HardwareAccessAndMicropython < AFNOG

Setting up and IoT

Session 2: Micropython and
Hardware access

Uli Raich
Formally CERN, Geneva, Switzerland

Slide 1 of 35

The WeMos D1 mini CPU card

ESP8266

cost: 2.21 Euros

ESP32

cost: 4.1o Euros

Slide 2 of 35

CPU Pinout


ESP8266	ESP32

Please note: The pin numbers IOxx on the ESP32 correspond

to the GPIO pin numbers

The pins in the white fields go to the WeMos D1 mini bus

and are also available on the ESP8266

The other pins are only accessible on the ESP32 CPU card

The pin numbers Dx do not correspond to GPIO pin numbers!

Please refer to the next slide for correspondence

Slide 3 of 35

CPU pinouts for reference

Slide 4 of 35

Meaning of pins on ESP8266

GPIO: General Purpose Input Output. Drives a single digital line which can be programmed input or output SCL/SDA: The I2C bus:a 2 wire bus interfacing sensors or actuators to the CPU SCL,MISO,MOSI,SS: SPI the Serial Peripheral Interface. Used fast communication with external device

GPIO: General Purpose Input Output.
Drives a single digital line which
can be programmed input or output

SCL/SDA: The I2C bus:a 2 wire bus
interfacing sensors or actuators to the CPU
SCL,MISO,MOSI,SS: SPI
the Serial Peripheral Interface.
Used fast communication with external device

Slide 5 of 35

Meaning of pins on ESP32

Slide 6 of 35

How to program the processor

	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/

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/

Slide 7 of 35

Flashing the code

Slide 8 of 35

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

In the above cases the use of esptool is hidden to us.

We can however also execute esptool directly.

Slide 9 of 35

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

Slide 10 of 35

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?

Slide 11 of 35

What is REPL?

Slide 12 of 35

The communication tools: minicom

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

But … how to upload scripts?

Slide 13 of 35

The command line tool ampy

Slide 14 of 35

IDE for Micropython: uPyCraft

Slide 15 of 35

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

Slide 16 of 35

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.

Slide 17 of 35

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

Slide 18 of 35

Thonny

Slide 19 of 35

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.

Slide 20 of 35

!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.

Slide 21 of 35

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

Slide 22 of 35

Micropython hardware functions

Slide 23 of 35

The machine.Pin class

Slide 24 of 35

Switch the LED on, version 1

Slide 25 of 35

Switch the LED on, version 2

Slide 26 of 35

The blinking LED

Now we put the code into a script and run it

Slide 27 of 35

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.

Slide 28 of 35

PWM in Micropython

Slide 29 of 35

Our PWM implementation

Slide 30 of 35

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

Slide 31 of 35

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:

Slide 32 of 35

Cascading the WS2812B

Slide 33 of 35

Using the neopixel library

Slide 34 of 35

… and our code

We have a single neopixel connected to

GPIO pin 4 (ESP8266)

GPIO pin 21 (ESP32)

This code works on both CPUs!

Slide 35 of 35

Uli Raich - 2019-05-13

Comments

I	Attachment	History	Action	Size	Date	Who
png	ws2812ControlWord.png	r1	manage	7.6 K	2019-05-14 - 12:42	UliRaich
png	ws2812Bits.png	r1	manage	11.9 K	2019-05-14 - 12:42	UliRaich
png	minicom.png	r1	manage	17.2 K	2019-05-14 - 11:42	UliRaich
png	ledControl1.png	r1	manage	19.8 K	2019-05-14 - 12:17	UliRaich
png	ledControl2.png	r1	manage	19.8 K	2019-05-14 - 12:18	UliRaich
png	pinControl2.png	r1	manage	19.8 K	2019-05-14 - 12:18	UliRaich
png	ws2812Chain.png	r1	manage	19.9 K	2019-05-14 - 12:42	UliRaich
png	repl.png	r1	manage	20.2 K	2019-05-14 - 11:45	UliRaich
png	pwm_uP.png	r1	manage	24.6 K	2019-05-14 - 12:31	UliRaich
png	updateFirmware.png	r1	manage	27.3 K	2019-05-14 - 11:59	UliRaich
png	thonny_uP.png	r1	manage	31.0 K	2019-05-14 - 12:05	UliRaich
png	cpuPinouts.png	r1	manage	34.1 K	2019-05-13 - 20:32	UliRaich
png	pwm.png	r1	manage	51.4 K	2019-05-14 - 12:27	UliRaich
png	lsusb.png	r1	manage	73.3 K	2019-05-14 - 11:48	UliRaich
png	blinkingLed.png	r1	manage	79.9 K	2019-05-14 - 12:17	UliRaich
png	neopixelCode.png	r1	manage	79.9 K	2019-05-14 - 12:46	UliRaich
png	ampy.png	r1	manage	100.7 K	2019-05-14 - 11:42	UliRaich
png	esp8266Programming.png	r1	manage	108.3 K	2019-05-14 - 09:59	UliRaich
png	esptool.png	r1	manage	114.3 K	2019-05-14 - 11:28	UliRaich
png	esp8266.png	r1	manage	116.1 K	2019-05-13 - 20:27	UliRaich
png	pwmImpl.png	r1	manage	116.7 K	2019-05-14 - 12:31	UliRaich
png	esp32-pinout-chip-ESP-WROOM-32.png	r1	manage	137.4 K	2019-05-14 - 09:50	UliRaich
png	thonny.png	r1	manage	148.1 K	2019-05-14 - 12:05	UliRaich
png	esp32Pinout-v2.png	r1	manage	151.2 K	2019-05-14 - 09:01	UliRaich
png	esp8266PinMeaning.png	r2 r1	manage	155.3 K	2019-05-14 - 09:43	UliRaich
png	hardwareFunctions.png	r1	manage	159.5 K	2019-05-14 - 12:17	UliRaich
png	pinClass.png	r1	manage	160.1 K	2019-05-14 - 12:20	UliRaich
png	uPyCraft.png	r1	manage	164.1 K	2019-05-14 - 11:43	UliRaich
png	neopixel.png	r1	manage	165.5 K	2019-05-14 - 12:46	UliRaich
png	esp8266Pinout.png	r1	manage	176.4 K	2019-05-13 - 20:41	UliRaich
png	wemosEsp32.png	r1	manage	213.3 K	2019-05-13 - 20:29	UliRaich
odp	afnog19-ws-session2.odp	r1	manage	6431.5 K	2019-05-14 - 09:01	UliRaich

This topic: AFNOG > WebHome > AFNOGWorkshop2019 > AFNOG-2019Slides > WorkshopSlides > HardwareAccessAndMicropython
Topic revision: r4 - 2019-05-14 - UliRaich

Session 2: Micropython andHardware accessUli RaichFormally CERN, Geneva, Switzerland

Comments

Session 2: Micropython and
Hardware access

Uli Raich
Formally CERN, Geneva, Switzerland