Several development tools are available: ESP_IDF: The official Espressif development tool. Includes a gcc compiler for the ESP8266 and the ESP32 Please see https://docs.espressif.com/projects/esp-idf/en/latest/ The Arduino IDENeeds extensions for these processors and the different CPU boards see: https://www.arduino.cc/en/Main/Software MicroPython see: https://micropython-docs-esp32.readthedocs.io/en/esp32_doc/

Flashing the code

esptool

• esptool is called from the Makefiles in ESP-IDF
• esptool is used when we upload code from the Arduino IDE to the processor flash
• esptool is used when the Micropython IDE uPyCraft
  
  installs Micropython onto the processor flash

We can however also execute esptool directly.

How to write a Micropython program?

First we need a Micropython interpreter!

You find the sources here:

https://github.com/micropython/micropython/

In the repository you find ports for the ESP8266 and the ESP32.

In order to compile the code you need the ESP-IDF and its cross compilers

The code compiles into a binary file (firmware-combined.bin) which contains a boot loader and the interpreter.

This binary must be uploaded and flashed.

For documentation of the ESP8266 port of Micropython look at

https://docs.micropython.org/en/latest/esp8266/tutorial/index.html

How to communicate with the Micropython interpreter?

We use a serial connection passing through the micro USB connection.

As soon as we connect the processor card to the PC we see the

UART bridge and a new device: dev/ttyUSB0 is created.

This device is used to communicate with the Micropython REPL.

You see the command prompt and you can interact with Micropython. But … how to upload scripts?

What is REPL?

The communication tools: minicom

You see the command prompt and you can interact with Micropython.

But … how to upload scripts?

The command line tool ampy

IDE for Micropython: uPyCraft

uPyCraft

uPyCraft is a rather complete Integrate Development Environment (IDE)

which lets you

• Access the REPL
  
  
• Create directories on the Micropython file system
  
  
• Upload scripts
  
  
• Syntax check scripts
  
  
• Run scripts
  
  
• Install Micropython on your processor board

Flashing Micropython

This has already been done for you! However, it is easy if you want to do it

at home with a new processor board.

Compiling a new version of Micropython is substantially harder but also perfectly possible.

uPyCraft(2)

uPyCraft is based on QT4 and is available for Linux, Windows and Mac.

It is written in PyQt4 the Python language binding to Qt4.

The Linux version did not work for me

I found a version based on PyQt5 (new version of QT) which was even worse.

I tried to correct as much as I could to make the PyQt5 version usable on Linux:

https://github.com/uraich/uPyCraft-Qt5

Thonny

Thonny (2)

Thonny is an IDE for Python which has provisions for Micropython.

Under Tools → Options button you can select the type of

Python interpreter you intend to use.

IoT Hello World program

A “Hello World” program, just printing “Hello World” on the screen

does not look very exciting.

However, this is generally used to verify that the infrastructure

Compiler, linker, downloader, flash program

are working correctly

In embedded systems printing can be quite complex

and a blinking LED is used instead.

Switching on and off a LED

The ESP8266 and the ESP32 have a “user LED” connected to GPIO 2.

How do we control this LED?

• Define that the LED is connected to GPIO 2
  
  
• Program this pin as output
  
  
• Write a logic 1 to the pin to switch it on
  
  
• Write a logic 0 to the pin to switch it off
  
  
• The logic state may be inverted if the LED is active low

Micropython hardware functions

The machine.Pin class

Switch the LED on, version 1

Switch the LED on, version 2

The blinking LED

Now we put the code into a script and run it

Changing the light intensity

The LED is connected to a digital line which can only be set to 0 or Vcc.

How can we change the light intensity and dim the LED?

The light intensity depends on the average current flowing through the LED.

The answer is PWM: pulse width modulation.

PWM in Micropython

Our PWM implementation

The WS2812B LED

A more complex LED:

• rgb LED used in LED chains.
  
  
• each ws18b12 contains the 3 colored LEDs and a controller.
  
  
• Can be cascaded and individually addressed, depending on its position in the chain
  
  
• Needs precise timing
  
  
• To use it we pass through the neopixel library built into MicroPython

WS2812B timing

For all the details on the ws2812b look at

https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf

24 bit of colour data puts 2e24 colours at your disposal

Coding of a single bit

The control word:

Cascading the WS2812B

Using the neopixel library

… and our code

We have a single neopixel connected to

GPIO pin 4 (ESP8266)

or

GPIO pin 21 (ESP32)

This code works on both CPUs!