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

Transcription

1 Arduino 04: Python Arduino reference 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 This document lists the methods available in the arduino.py module and how they are used. 5

6 Prerequisites 1. The ArduinoFirmware-xxxx.xx.xx.ino file must have been uploaded to the Arduino board. 2. The arduino.py file must be present in the project folder. See the web page to download either of those files. See the previous tutorials for additional details about installing those files. 6

7 Importing the Arduino module import arduino 7

8 Creating an Arduino instance a = arduino.arduino() Here I use the variable a, but the variable name is arbitrary. Whatever variable name you use must be the variable name that you use when you prefix the remaining method calls, as in: a.serialconnect() 8

9 Connecting to the Arduino a.serialconnect() or a.serialconnect(portname) This opens the communications channel between Python and the Arduino board. If the method can't find your serial port and it reports an error message instead, then you may need to specify the name of the serial port when you call the method, like this: a.serialconnect('com6') 9

10 Guessing the serial port name a.guessserialport() This method is called automatically by the serialconnect method, so you don't need to call it yourself. Calling this method just returns the name of the port that Python thinks your Arduino is connected to. If Python isn't able to guess your serial port name correctly, then calling this method explicitly isn't going to help you. You need to determine the port name yourself and then provide that name as an argument when you call the serialconnect method. Nevertheless it can be useful to call this method to see what Python thinks the Arduino's serial port is. 10

11 Analog read a.analogread(pinnumber) This returns a number in the range 0 to Note that you probably want to store that return value in a variable. For example: brightness = a.analogread(3) 11

12 Analog write a.analogwrite(pinnumber, value) The value can be a number in the range 0 to

13 Digital read a.digitalread(pinnumber) This returns a 0 or a 1. Note that you probably want to store that return value in a variable. For example: pushbutton = a.digitalread(6) Also note that before you start reading the value of a digital pin you should set its mode to input: a.pinmode(pinnumber, 'i') Be aware that you need to set the mode of a digital pin only one time. After you set the mode to input, you can do a digital read of that pin as many times as you like. 13

14 Digital write a.digitalwrite(pinnumber, value) The value can be 0 or 1. Before you start writing the value of a digital pin you should set its mode to output: a.pinmode(pinnumber, 'o') Be aware that you need to set the mode of a digital pin only one time. After you set the mode to output, you can do a digital write of that pin as many times as you like. 14

15 Setting the pin mode a.pinmode(pinnumber, mode) The pinmode method applies only to digital pins, since each pin can be set to do either output or input. Analog pins are hard-wired: analog input is done on the analog input pins, and analog output is done on the PWM digital pins. 15

16 Disconnecting from the Arduino a.serialdisconnect() This closes the communications channel between Python and the Arduino. 16