Ultrasonic Ranger

by Dan Peirce B.Sc.

reformated from dokuwiki on July 20, 2013

Python Program

The ultrasonic ranging module sends asynchronous serial data in the form of a "R" followed by three digits representing the range in inches followed by a carriage return. In the following program the carriage return is ignored (python looks for new line as a line delimiter; it does not use carriage return which is unfortunately what is sent by the sonic ranger).

I also have C code (for a PIC18LF2620 rather than for a PC).
See https://our.kwantlen.ca/personal/danp/Shared%20Documents/range_with_compa rator.zip (requires login to obtain the zip file -- I can't post it here at this time because it may become part of a class assignment).

import serial
import time

ser = serial.Serial(2)  # com1 is (0) -- com3 is (2)
print ser.portstr,      # prints the actual port name used
print 'Python range2.py'
print ' by Dan Peirce B.Sc.' 
print ' of Kwantlen Polytechnic University'

for j in range(1,15):  # just a python for loop (results in 14 iterations of the loop)
    ser.flushInput()   # The PC has a big buffer that could be full by now
    time.sleep(0.01)   # pause for 10 ms to allow some time for new data to arrive -- in hindsight I don't think this was needed
    s = ser.read(5)    # read the serial port in putting 5 characters into a string - I believe this blocks until 5chars have been received
    print s[:-1],      # print all but the last character of the string (the last character should be a carriage return)
    time.sleep(1)      # sleep for a second (don't want to update too fast as I want to have time to move the reflector)
#note that in python indenting creates a block like { } in c.


COM3 Python range2.py
 by Dan Peirce B.Sc.
 of Kwantlen Polytechnic University
R006 R006 R007 R009 R010 R011 R011 R012 R013 R013 R015 R017 R015 R020

Example Using Python and Tkinter

This example is for a different device (a three axis accelerometer) but it is quite easy to modify to be suitable for the MaxSonar module. It will produce a plot of data.

I may well go back a make new versions of the PIC program to use with a modified version of this python/tkinter program.

Using matplotlib

A different solution to creating plots is making use of the library matplotlib. This library was created to combine plotting capabilities similar to Matlab with the Python programming language.