Read Sensor Data /w Python

How to Use Python to Read Sensor Data¶

Introduction¶

In this tutorial, we will show you how to read information off of an analog and digital sensor connected to an Arduino using Python. We will use the built-in Arduino Leonardo on the LattePanda and read off the digital PIR sensor data, as well as the data from an analog rotation sensor. Once you master this technique, you can play around with the code to read different signals off of different pins.

What You Need¶

Hardware

LattePanda
7-inch 1024 x 600 IPS Display for LattePanda
Mouse and Keyboard
Analog Rotation sensor, which can be found here.
Digital PIR Motion sensor, which can be found here.

Software

1.Arduino IDE

The latest software is available on the Arduino website. IDE stands for integrated development environment, and it allows programmers to develop software. Make sure to download the latest version of the Arduino IDE. We are using Arduino 1.8.5 in this example.

2.Python 2.7.15

This software is available on the python website. We have used python 2.7.15 in this example, which can be found here. We used the following installer to install the python IDE:

Please make sure when installing to select "add python.exe to Path" by clicking on the "Will be installed on local hard drive" option. This is shown below.

Once everything is ready we can start the process.

Step 1¶

Similar to the C# tutorial, we will need to upload the StandardFirmata code onto your local Arduino device. You can access the code by clicking File → Examples → Firmata → StandardFirmata, as shown below.

After the code appears, select the correct Arduino type and port as shown below.

Find the correct Arduino type

With the corresponding port

Once they have been selected, upload the code to your Arduino by clicking the arrow shown below.

Wait for the code to be uploaded.

Step 2¶

The next step is to install the firmata package by using the command prompt window. Make sure to right-click and run the command prompt as administrator.

After clicking this

This should appear

Type the following command in your command prompt window:

pip install pyFirmata

The following message will be shown if the installation is successful.

Step 3¶

Open IDLE Python to check whether the pyfirmata package has been installed correctly.

Enter the following command:

import pyfirmata

If no error message appears, it means that firmata has been successfully installed. Please refer to the picture below.

Everything is now ready for you to connect your sensor. The section below talks about reading information from an analog sensor. If you want to learn how to read information from the digital sensor, please refer to the corresponding guide that follows the analog sensor guide.

Analog Rotation Sensor¶

The Rotation Sensor is an Arduino-compatible multi-ring analog rotation sensor. It is based on the multi-turn precision potentiometer and is capable of ten full rotations. If the sensor input is 5V, then 5000mV will be divided into 3600 portions (10 rotations). When you adjust the rotation by 3 degrees, the voltage will have a resulting change of 2mV, so you can accurately alter the voltage with small changes. This can be easily connected to a LattePanda using a Gravity connection.

Connecting the Analog Rotation Sensor¶

Once the LattePanda has been set up, connect the rotation sensor to pin A0 (the 4^th pinhole on the left). Please refer to the LattePanda guide below.

Make sure the black cable is facing outside the LattePanda like this:

Analog Rotation Sensor Code¶

Create a new python file through the IDLE program and enter the following code. Change 'COM5' to the port that was shown on your device previously on Arduino. An iterator is required to make sure the loop continues and doesn't overflow when reading so many values. In order to print the value at the pin, it must be allowed to send values by enabling reporting. Pin(0) is used in this example, which is similar to the procedures before when we inserted the rotation sensor into pin A0.

Code:

from pyfirmata import Arduino, util
from pyfirmata.util import Iterator
import time
board = Arduino('COM5') #Select the correct port
it = util.Iterator(board)
it.start()
while True:
   board.analog[0].enable_reporting()
    print(board.analog[0].read())
   time.sleep(0.5)

The IDLE window should show the different values corresponding to the rotation sensor's readouts. The values should go up and down, between 0 and 1, as you turn the sensor. Feel free to play around with other analog sensors to read and write information to and from your Arduino. Here is a GIF on how the rotation sensor works. Enjoy!

Digital PIR Motion Sensor¶

The PIR sensors are designed to sense motion. They are small, inexpensive, energy-efficient, easy to use, and don't wear out. The PIR Sensor can detect infrared signals from the human body or other animals and is triggered by their movement, so it can be applied to a variety of scenarios which require motion detection. This new PIR sensor is smaller than the conventional ones, which makes it perfect for your Arduino projects! It can also be easily connected to your LattePanda using a Gravity connection.

Connecting the Digital PIR Sensor¶

Once the LattePanda has been set up, connect the PIR Motion to pin D9 (which is the 1^st pinhole on the left). Please refer to the LattePanda guide below.

Once again, make sure the black cable is facing outside the LattePanda like this:

Digital PIR Sensor Code¶

Create a new python file through the IDLE program and enter the following code. Change 'COM5' to the port that was shown on your device previously on Arduino. An iterator is required to make sure the loop continues and doesn't overflow when reading so many values. Pin(9) is used in this example, which is similar to the procedures before when we inserted the rotation sensor into pin D9.

Code:

from pyfirmata import Arduino, util

import time
board = Arduino('COM5') #Select the correct port
board.get_pin('d:9:i')
thread = util.Iterator(board)
thread.start()

time.sleep(1) 

while True:
    if board.digital[9].read()== True:
        print('!!!')
   else:
        print('No one')
   time.sleep(0.5)

The IDLE window should show a Boolean data type with either one of two values. This will either be true or false depending on whether motion has been detected. In the code, if motion is detected, the sensor will read 'True' and print out '!!!' as a warning, whereas if there is no motion detected, the sensor will continuously print 'No one'. Feel free to play around with other digital sensors to read and write information from your built-in Arduino. Here is a GIF on how the PIR Motion sensor works. Enjoy!

Additional Information¶

Attached is a PDF with some PyFirmata functions to use in Python that I have based some of my code on. Here is the PDF. Enjoy tinkering with your LattePanda's Arduino using Python!