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Practical Python Programming for IoT

You're reading from   Practical Python Programming for IoT Build advanced IoT projects using a Raspberry Pi 4, MQTT, RESTful APIs, WebSockets, and Python 3

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Product type Paperback
Published in Nov 2020
Publisher Packt
ISBN-13 9781838982461
Length 516 pages
Edition 1st Edition
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Author (1):
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Gary Smart Gary Smart
Author Profile Icon Gary Smart
Gary Smart
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Table of Contents (20) Chapters Close

Preface 1. Section 1: Programming with Python and the Raspberry Pi
2. Setting Up your Development Environment FREE CHAPTER 3. Getting Started with Python and IoT 4. Networking with RESTful APIs and Web Sockets Using Flask 5. Networking with MQTT, Python, and the Mosquitto MQTT Broker 6. Section 2: Practical Electronics for Interacting with the Physical World
7. Connecting Your Raspberry Pi to the Physical World 8. Electronics 101 for the Software Engineer 9. Section 3: IoT Playground - Practical Examples to Interact with the Physical World
10. Turning Things On and Off 11. Lights, Indicators, and Displaying Information 12. Measuring Temperature, Humidity, and Light Levels 13. Movement with Servos, Motors, and Steppers 14. Measuring Distance and Detecting Movement 15. Advanced IoT Programming Concepts - Threads, AsyncIO, and Event Loops 16. IoT Visualization and Automation Platforms 17. Tying It All Together - An IoT Christmas Tree 18. Assessments 19. Other Books You May Enjoy

Global variables

At line (3) in the following code snippet, we start with a few quasi-constants defining the maximum and minimum voltages we expect to receive through the analog input. When you ran the code previously, your end range voltages probably were not exactly 0 and 3.3 volts. This occurrence is expected, and it can make a program feel like the Pots do not reach the ends of their rotation. The value assigned to A_IN_EDGE_ADJ is used to compensate for this in code. We will revisit this variable in the next section:

A_IN_EDGE_ADJ = 0.002                     # (3)
MIN_A_IN_VOLTS = 0 + A_IN_EDGE_ADJ
MAX_A_IN_VOLTS = 3.3 - A_IN_EDGE_ADJ

Next, starting at line (4), we create two AnalogIn instances relating to the A0 and A1 inputs of the ADS1115 that are connected to our Pots. It's through these variables that we determine how much a user has rotated our frequency and duty cycle potentiometers:

frequency_ch = AnalogIn(ads, ADS.P0)  #ADS.P0 --> A0    # (4)
duty_cycle_ch = AnalogIn...
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