Enter MicroPython Python meets the metal Alejandro Guirao @lekum github.com/lekum 

What is MicroPython MicroPython is a lean and efficient implementation of the Python 3 programming language that includes a small subset of the Python standard library and is optimised to run on microcontrollers and in constrained environments Just 256k of code space and 16k of RAM! 

Features of Micropython ● Python compiler + runtime that runs on bare-metal ● REPL + ability to run and import scripts from the filesystem ● Arbitrary precision integers, closures, list comprehension, generators, exception handling... 

Supported boards Pyboard ESP8266 WiPy BBC Micro:bit https://github.com/micropython/micropython/wiki/Boards-Summary 

ESP8266 

The ESP8266 The ESP8266 is a low-cost Wi-Fi chip with full TCP/IP stack and MCU (Micro Controller Unit) capability produced by Espressif Systems Microcontroller ESP-8266EX Operating Voltage 3.3V Digital I/O Pins 11 Analog Input Pins 1(Max input: 3.2V) Clock Speed 80MHz/160MHz Flash 16M bytes Length 34.2mm Width 25.6mm Weight 2.5g 

MicroPython installation ● Download a firmware for the ESP8266 (http://micropython.org/download#esp8266) ● Install esptool.py ○ pip install esptool ● Connect the board and take note of the port (e.g. /dev/ttyUSB0) that shows up in the output of dmesg command ● Erase the flash memory of the board: ○ esptool.py --port /dev/ttyUSB0 erase_flash ● Flash with the firmware: ○ esptool.py --port /dev/ttyUSB0 write_flash -fm dio -fs 32m 0 esp8266-20170108-v1.8.7.bin 

Using the REPL Install picocom and connect to the serial interface: picocom -b 115200 /dev/ttyUSB0 You should see the MicroPython REPL: MicroPython v1.8.7-7-gb5a1a20a3 on 2017-01-09; ESP module with ESP8266 Type "help()" for more information. >>> 

Blinking the built-in LED >>> from machine import Pin >>> led = Pin(2, Pin.OUT) >>> for i in range(10): ... led.high() ... led.low() ... ... >>> 

Code upload and execution ● We will use adafruit-ampy ● Installation: ○ pip install adafruit-ampy ● Set up the port connection: ○ export AMPY_PORT=/dev/ttyUSB0 ● Test it: ○ ampy ls 

Workflow ● Edit your script main.py ● Perform one-shot run and get console output: ○ ampy run main.py ● Upload the file to the board: ○ ampy put main.py ● Restart the board! 

Project A: Slack button 

Schematics from machine import Pin button = Pin(0) if button.value(): print("The button is not pressed.") else: print("The button is pressed.") 

Connect to a WiFi import network def wifi_connect(ssid, pwd): """ Connect to a wifi 'ssid' with password 'pwd' """ sta_if = network.WLAN(network.STA_IF) ap_if = network.WLAN(network.AP_IF) if ap_if.active(): ap_if.active(False) if not sta_if.isconnected(): print('connecting to network...') sta_if.active(True) sta_if.connect(ssid, pwd) while not sta_if.isconnected(): pass return 'IP address: %s' % sta_if.ifconfig()[0] 

Post to Slack import urequests def to_slack(slack_hook_url, slack_icon_url, slack_message, slack_username): """ Send the 'slack_message' using an incoming webhook """ data = { "link_names": 1, "icon_url": slack_icon_url, "username": slack_username, "text": slack_message } res = urequests.post(slack_hook_url, json=data) return res.status_code == 200 

Main loop (I) import time from machine import Pin if __name__ == "__main__": [...] led_pin = 0 # D3 button_pin = 12 #D6 wifi_connect(SSID, pwd) led = Pin(led_pin, Pin.OUT) button = Pin(button_pin, Pin.IN, Pin.PULL_UP) 

Main loop (II) while True: # Button pressed if not button.value(): print("The button has been pressed") ok = to_slack(slack_hook_url, slack_icon_url, slack_message, slack_username) # If succeed, light the LED during 1s if ok: print("Succeeded posting to Slack") led.high() time.sleep(1) else: print("Failed trying to post to Slack") led.low() time.sleep_ms(10) 

Project B: Temperature and humidity probe 

Main loop from machine import unique_id from ubinascii import hexlify from sht30 import SHT30 from umqtt.simple import MQTTClient [...] mqtt_server = "" mqtt_client_id = "micropython-{}".format(hexlify(unique_id()).decode()) print("mqtt_client_id:", mqtt_client_id) wifi_connect(SSID, pwd) client = MQTTClient(mqtt_client_id, mqtt_server) client.connect() sensor = SHT30() while True: time.sleep(1) temperature, humidity = sensor.measure() client.publish("{}/temperature".format(mqtt_client_id).encode(), "{:.2f}".format(float(str(temperature))).encode()) client.publish("{}/humidity".format(mqtt_client_id).encode(), "{:.2f}".format(float(str(humidity))).encode()) 

Notes ● Get the driver dht.py from https://github.com/rsc1975/micropython-sht30 ● Upload it to the board: ○ ampy put sht30.py ● Send the metrics to any MQTT broker ○ iot.eclipse.org ● Search for these topics: ○ /temperature ○ /humidity 

Visualization https://github.com/lekum/node-red-with-dashboards 

Visualization Android MQTT Dash app 

Further resources http://micropython-on-wemos-d1-mini.readthedocs.io/en/latest/ https://docs.micropython.org/en/latest/esp8266/ https://learn.adafruit.com/search?q=micropython& https://github.com/lekum/esp8266sketches 

BBC Micro:bit 

The BBC Micro:bit It is an ARM-based embedded system designed by the BBC for use in computer education in the UK. ● Size: approx. 5cm x 4cm ● Weight: 8g ● Processor: 32-bit ARM Cortex M0 CPU ● Bluetooth Low Energy ● Digital Compass ● Accelerometer ● Micro-USB controller ● 5x5 LED matrix with 25 red LEDs ● 2 programmable buttons ● Powered by 2x AAA batteries 

Using the REPL Install picocom and connect to the serial interface: picocom -b 115200 /dev/ttyACM0 You should see the MicroPython REPL: MicroPython v1.7-9-gbe020eb on 2016-04-18; micro:bit with nRF51822 Type "help()" for more information. >>> 

Code upload and workflow ● We will use uFlash ● Installation: ○ pip install uflash ● Upload a script ○ uflash main.py ● Auto-upload when changes ○ uflash --watch main.py 

LED “Hello, World!” from microbit import display display.scroll("Hello, World!") 

Built-in images from microbit import Image, display display.show(Image.HAPPY) HEART_SMALL HAPPY SMILE SAD CONFUSED ANGRY ASLEEP SURPRISED SILLY FABULOUS MEH YES NO TRIANGLE TRIANGLE_LEFT CHESSBOARD DIAMOND DIAMOND_SMALL SQUARE SQUARE_SMALL RABBIT COW MUSIC_CROTCHET MUSIC_QUAVER MUSIC_QUAVERS PITCHFORK XMAS PACMAN TARGET TSHIRT ROLLERSKATE DUCK HOUSE TORTOISE BUTTERFLY STICKFIGURE GHOST SWORD GIRAFFE SKULL UMBRELLA SNAKE... 

Pinout 

GPIO from microbit import * while True: pin0.write_digital(1) sleep(20) pin0.write_digital(0) sleep(480) print(pin0.read_analog()) sleep(480) 

Music import music music.play(music.NYAN) music.play([‘c4’, ‘f#’, ‘g’]) DADADADUM ENTERTAINER PRELUDE ODE NYAN RINGTONE FUNK BLUES BIRTHDAY WEDDING FUNERAL PUNCHLINE PYTHON BADDY CHASE BA_DING WAWAWAWAA JUMP_UP JUMP_DOWN POWER_UP POWER_DOWN... 

Project C: Remote compass 

Compass import radio from microbit import display, Image, compass, button_a, button_b, sleep def menu_mode(): """ Principal menu mode """ while True: display.show(Image.HAPPY) radio.send("ready") if button_a.is_pressed(): send_direction() if __name__ == "__main__": radio.on() compass.calibrate() menu_mode() 

Compass (II) def send_direction(): """ Send the direction which the probe is pointing to: direction_N, direction_NE, direction_E... """ display.show(Image.ARROW_N) while True: sleep(100) if button_b.is_pressed(): break # Back to the menu mode heading = compass.heading() if (heading > 337) or (heading <= 22): needle = "N" elif 22 < heading <= 67: needle = "NE" elif 67 < heading <= 112: needle = "E" [...] radio.send("dir_{}".format(needle)) 

Station import radio from microbit import display, Image def decode_direction(dirstring): """ Decode the dir_X and show the arrow """ needle = dirstring.split("dir_")[1] img = getattr(Image, "ARROW_{}".format(needle)) display.show(img) if __name__ == "__main__": radio.on() while True: incoming = radio.receive() if incoming is None: continue elif incoming.startswith("dir_"): decode_direction(incoming) elif incoming == "ready": display.show(Image.HAPPY) 

Further resources https://microbit-micropython.readthedocs.io/en/latest/ http://microbit.org/ideas/ https://github.com/lekum/microbit-sketches/tree/master/micropython/remote_ compass 

Happy hacking! Alejandro Guirao @lekum lekum.org github.com/lekum