Program all the thingsHow to develop IoT devices using

MicroPython

Anna Gerber

About me

• Senior Backend Developer at Console Connect (Node.js)

• Teach coding and robotics workshops and classes

• Maker / hobbyist

Pet project

Getting started developing IoT devices

• Design architecture & select language, development tools/platform

• Select hardware (sensors, actuators, dev board)

• Develop programs to read from sensors & control actuators

• Develop programs to communicate with other devices or services that process / analyze data

MicroPython

• Python 3.x for microcontrollers

• Features: REPL, filesystem, aims to be a compatible subset of Cpython & core libraries

• machine library for hardware / GPIO

• Open Source: MIT license

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

SELECTING HARDWARE

MicroPython Compatible Hardware

• pyboard

• TI CC3200 microcontrollers (e.g. WiPy)

• 16 bit PIC microcontrollers

• Teensy 3.1

• Unix (for x86/x64/ARM/MIPS)

• ESP8266

• ESP32 (experimental)

Which ESP8266 dev board?

• Adafruit Feather HUZZAH ESP8266: https://learn.adafruit.com/adafruit-feather-huzzah-esp8266/overview

• WeMos D1 mini: https://wiki.wemos.cc/products:d1:d1_mini

• NodeMCU: http://nodemcu.com/index_en.html

• Features:• WiFi• 4MB flash• 80MHz processor• 3.3V logic• Up to 11 digital I/O pins, 1 analog I/O pin• Support for (software) I2C, SPI• Feature Huzzah has built in 100mA LiPo

charger

https://learn.adafruit.com/adafruit-feather-huzzah-esp8266/pinouts

Incremental prototyping

• Design the desired interactions

• Work out what components you'll need

• Develop a basic program for each individual component (e.g. read from button , play sound on buzzer, display pattern on LEDs)

• Develop networking / communication

• Use REPL to interactively tweak timings / behaviour

Pet Circuit

Preparing the board

• First install any USB-serial drivers required for your board e.g. CP2104, CH341

• Install Python and esptoolpip install esptool

https://github.com/espressif/esptool

• Erase the flash of the microcontroller if youhave used it before:esptool.py --port /dev/tty.SLAB_USBtoUART erase_flash

Flash the firmware

• Download the latest version (e.g. 1.9.1) of MicroPython from GitHub releases:

– https://github.com/micropython/micropython/releases

• Use esptool to upload the firmware file:• esptool.py --port /dev/tty.SLAB_USBtoUART --baud

460800 write_flash --flash_size=detect 0 ~/Downloads/esp8266-20170612-v1.9.1.bin

Connect to the board

• Connect to REPL via serial (i.e. USB):– Default BAUD rate is 115200

– screen /dev/tty.SLAB_USBtoUART 115200

• Hit control-e to enter paste mode (to paste longer programs)

• You can upload / manage the python program files on the board using ampy:– https://github.com/adafruit/ampyampy --port /dev/tty.SLAB_USBtoUART put demo.py

Change the Wifi config

• Set the default wifi SSID and password on startup by adding the config to main.py

import network

ap=network.WLAN(network.AP_IF)

ap.config(essid="mycustomssid", password="mypassword")

• upload the main.py file

• restart the microcontroller

WebREPL

• You can upload / access the REPL over WiFi• You’ll need to connect via a wired connection to

set it up:import webrepl_setup

• You can enable it on boot or start it:import webreplwebrepl.start()

• Join the device’s adhoc Wifi network: default password is micropythoN– http://micropython.org/webrepl/

Uploading code using the WebREPL

DEVELOPING PROGRAMS

Button on pin 12

Using machine library: read from a pin

from machine import Pin

button = Pin(12, Pin.IN, Pin.PULL_UP)

# Read the button value:

button.value()

Poll button value

Analog sensors

• Only one ADC pin

• Max voltage of 1V – use a voltage divider

import machine

adc = machine.ADC(0)adc.read()

Piezo Buzzer on pin 14

Using the machine library

from machine import Pin, PWM

import time

C5 = 523D5 = 587E5 = 659piezo = PWM(Pin(14, Pin.OUT), freq=440, duty=512)

tune = [E5, D5, C5, D5, E5, E5, E5]

for tone in tune:

piezo.freq(tone)

time.sleep(0.5)

piezo.deinit()

Neopixels

• WS2812B light source

– Chainable, individually addressable RGB LEDs

– Many formfactors (pixel, ring, bar, strip etc)

– Each unit is connected via 3.3V, GND and data pin

– Use external power if working with more than a few LEDs

• See https://learn.adafruit.com/adafruit-neopixel-uberguide/overview

Neopixel ring on pin 2

Loading additional libraries

• Many additional components supported through third party libraries e.g. OLED display supported by SSD1306: https://github.com/adafruit/micropython-adafruit-ssd1306– Download the mpy file from releases

– Upload to board using ampy or WebREPLampy --port /dev/tty.SLAB_USBtoUART put ssd1306.mpy

import ssd1306import machine

i2c = machine.I2C(scl=machine.Pin(5), sda=machine.Pin(4))

oled = ssd1306.SSD1306_I2C(128, 64, i2c)

COMMUNICATION

Basic web server (1/2)

Basic web server (2/2)

MQTT

Other options for developing with ESP8266

• NodeMCU Lua

– http://nodemcu.com/index_en.html

• Arduino IDE

– https://github.com/esp8266/Arduino

• Espruino JS

– https://www.espruino.com/EspruinoESP8266

Why MicroPython?

• Clean, intuitive programs

• Great for teaching

• Interactive REPL ideal for experimentation & rapid prototyping

• Edge computing

Read more

• Anna’s blog:

– http://crufti.com/

• Twitter: @AnnaGerber

• Micropython ESP8266 Quick reference:

– https://docs.micropython.org/en/latest/esp8266/esp8266/quickref.html