here I have you write a program that doesn't have any actual Python statements in it, just a single comment line. The reason I have you do this is so that when you load the program into the Python Shell, it will make the folder you save it in the active folder. 19

20 3. Write a program in IDLE Open a new file Choose File New File from the Python Shell window. This will open a new text editor window in which you can write a Python program. Enter this single Python comment line in the text editor: # Arduino test program 1 20

3. Write a program in IDLE Save the file Press F5 in order to run the program in the Python Shell window. It will give you the message Source Must Be Saved, OK to Save? Press the OK button.

21 3. Write a program in IDLE Save the file Press F5 in order to run the program in the Python Shell window. It will give you the message Source Must Be Saved, OK to Save? Press the OK button. Navigate to the same folder where you saved the arduino.py file. Name this file test1.py, then save it. The Python Shell window moves to the foreground and becomes the active window. It should have a RESTART message in it: 21

22 Outline These are the sections you'll go through in this exercise: 1. Install pyserial with pip 2. Download the arduino.pymodule 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary 22

23 4. Enter Arduino commands First statement Here you will have Python send a few commands to the Arduino to switch the Arduino's on-board LED on and off. The commands will be entered into the Python Shell window. Enter the following statements into the Python Shell window. After each statement (in bold) I explain what the statement does. import arduino That command tells Python to import the arduino.py module file that you downloaded and saved already. Everything in that module immediately becomes available for your use in Python. 23

24 4. Enter Arduino commands Create Arduino instance a = arduino.arduino() That statement creates a new Arduino object in Python's memory and stores it in a variable called a. Explaining what it does and how it does it is beyond the scope of this tutorial. [Note that the thing in the variable a is an instance of the Arduino class that I wrote in the arduino.py module. If you're interested, have a look in that module to see how I implemented it.] 24

25 4. Enter Arduino commands Serial connection a.serialconnect() That statement causes Python to open a connection to the Arduino board over the USB cable, and stores the connection information inside the Arduino object stored in the variable a. If it worked correctly then you'll just see the Python prompt again. >>> However, you might see an error. (next slide) 25

26 4. Enter Arduino commands Serial connection error Traceback (most recent call last): File "<pyshell#6>", line 1, in <module> a.serialconnect()... Exception: No USB devices found If you see that error, then do the following: Ensure that your Arduino board is plugged into your computer. Ensure that the Arduino application is not running (i.e., exit out of it completely). Now try again! 26

27 4. Enter Arduino commands Still see the error? If you still get the error, then you should re-enter the a.serialconnect() statement but this time supply the name of the serial port as an argument. Remember in a previous tutorial when I asked you to write down the name of your serial port? This is where you're going to need it. Retype the command like this: a.serialconnect(your-port-name) Replace your-port-name with the name of your USB port, like for example '/dev/cu.usbmodem1411' (on a Mac) or 'COM7' (in Windows). Be sure to enclose it in quotes in order to make it a string. 27

28 4. Enter Arduino commands It should now be working I'll assume now that you got it working. For whatever project you do that uses the Arduino, you will need to do those first three statements only one time at the beginning of your program. import arduino a = arduino.arduino() a.serialconnect() 28

29 4. Enter Arduino commands It should now be working I'll assume now that you got it working. For whatever project you do that uses the Arduino, you will need to do those first three statements only one time at the beginning of your program. import arduino a = arduino.arduino() a.serialconnect() Many students forget these parentheses 29

30 4. Enter Arduino commands Set the pin mode Enter this next statement in Python: a.pinmode(13, 'o') That tells the Arduino that you're going to do output on pin number 13 of the Arduino. Each digital pin can do either input or output, but not at the same time. Use 'o' for output or 'i' for input. 30

31 4. Enter Arduino commands Turn the LED on a.digitalwrite(13, 1) Have a look at the Arduino board. A small red LED in the middle of the board should be glowing. (It might be a different color or in a different location if you're not using the RoboRED board.) Now enter this command: a.digitalwrite(13, 0) That turns the LED off. 31

32 4. Enter Arduino commands More commands At this point you may do as many digitalwrite, digitalread, analogwrite, or analogread statements as you like within your program. The statements are described in Appendix A of this document. 32

33 4. Enter Arduino commands Disconnect from USB a.serialdisconnect() That tells Python that you're finished using the Arduino board for now. It closes the USB connection between Python and the Arduino. In your own programs you need to do that statement only one time just before the program ends. 33

34 Outline These are the sections you'll go through in this exercise: 1. Install pyserial with pip 2. Download the arduino.pymodule 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary 34

35 5. Summary Ensure that my ArduinoFirmware file was the last file loaded onto the Arduino. You don't need to re-upoad it. Create a new folder. Copy the arduino.py module into that folder. Start IDLE, create a New File. import arduino a = arduino.arduino() a.serialconnect() # -> your program goes here # at end of program: a.serialdisconnect() 35

36 Outline These are the sections you'll go through in this exercise: 1. Install pyserial with pip 2. Download the arduino.pymodule 3. Write a new program in IDLE 4. Enter some Arduino commands 5. Summary You're done! 36

Arduino 04: Python Arduino reference. Jeffrey A. Meunier University of Connecticut

Arduino 04: Python Arduino reference Jeffrey A. Meunier jeffm@engr.uconn.edu University of Connecticut About: How to use this document I designed this tutorial to be tall and narrow so that you can read