PySerial Simulator

--D. Thiebaut (talk) 13:45, 21 April 2014 (EDT)

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The purpose of this tutorial is to illustrate the basic steps required to build a Python module that can be used as a PySerial replacement while developing a Python application that interfaces with an Arduino. The module presented here supports the basic PySerial functions one needs to call from a Python app to talk to an Arduino, but these functions either do not do anything, or returned canned, predefined data.

PySerial

The first examples of a real PySerial program are taken from http://pyserial.sourceforge.net/shortintro.html, and are reproduced below:

Example 1

>>> import serial
>>> ser = serial.Serial(0)  # open first serial port
>>> print ser.name          # check which port was really used
>>> ser.write("hello")      # write a string
>>> ser.close()             # close port

Example 2

>>> ser = serial.Serial('/dev/ttyS1', 19200, timeout=1)
>>> x = ser.read()          # read one byte
>>> s = ser.read(10)        # read up to ten bytes (timeout)
>>> line = ser.readline()   # read a '\n' terminated line
>>> ser.close()

Example 3

>>> ser = serial.Serial(1, 38400, timeout=0,
...                     parity=serial.PARITY_EVEN, rtscts=1)
>>> s = ser.read(100)       # read up to one hundred bytes
...                         # or as much is in the buffer

Example 4

>>> ser = serial.Serial()
>>> ser.baudrate = 19200
>>> ser.port = 0
>>> ser
Serial<id=0xa81c10, open=False>(port='COM1', baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0)
>>> ser.open()
>>> ser.isOpen()
True
>>> ser.close()
>>> ser.isOpen()
False

Implementing the Simulator Module

So, all we have to do is create a module called fakeSerial.py that will contain

1. a class called Serial() that can be initialized with various amount of arguments
2. a member variable of this class should be called name and return the name of a port (fictitius)
3. a method called write( ) which receives a string and passes it to the fake Arduino
4. a method called read() which will read some number of bytes from the Arduino
5. a method called close() that closes the port and make all further operations with the Arduino impossible.
6. a method called isOpen() which will return True or False depending on whether the port to the fake Arduino is opened or closed.

Below is our first attempt at building this module.