# Python with Arduino LESSON 8: Introduction to Graphing with Matplotlib

While it is cool to create 3D visuals using vPython to represent our data coming from arduino, sometimes we want to make more quantitative graphs and charts from the data. To do this, we need to learn how to create graphs in Python. We do this using the library Matplotlib. We learned how to install and download this library in Python with Arduino LESSON 7: If you have not installed the library yet, make sure to go back and do in as shown in LESSON 7.

With the library installed, we are ready to learn Matplotlib. The video takes you through an introductory tutorial with step-by-step instructions. The code below is a sample of how to plot a sin and cos wave. You can watch the video, and then play around with the parameters to become familiar with this library.

# Python with Arduino LESSON 7: Installing Matplotlib for Graphing

In this video we provide step-by-step instructions on how to install Matplotlib. Hopefully you have been following our lessons, and have already installed Python 2.7, the 32 bit version. If you stay on the same path as me as far as libraries and software versions, all my tutorials should work easily for you. In order for matplotlib to work, you need to have the numpy library installed. In Python with Arduino LESSON 2 we installed the vPython library. If you installed the vPython library, you already have numpy, as that was part of the vPython installation. If you have not already installed vPython, you should review that lesson now and do that.

If you are following my lessons and software versions, you will want to install this version, which should be towards the top of the page:

matplotlib-1.2.0.win32-py2.7.exe — Binary installer for 32-bit Windows, built using python.org’s 2.7 and Numpy 1.6.2

Once it is installed you can test things with this simple program, which should plot a sine wave.

# Python with Arduino LESSON 6: Installing PIP on Windows

In this series of lessons you have learned to send data from Arduino to Python, and then do some pretty cool things in Python. We have created little virtual worlds, and have done neat dynamic graphics. Unfortunately not all Python libraries are as easy to install as vPython and pySerial. Some are next to impossible to install. The good news is that there is a free program called PIP that will install just about any Python library very easily. We need to pause and install PIP. Many of the future lessons will require you to have PIP installed on your machine. Please follow along with me on the video, which shows you how to install PIP on your windows machine. These links will be useful. You can download pip at this link:

https://pip.pypa.io/en/latest/installing.html

Go to the section on PIP install as seen here:

C:\Python27

and

C:\Python27\Scripts

If you do not know exactly what I am saying, then watch the video for more detail.

Once you have these in your system path, you can test your PIP as follows.

Open a CMD box.

Type:

pip install -U pip

This asks pip to update itself. You should see it come up and indicate it is either up to date or is updating. This will tell you that you have the PIP installed correctly.

Your life with Python will now be much easier because your system now knows the path to both your Python program and your PIP installer.

# Python with Arduino LESSON 5: Finishing our Virtual Reality Example

This Lesson finishes the work that was begun in Python with Arduino LESSON 4. In that lesson we built the circuit and programmed the arduino to measure the distance to a target and the color of the target. The program then output that data to the serial port. In today’s lesson we will use python to read that data stream, and use the data to dynamically update a virtual world we create.

You will need to start with the work in LESSON 4 to get your circuit working, and your arduino programmed up. Once you have done that, you are ready to use Python to program up your virtual world. Remember you will need to have the pyserial and the vPython libraries loaded. We showed how to install the software in Python with Arduino LESSON 2.

In the video we will go through the process step-by-step to create a virtual world. The code we end up with is posted below. You should not copy and paste the code, but just glance at it if you get stuck. In the end, you should develop your own virtual world and just use mine as a guide if you need more help.

The video explains each line of the code.  Play around and tweak the values and see the effect on your virtual scene. Now your assignment is to take what you have learned here, and continue to expand your virtual world. Add objects to your virtual scene. Perhaps build an object for the breadboard, color sensor and arduino. I will give you several days to do this, and then when I come around for a project grade, I will want to see who has built the most impressive virtual scene. You should go well beyond the simple demonstration I have done here.

# Python with Arduino LESSON 4: Expanding your Virtual World

In this lesson we will expand the virtual world we created in Python with Arduino LESSON 3. We will be creating a virtual world that will track a simple scene in the real world. In this project, the virtual world will track both the position and the color of a target in the real world. This lesson requires that you have the Python software and libraries installed, which we explained in LESSON 2.

This Lesson will be a bit more involved, and I will take you through it step-by-step. I will need to break things into two parts. In today’s lesson we will cover the Arduino side. We will develop the software that will measure distance and color, and then send those numbers over the serial port. Then in tomorrows lesson, we will develop the Python software to create a really cool virtual graphic to display the data in a virtual world.

For this project you will need the HC-SR04 ultrasonic sensor, the TCS230 Color Sensor, the Arduino Microcontroller, and some male/female jumper wires to connect to the color sensor.

The Ultrasonic Sensor can be attached per the schematic below:

Detailed tutorial on using this sensor was described in Arduino LESSON 18, so we will not go through all the details of using the sensor here. Review that lesson if you need more help. Key point here is to connect it as seen in diagram above.

You will also need to connect up the Color Sensor.

#### Connecting the Color Sensor to the Arduino

###### Arduino Pin
S0GND
S15V
S2pin 7
S3pin 8
OUTpin 4
VCC5V
GNDGND

Use of the color sensor was described in detail in Arduino LESSON 15.  You should be able to develop to write the software yourself based on earlier lessons to make measurements from both the Color Sensor, and Ultrasonic Sensor, but if you get stuck, you can glance at my code below. Again, it is important for you to write your own code and not copy and paste mine. Mine is just a reference if you get stuck.

The key point to notice with this code is the print statements, summarized below:

Notice that we are printing  our color strengths and distance on one line separated by commas. It is important to note the order of the data. When we read this in Python, we will read it in as one line of text, and then we will parse it into its individual values. So, we must make note and remember the order the data is arranged in in this line.

Remember when you have your python program reading this data, you must have your serial monitor closed. For now though, run your program and look at the serial monitor to verify you are getting correct data in the expected format.

In the next Lesson, LESSON 5, we will build the Python program to create a virtual world from this data.