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Micropython on Any Arduino Board?

Micropython on Any Arduino Board?

Post by yllumi » Mon May 04, 2015 8:30 am

Re: Micropython on Any Arduino Board?

Post by yllumi » Mon May 04, 2015 8:35 am

Re: Micropython on Any Arduino Board?

Post by pfalcon » Mon May 04, 2015 10:40 am

Re: Micropython on Any Arduino Board?

Post by Damien » Wed May 06, 2015 11:29 pm

Re: Micropython on Any Arduino Board?

Post by qubit » Sat Nov 07, 2015 10:10 pm

Not exactly Arduino but I am attempting to port the framework over to the Atmel M0 and M7 chips, partly because I use them and trying to give Atmel some more loving. Being a novice at this Micropython stuff I don’t expect my progress to be anything fast.

I have managed to build an image with no errors but no REPL on the USB or debug port. Just to clarify, is the bare-arm the best starting place for porting over to other ARM based (Atmel) MCUs?

Re: Micropython on Any Arduino Board?

Post by dhylands » Sat Nov 07, 2015 11:01 pm

bare-arm or minimal are probably reasonable places to start if going to a new family (i.e. not STM).

We have MicroPython running on the STM32F7DISC board which is using an M7 processor. But if you’re on a non-stm processor, then the peripherals will all be different.

Re: Micropython on Any Arduino Board?

Post by eerimoq » Mon Sep 26, 2016 5:54 pm

I’ve been working on a Programming Platform called Simba that is a C implementation of an RTOS and various drivers. A few weeks ago I stumbled upon MicroPython and was really impressed. I figured, hey, why not try to run MicroPython on top of my RTOS, and so I did.

I named it Pumbaa! =)

It supports the Arduino Due and can be installed using the Arduino IDE. Write the main frozen Python script in the sketch file. Pretty neat for the basic user!

Re: Micropython on Any Arduino Board?

Post by SpotlightKid » Tue Sep 27, 2016 9:31 am

Re: Micropython on Any Arduino Board?

Post by eerimoq » Tue Sep 27, 2016 7:17 pm

Simba is already ported to a few STM32Fx MCU:s.

Here is a list of MCU:s:

As of today, only pin and uart drivers are implemented for STM32Fx ports. The reason is that I seldom use STM32Fx myself and I find more joy in implementing other functionality (for example microPython on Simba) than those drivers. Simba and Pumbaa are my spare time projects and I want to enjoy working on them =)

Some information about the boards supported by Simba can be found in the documentation. It lists the drivers that are supoprted for the various boards, and hopefully the list is up to date.

So yes, it is feasible to Pumbaa to STM32Fx as well.

Источник

Getting Started with OpenMV and MicroPython

AUTHOR: Sebastian Romero, Benjamin DannegГҐrd

Overview

The OpenMV IDE is meant to provide an Arduino like experience for simple machine vision tasks using a camera sensor. In this tutorial, you will learn about some of the basic features of the OpenMV IDE and how to create a simple MicroPython script.

Goals

  • The basic features of the OpenMV IDE
  • How to create a simple MicroPython script
  • How to use the OpenMV IDE to run MicroPython on Portenta H7

Required Hardware and Software

  • Portenta H7 (ABX00042), Portenta H7 Lite (ABX00045) or Portenta H7 Lite Connected (ABX00046)
  • USB-C cable (either USB-A to USB-C or USB-C to USB-C)
  • Portenta Bootloader Version 20+
  • OpenMV IDE 2.6.4+

Instructions

Using the OpenMV IDE, you can run MicroPython scripts on the Portenta H7 board. MicroPython provides a lot of classes and modules that make it easy to quickly explore the features of the Portenta H7. In this tutorial, you will first download the OpenMV IDE and set up the development environment. Here you can read more about the OpenMV IDE. OpenMV comes with its own firmware that is built on MicroPython. You will then learn to write a simple script that will blink the on-board RGB LED using some basic MicroPython commands.

1. Downloading the OpenMV IDE

Before you can start programming OpenMV scripts for the Portenta, you need to download and install the OpenMV IDE.

IMPORTANT: Please make sure to update the bootloader to the most recent version to benefit from the latest improvements. Follow these steps before you proceed with the next step of this tutorial.

Open the OpenMV download page in your browser, download the version that you need for your operating system and follow the instructions of the installer.

2. Flashing the OpenMV Firmware

Connect the Portenta to your computer via the USB-C cable if you haven’t done so yet. Make sure you first update the bootloader to the latest version using the STM32H747_updateBootloader sketch in the examples menu in the Arduino IDE.

Instructions on how to update the bootloader can be found in the «Updating the Portenta Bootloader» tutorial.

After updating the bootloader put the Portenta in bootloader mode by double-pressing the reset button on the board. The built-in green LED will start fading in and out. Now open the OpenMV IDE.

The OpenMV IDE after starting it

Click on the «connect» symbol at the bottom of the left toolbar.

Click the connect button to attach the Portenta to the OpenMV IDE

A pop-up will ask you how you would like to proceed. Select «Reset Firmware to Release Version». This will install the latest OpenMV firmware on the Portenta H7. You can leave the option of erasing the internal file system unselected and click «OK».

Install the latest version of the OpenMV firmware

Portenta H7’s green LED will start flashing while the OpenMV firmware is being uploaded to the board. A terminal window will open and show you the flashing progress. Wait until the green LED stops flashing and fading. You will see a message saying «DFU firmware update complete!» when the process is done.

Installing firmware on portenta board in OpenMV

Installing the OpenMV firmware will overwrite any existing sketches in the internal Flash of Portenta H7. Also the M7 port will not be exposed in the Arduino IDE anymore. To re-flash the M7 with an Arduino firmware you need to put the board into bootloader mode. To do so, double press the reset button on the Portenta H7 board. The built-in green LED will start fading in and out. In bootloader mode you will see the Portenta M7 port again in the Arduino IDE.

The board will start flashing its blue LED when it is ready to be connected. After confirming the completion dialog, the Portenta H7 should already be connected to the OpenMV IDE, otherwise click the «connect» button (plug symbol) once again.

When the Portenta H7 is successfully connected a green play button appears

3. Preparing the Script

Create a new script by clicking the «New File» button in the toolbar on the left side. Import the required module :

A module in Python is a confined bundle of functionality. By importing it into the script, it gets made available. For this example, you only need , which is a module that contains board related functionality such as PIN handling. You can read more about its functions here.

Now you can create the variables that will control our built-in RGB LED. With you can easily control each color.

Now you can easily distinguish between which color we control in the script.

4. Creating the Main Loop in the Script

Putting your code inside a while loop will make the code run continuously. In the loop you can turn on an LED with , then you can use the function to create a delay. This function will wait with execution of the next instruction in the script. The duration of the delay can be controlled by changing the value inside the parentheses. The number defines how many milliseconds the board will wait. After the specified time has passed, you can turn off the LED with the function. You can repeat that for each color.

5. Uploading the Script

Here you can see the complete blink script:

Connect your board to the OpenMV IDE and upload the above script by pressing the play button in the lower left corner.

Press the green play button to upload the script

Now the built-in LED on your Portenta board should be blinking red, green and then blue repeatedly.

Conclusion

In this tutorial you learned how to use the OpenMV IDE with your Portenta board. You also learned how to control the Portenta H7’s RGB LED with MicroPython functions and to upload the script to your board using the OpenMV IDE.

Источник

Arduino With Python: How to Get Started

Table of Contents

Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: Arduino With Python: How to Get Started

Microcontrollers have been around for a long time, and they’re used in everything from complex machinery to common household appliances. However, working with them has traditionally been reserved for those with formal technical training, such as technicians and electrical engineers. The emergence of Arduino has made electronic application design much more accessible to all developers. In this tutorial, you’ll discover how to use Arduino with Python to develop your own electronic projects.

You’ll cover the basics of Arduino with Python and learn how to:

  • Set up electronic circuits
  • Set up the Firmata protocol on Arduino
  • Write basic applications for Arduino in Python
  • Control analog and digital inputs and outputs
  • Integrate Arduino sensors and switches with higher-level apps
  • Trigger notifications on your PC and send emails using Arduino

Free Bonus: 5 Thoughts On Python Mastery, a free course for Python developers that shows you the roadmap and the mindset you’ll need to take your Python skills to the next level.

The Arduino Platform

Arduino is an open-source platform composed of hardware and software that allows for the rapid development of interactive electronics projects. The emergence of Arduino drew the attention of professionals from many different industries, contributing to the start of the Maker Movement.

With the growing popularity of the Maker Movement and the concept of the Internet of Things, Arduino has become one of the main platforms for electronic prototyping and the development of MVPs.

Arduino uses its own programming language, which is similar to C++. However, it’s possible to use Arduino with Python or another high-level programming language. In fact, platforms like Arduino work well with Python, especially for applications that require integration with sensors and other physical devices.

All in all, Arduino and Python can facilitate an effective learning environment that encourages developers to get into electronics design. If you already know the basics of Python, then you’ll be able to get started with Arduino by using Python to control it.

The Arduino platform includes both hardware and software products. In this tutorial, you’ll use Arduino hardware and Python software to learn about basic circuits, as well as digital and analog inputs and outputs.

Arduino Hardware

To run the examples, you’ll need to assemble the circuits by hooking up electronic components. You can generally find these items at electronic component stores or in good Arduino starter kits. You’ll need:

  1. An Arduino Uno or other compatible board
  2. A standard LED of any color
  3. A push button
  4. A 10 KOhm potentiometer
  5. A 470 Ohm resistor
  6. A 10 KOhm resistor
  7. A breadboard
  8. Jumper wires of various colors and sizes

Let’s take a closer look at a few of these components.

Component 1 is an Arduino Uno or other compatible board. Arduino is a project that includes many boards and modules for different purposes, and Arduino Uno is the most basic among these. It’s also the most used and most documented board of the whole Arduino family, so it’s a great choice for developers who are just getting started with electronics.

Note: Arduino is an open hardware platform, so there are many other vendors who sell compatible boards that could be used to run the examples you see here. In this tutorial, you’ll learn how to use the Arduino Uno.

Components 5 and 6 are resistors. Most resistors are identified by colored stripes according to a color code. In general, the first three colors represent the value of a resistor, while the fourth color represents its tolerance. For a 470 Ohm resistor, the first three colors are yellow, violet, and brown. For a 10 KOhm resistor, the first three colors are brown, black, and orange.

Component 7 is a breadboard, which you use to hook up all the other components and assemble the circuits. While a breadboard is not required, it’s recommended that you get one if you intend to begin working with Arduino.

Arduino Software

In addition to these hardware components, you’ll need to install some software. The platform includes the Arduino IDE, an Integrated Development Environment for programming Arduino devices, among other online tools.

Arduino was designed to allow you to program the boards with little difficulty. In general, you’ll follow these steps:

  1. Connect the board to your PC
  2. Install and open the Arduino IDE
  3. Configure the board settings
  4. Write the code
  5. Press a button on the IDE to upload the program to the board

To install the Arduino IDE on your computer, download the appropriate version for your operating system from the Arduino website. Check the documentation for installation instructions:

  • If you’re using Windows, then use the Windows installer to ensure you download the necessary drivers for using Arduino on Windows. Check the Arduino documentation for more details.
  • If you’re using Linux, then you may have to add your user to some groups in order to use the serial port to program Arduino. This process is described in the Arduino install guide for Linux.
  • If you’re using macOS, then you can install Arduino IDE by following the Arduino install guide for OS X.

Note: You’ll be using the Arduino IDE in this tutorial, but Arduino also provides a web editor that will let you program Arduino boards using the browser.

Now that you’ve installed the Arduino IDE and gathered all the necessary components, you’re ready to get started with Arduino! Next, you’ll upload a “Hello, World!” program to your board.

“Hello, World!” With Arduino

The Arduino IDE comes with several example sketches you can use to learn the basics of Arduino. A sketch is the term you use for a program that you can upload to a board. Since the Arduino Uno doesn’t have an attached display, you’ll need a way to see the physical output from your program. You’ll use the Blink example sketch to make a built-in LED on the Arduino board blink.

To get started, connect the Arduino board to your PC using a USB cable and start the Arduino IDE. To open the Blink example sketch, access the File menu and select Examples, then 01.Basics and, finally, Blink:

The Blink example code will be loaded into a new IDE window. But before you can upload the sketch to the board, you’ll need to configure the IDE by selecting your board and its connected port.

To configure the board, access the Tools menu and then Board. For Arduino Uno, you should select Arduino/Genuino Uno:

After you select the board, you have to set the appropriate port. Access the Tools menu again, and this time select Port:

The names of the ports may be different, depending on your operating system. In Windows, the ports will be named COM4 , COM5 , or something similar. In macOS or Linux, you may see something like /dev/ttyACM0 or /dev/ttyUSB0 . If you have any problems setting the port, then take a look at the Arduino Troubleshooting Page.

After you’ve configured the board and port, you’re all set to upload the sketch to your Arduino. To do that, you just have to press the Upload button in the IDE toolbar:

When you press Upload, the IDE compiles the sketch and uploads it to your board. If you want to check for errors, then you can press Verify before Upload, which will only compile your sketch.

The USB cable provides a serial connection to both upload the program and power the Arduino board. During the upload, you’ll see LEDs flashing on the board. After a few seconds, the uploaded program will run, and you’ll see an LED light blink once every second:

After the upload is finished, the USB cable will continue to power the Arduino board. The program is stored in flash memory on the Arduino microcontroller. You can also use a battery or other external power supply to run the application without a USB cable.

Connecting External Components

In the previous section, you used an LED that was already present on the Arduino board. However, in most practical projects you’ll need to connect external components to the board. To make these connections, Arduino has several pins of different types:

Although these connections are commonly called pins, you can see that they’re not exactly physical pins. Rather, the pins are holes in a socket to which you can connect jumper wires. In the figure above, you can see different groups of pins:

  • Orange rectangle: These are 13 digital pins that you can use as inputs or outputs. They’re only meant to work with digital signals, which have 2 different levels:
    1. Level 0: represented by the voltage 0V
    2. Level 1: represented by the voltage 5V
  • Green rectangle: These are 6 analog pins that you can use as analog inputs. They’re meant to work with an arbitrary voltage between 0V and 5V.
  • Blue rectangle: These are 5 power pins. They’re mainly used for powering external components.

To get started using external components, you’ll connect an external LED to run the Blink example sketch. The built-in LED is connected to digital pin #13. So, let’s connect an external LED to that pin and check if it blinks. (A standard LED is one of the components you saw listed earlier.)

Before you connect anything to the Arduino board, it’s good practice to disconnect it from the computer. With the USB cable unplugged, you’ll be able to connect the LED to your board:

Note that the figure shows the board with the digital pins now facing you.

Using a Breadboard

Electronic circuit projects usually involve testing several ideas, with you adding new components and making adjustments as you go. However, it can be tricky to connect components directly, especially if the circuit is large.

To facilitate prototyping, you can use a breadboard to connect the components. This is a device with several holes that are connected in a particular way so that you can easily connect components using jumper wires:

You can see which holes are interconnected by looking at the colored lines. You’ll use the holes on the sides of the breadboard to power the circuit:

  • Connect one hole on the red line to the power source.
  • Connect one hole on the blue line to the ground.

Then, you can easily connect components to the power source or the ground by simply using the other holes on the red and blue lines. The holes in the middle of the breadboard are connected as indicated by the colors. You’ll use these to make connections between the components of the circuit. These two internal sections are separated by a small depression, over which you can connect integrated circuits (ICs).

You can use a breadboard to assemble the circuit used in the Blink example sketch:

For this circuit, it’s important to note that the LED must be connected according to its polarity or it won’t work. The positive terminal of the LED is called the anode and is generally the longer one. The negative terminal is called the cathode and is shorter. If you’re using a recovered component, then you can also identify the terminals by looking for a flat side on the LED itself. This will indicate the position of the negative terminal.

When you connect an LED to an Arduino pin, you’ll always need a resistor to limit its current and avoid burning out the LED prematurely. Here, you use a 470 Ohm resistor to do this. You can follow the connections and check that the circuit is the same:

  • The resistor is connected to digital pin 13 on the Arduino board.
  • The LED anode is connected to the other terminal of the resistor.
  • The LED cathode is connected to the ground (GND) via the blue line of holes.

For a more detailed explanation, check out How to Use a Breadboard.

After you finish the connection, plug the Arduino back into the PC and re-run the Blink sketch:

As both LEDs are connected to digital pin 13, they blink together when the sketch is running.

“Hello, World!” With Arduino and Python

In the previous section, you uploaded the Blink sketch to your Arduino board. Arduino sketches are written in a language similar to C++ and are compiled and recorded on the flash memory of the microcontroller when you press Upload. While you can use another language to directly program the Arduino microcontroller, it’s not a trivial task!

However, there are some approaches you can take to use Arduino with Python or other languages. One idea is to run the main program on a PC and use the serial connection to communicate with Arduino through the USB cable. The sketch would be responsible for reading the inputs, sending the information to the PC, and getting updates from the PC to update the Arduino outputs.

To control Arduino from the PC, you’d have to design a protocol for the communication between the PC and Arduino. For example, you could consider a protocol with messages like the following:

  • VALUE OF PIN 13 IS HIGH: used to tell the PC about the status of digital input pins
  • SET PIN 11 LOW: used to tell Arduino to set the states of the output pins

With the protocol defined, you could write an Arduino sketch to send messages to the PC and update the states of the pins according to the protocol. On the PC, you could write a program to control the Arduino through a serial connection, based on the protocol you’ve designed. For this, you can use whatever language and libraries you prefer, such as Python and the PySerial library.

Fortunately, there are standard protocols to do all this! Firmata is one of them. This protocol establishes a serial communication format that allows you to read digital and analog inputs, as well as send information to digital and analog outputs.

The Arduino IDE includes ready-made sketches that will drive Arduino through Python with the Firmata protocol. On the PC side, there are implementations of the protocol in several languages, including Python. To get started with Firmata, let’s use it to implement a “Hello, World!” program.

Uploading the Firmata Sketch

Before you write your Python program to drive Arduino, you have to upload the Firmata sketch so that you can use that protocol to control the board. The sketch is available in the Arduino IDE’s built-in examples. To open it, access the File menu, then Examples, followed by Firmata, and finally StandardFirmata:

The sketch will be loaded into a new IDE window. To upload it to the Arduino, you can follow the same steps you did before:

  1. Plug the USB cable into the PC.
  2. Select the appropriate board and port on the IDE.
  3. Press Upload.

After the upload is finished, you won’t notice any activity on the Arduino. To control it, you still need a program that can communicate with the board through the serial connection. To work with the Firmata protocol in Python, you’ll need the pyFirmata package, which you can install with pip :

After the installation finishes, you can run an equivalent Blink application using Python and Firmata:

Here’s how this program works. You import pyfirmata and use it to establish a serial connection with the Arduino board, which is represented by the board object in line 4. You also configure the port in this line by passing an argument to pyfirmata.Arduino() . You can use the Arduino IDE to find the port.

board.digital is a list whose elements represent the digital pins of the Arduino. These elements have the methods read() and write() , which will read and write the state of the pins. Like most embedded device programs, this program mainly consists of an infinite loop:

  • In line 7, digital pin 13 is turned on, which turns the LED on for one second.
  • In line 9, this pin is turned off, which turns the LED off for one second.

Now that you know the basics of how to control an Arduino with Python, let’s go through some applications to interact with its inputs and outputs.

Reading Digital Inputs

Digital inputs can have only two possible values. In a circuit, each of these values is represented by a different voltage. The table below shows the digital input representation for a standard Arduino Uno board:

Value Level Voltage
0 Low 0V
1 High 5V

To control the LED, you’ll use a push button to send digital input values to the Arduino. The button should send 0V to the board when it’s released and 5V to the board when it’s pressed. The figure below shows how to connect the button to the Arduino board:

You may notice that the LED is connected to the Arduino on digital pin 13, just like before. Digital pin 10 is used as a digital input. To connect the push button, you have to use the 10 KOhm resistor, which acts as a pull down in this circuit. A pull down resistor ensures that the digital input gets 0V when the button is released.

When you release the button, you open the connection between the two wires on the button. Since there’s no current flowing through the resistor, pin 10 just connects to the ground (GND). The digital input gets 0V, which represents the 0 (or low) state. When you press the button, you apply 5V to both the resistor and the digital input. A current flows through the resistor and the digital input gets 5V, which represents the 1 (or high) state.

You can use a breadboard to assemble the above circuit as well:

Now that you’ve assembled the circuit, you have to run a program on the PC to control it using Firmata. This program will turn on the LED, based on the state of the push button:

Let’s walk through this program:

  • Lines 1 and 2import pyfirmata and time .
  • Line 4 uses pyfirmata.Arduino() to set the connection with the Arduino board.
  • Line 6 assigns an iterator that will be used to read the status of the inputs of the circuit.
  • Line 7 starts the iterator, which keeps a loop running in parallel with your main code. The loop executes board.iterate() to update the input values obtained from the Arduino board.
  • Line 9 sets pin 10 as a digital input with pyfirmata.INPUT . This is necessary since the default configuration is to use digital pins as outputs.
  • Line 11 starts an infinite while loop. This loop reads the status of the input pin, stores it in sw , and uses this value to turn the LED on or off by changing the value of pin 13.
  • Line 17 waits 0.1 seconds between iterations of the while loop. This isn’t strictly necessary, but it’s a nice trick to avoid overloading the CPU, which reaches 100% load when there isn’t a wait command in the loop.

pyfirmata also offers a more compact syntax to work with input and output pins. This may be a good option for when you’re working with several pins. You can rewrite the previous program to have more compact syntax:

In this version, you use board.get_pin() to create two objects. digital_input represents the digital input state, and led represents the LED state. When you run this method, you have to pass a string argument composed of three elements separated by colons:

  1. The type of the pin ( a for analog or d for digital)
  2. The number of the pin
  3. The mode of the pin ( i for input or o for output)

Since digital_input is a digital input using pin 10, you pass the argument ‘d:10:i’ . The LED state is set to a digital output using pin 13, so the led argument is ‘d:13:o’ .

When you use board.get_pin() , there’s no need to explicitly set up pin 10 as an input like you did before with pyfirmata.INPUT . After the pins are set, you can access the status of a digital input pin using read() , and set the status of a digital output pin with write() .

Digital inputs are widely used in electronics projects. Several sensors provide digital signals, like presence or door sensors, that can be used as inputs to your circuits. However, there are some cases where you’ll need to measure analog values, such as distance or physical quantities. In the next section, you’ll see how to read analog inputs using Arduino with Python.

Reading Analog Inputs

In contrast to digital inputs, which can only be on or off, analog inputs are used to read values in some range. On the Arduino Uno, the voltage to an analog input ranges from 0V to 5V. Appropriate sensors are used to measure physical quantities, such as distances. These sensors are responsible for encoding these physical quantities in the proper voltage range so they can be read by the Arduino.

To read an analog voltage, the Arduino uses an analog-to-digital converter (ADC), which converts the input voltage to a digital number with a fixed number of bits. This determines the resolution of the conversion. The Arduino Uno uses a 10-bit ADC and can determine 1024 different voltage levels.

The voltage range for an analog input is encoded to numbers ranging from 0 to 1023. When 0V is applied, the Arduino encodes it to the number 0. When 5V is applied, the encoded number is 1023. All intermediate voltage values are proportionally encoded.

A potentiometer is a variable resistor that you can use to set the voltage applied to an Arduino analog input. You’ll connect it to an analog input to control the frequency of a blinking LED:

In this circuit, the LED is set up just as before. The end terminals of the potentiometer are connected to ground (GND) and 5V pins. This way, the central terminal (the cursor) can have any voltage in the 0V to 5V range depending on its position, which is connected to the Arduino on analog pin A0.

Using a breadboard, you can assemble this circuit as follows:

Before you control the LED, you can use the circuit to check the different values the Arduino reads, based on the position of the potentiometer. To do this, run the following program on your PC:

In line 8, you set up analog_input as the analog A0 input pin with the argument ‘a:0:i’ . Inside the infinite while loop, you read this value, store it in analog_value , and display the output to the console with print() . When you move the potentiometer while the program runs, you should output similar to this:

The printed values change, ranging from 0 when the position of the potentiometer is on one end to 1 when it’s on the other end. Note that these are float values, which may require conversion depending on the application.

To change the frequency of the blinking LED, you can use the analog_value to control how long the LED will be kept on or off:

Here, you calculate delay as analog_value + 0.01 to avoid having delay equal to zero. Otherwise, it’s common to get an analog_value of None during the first few iterations. To avoid getting an error when running the program, you use a conditional in line 13 to test whether analog_value is None . Then you control the period of the blinking LED.

Try running the program and changing the position of the potentiometer. You’ll notice the frequency of the blinking LED changes:

By now, you’ve seen how to use digital inputs, digital outputs, and analog inputs on your circuits. In the next section, you’ll see how to use analog outputs.

Using Analog Outputs

In some cases, it’s necessary to have an analog output to drive a device that requires an analog signal. Arduino doesn’t include a real analog output, one where the voltage could be set to any value in a certain range. However, Arduino does include several Pulse Width Modulation (PWM) outputs.

PWM is a modulation technique in which a digital output is used to generate a signal with variable power. To do this, it uses a digital signal of constant frequency, in which the duty cycle is changed according to the desired power. The duty cycle represents the fraction of the period in which the signal is set to high.

Not all Arduino digital pins can be used as PWM outputs. The ones that can be are identified by a tilde (

Several devices are designed to be driven by PWM signals, including some motors. It’s even possible to obtain a real analog signal from the PWM signal if you use analog filters. In the previous example, you used a digital output to turn an LED light on or off. In this section, you’ll use PWM to control the brightness of an LED, according to the value of an analog input given by a potentiometer.

When a PWM signal is applied to an LED, its brightness varies according to the duty cycle of the PWM signal. You’re going to use the following circuit:

This circuit is identical to the one used in the previous section to test the analog input, except for one difference. Since it’s not possible to use PWM with pin 13, the digital output pin used for the LED is pin 11.

You can use a breadboard to assemble the circuit as follows:

With the circuit assembled, you can control the LED using PWM with the following program:

There are a few differences from the programs you’ve used previously:

  1. In line 10, you set led to PWM mode by passing the argument ‘d:11:p’ .
  2. In line 15, you call led.write() with analog_value as an argument. This is a value between 0 and 1, read from the analog input.

Here you can see the LED behavior when the potentiometer is moved:

To show the changes in the duty cycle, an oscilloscope is plugged into pin 11. When the potentiometer is in its zero position, you can see the LED is turned off, as pin 11 has 0V on its output. As you turn the potentiometer, the LED gets brighter as the PWM duty cycle increases. When you turn the potentiometer all the way, the duty cycle reaches 100%. The LED is turned on continuously at maximum brightness.

With this example, you’ve covered the basics of using an Arduino and its digital and analog inputs and outputs. In the next section, you’ll see an application for using Arduino with Python to drive events on the PC.

Using a Sensor to Trigger a Notification

Firmata is a nice way to get started with Arduino with Python, but the need for a PC or other device to run the application can be costly, and this approach may not be practical in some cases. However, when it’s necessary to collect data and send it to a PC using external sensors, Arduino and Firmata make a good combination.

In this section, you’ll use a push button connected to your Arduino to mimic a digital sensor and trigger a notification on your machine. For a more practical application, you can think of the push button as a door sensor that will trigger an alarm notification, for example.

To display the notification on the PC, you’re going to use Tkinter, the standard Python GUI toolkit. This will show a message box when you press the button. For an in-depth intro to Tkinter, check out Python GUI Programming With Tkinter.

You’ll need to assemble the same circuit that you used in the digital input example:

After you assemble the circuit, use the following program to trigger the notifications:

This program is similar to the one used in the digital input example, with a few changes:

  • Lines 3 and 4 import libraries needed to set up Tkinter.
  • Line 6 creates Tkinter’s main window.
  • Line 7 tells Tkinter not to show the main window on the screen. For this example, you only need to see the message box.
  • Line 17 starts the while loop:
    1. When you press the button, the LED will turn on and messagebox.showinfo() displays a message box.
    2. The loop pauses until the user presses OK. This way, the LED remains on as long as the message is on the screen.
    3. After the user presses OK, root.update() clears the message box from the screen and the LED is turned off.

To extend the notification example, you could even use the push button to send an email when pressed:

You can learn more about send_email() in Sending Emails With Python. Here, you configure the function with email server credentials, which will be used to send the email.

Note: If you use a Gmail account to send the emails, then you need to enable the Allow less secure apps option. For more information on how to do this, check out Sending Emails With Python.

With these example applications, you’ve seen how to use Firmata to interact with more complex Python applications. Firmata lets you use any sensor attached to the Arduino to obtain data for your application. Then you can process the data and make decisions within the main application. You can even use Firmata to send data to Arduino outputs, controlling switches or PWM devices.

If you’re interested in using Firmata to interact with more complex applications, then try out some of these projects:

  • A temperature monitor to alert you when the temperature gets too high or low
  • An analog light sensor that can sense when a light bulb is burned out
  • A water sensor that can automatically turn on the sprinklers when the ground is too dry

Conclusion

Microcontroller platforms are on the rise, thanks to the growing popularity of the Maker Movement and the Internet of Things. Platforms like Arduino are receiving a lot of attention in particular, as they allow developers just like you to use their skills and dive into electronic projects.

You learned how to:

  • Develop applications with Arduino and Python
  • Use the Firmata protocol
  • Control analog and digital inputs and outputs
  • Integrate sensors with higher-level Python applications

You also saw how Firmata may be a very interesting alternative for projects that demand a PC and depend on sensor data. Plus, it’s an easy way to get started with Arduino if you already know Python!

Further Reading

Now that you know the basics of controlling Arduino with Python, you can start working on more complex applications. There are several tutorials that can help you develop integrated projects. Here are a few ideas:

REST APIs: These are widely used to integrate different applications. You could use REST with Arduino to build APIs that get information from sensors and send commands to actuators. To learn about REST APIs, check out Python REST APIs With Flask, Connexion, and SQLAlchemy.

Alternate GUIs: In this tutorial, you used Tkinter to build a graphical application. However, there are other graphical libraries for desktop applications. To see an alternative, check out How to Build a Python GUI Application With wxPython.

Threading: The infinite while loop that you used in this tutorial is a very common feature of Arduino applications. However, using a thread to run the main loop will allow you to execute other tasks concurrently. To learn how to use threads, check out An Intro to Threading in Python.

Face Detection: It’s common for IoT apps to integrate machine learning and computer vision algorithms. With these, you could build an alarm that triggers a notification when it detects faces on a camera, for example. To learn more about facial recognition systems, check out Traditional Face Detection With Python.

Lastly, there are other ways of using Python in microcontrollers besides Firmata and Arduino:

pySerial: Arduino Uno cannot run Python directly, but you could design your own Arduino sketch and use pySerial to establish a serial connection. Then you can control Arduino with Python using your own protocol.

MicroPython: If you’re interested in running Python directly on a microcontroller, then check out the MicroPython project. It provides an efficient implementation of Python to be executed on some microcontrollers such as the ESP8266 and ESP32.

SBCs: Another option is to use a single board computer (SBC) such as a Raspberry Pi to run Python. SBCs are complete, Arduino-sized computers that can run a Linux-based operating system, allowing you to use vanilla Python. As most SBCs provide General-purpose input and output pins, you can use it to replace an Arduino on most applications.

Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: Arduino With Python: How to Get Started

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About Renato Candido

Researcher in digital signal processing, telecommunications and machine learning. enthusiast.

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