This howto assumes Ubuntu 18.04+ is used on the computer and several tools have been installed:
sudo apt install picocom make python3-pip sudo pip3 install esptool adafruit-ampy
Clone the Git repository and run makefiles:
git clone https://git.k-space.ee/k-space/micropython-skeleton cd micropython-skeleton make
In order to access the serial port you likely need to add yourself to the
dialout group after which you need to
log out from your desktop session and log in again
sudo gpasswd -a $USER dialout
If you're using one of the computers prepared for the workshop all the steps above have been performed already for you
To open serial to the microcontroller:
Note that serial connection is used by both so you can't upload scripts while serial console is open in another window
First let's some LED-s blinking. Press Ctrl-E for paste mode, otherwise spaces get mangled. Press Ctrl-Shift-V for pasting. Press Ctrl-D to exit paste mode and evaluate the code.
from time import sleep from machine import Pin # RGB LED is connected to programmable pins 12, 13, 15 led_red = Pin(12, Pin.OUT) led_green = Pin(13, Pin.OUT) led_blue = Pin(15, Pin.OUT) # The values are inverted because 3.3v is common pin led_red.value(1) led_green.value(1) led_blue.value(1) for j in range(0, 5): led_red.value(0) sleep(1) led_red.value(1) led_green.value(0) sleep(1) led_green.value(1) led_blue.value(0) sleep(1) led_blue.value(1)
- Modify the code so yellow, cyan, magenda and white would be included.
On the board there is button labelled "Boot", this is hooked up to pin 2. By default there is a resistor which pulls the voltage on the pin to 3.3v, but when button is pressed the pin is shorted to ground so the voltage goes to 0v. Most modern solutions use interrupts to detect voltage change on the pin:
from machine import Pin from time import sleep Pin(12, Pin.OUT).value(1) Pin(13, Pin.OUT).value(1) led_blue = Pin(15, Pin.OUT) button = Pin(0) turned_off = False def callback(p): global turned_off turned_off = not turned_off led_blue.value(turned_off) # Execute function 'callback' when voltage goes from 3.3v to 0v on pin 0 button.irq(trigger=Pin.IRQ_FALLING, handler=callback)
- Modify the code so pressing button shuffles between off, red, green, blue, yellow, cyan, magenta and white
Driving OLED screens
Let's get some pixels on the screen! There's 128x64 pixels monochrome OLED screen connected via I2C bus on the pins 4 and 5.
from machine import Pin, SoftI2C from ssd1306 import SSD1306_I2C i2c = SoftI2C(Pin(4),Pin(5), freq=400000) # Bitbanged I2C bus oled = SSD1306_I2C(128, 64, i2c) oled.invert(0) # White text on black background oled.contrast(255) # Maximum contrast oled.fill(0) name = "Hello MicroPython!" oled.text(" %s" % name, 10, 10) oled.show()
- What IP address was assigned to the board by the wireless network?
Hint: Check out
- Show button press counter on the screen
- Show on the screen which color is the RGB LED shining
Most boards to do not have battery backed time keep track of the time. Once you have the microcontroller connected to the Internet you can query time from one of the NTP servers.
The Internet connectivity is established using
boot.py script that is
already included in this repo. It by default connects to
Temperature & humidity
Next let's hook up DHT11 sensor to the board and measure the temperature.
- Sensor's Vcc is connected to 3.3v on the board
- Ground pins (GND) are connected
- Sensor's data pin is connected to board pin 4
Some code to get you going:
from time import sleep from machine import Pin from dht import DHT11 d = DHT11(Pin(4)) try: d.measure() except OSError: print("Sensor not connected") else: print("Temperature %sC" % d.temperature()) print("Humidity %s%%" % d.humidity()) finally: sleep(1)
- Get temperature and humidity displayed on the screen
Distance with sonar
In this case HC-SR04 is hooked up:
- Trigger is connected to pin 12
- Echo is connected to pin 14
- GND pins are connected
- Sonar's Vcc is connected to 3.3V on the board
This is exactly the case with the sumorobots. Feel free to try it out!
Code to measure distance:
from time import sleep_us, sleep_ms from machine import Pin, time_pulse_us trigger = Pin(12, Pin.OUT) echo = Pin(14, Pin.IN) def measure(): trigger.value(0) sleep_us(5) trigger.value(1) sleep_us(10) trigger.value(0) duration = time_pulse_us(echo, 1, 29000) distance = (duration / 2.0) / 29 return distance while True: print("Distance is: %s cm" % measure()) sleep_ms(200)
- Get distance shown on OLED display
- How were the constants for converting
ESP32 microcontroller with MicroPython is a really cheap way to get started with the IoT stuff. See more detailed information here.
Other interesting projects with ESP8266 and ESP32 microcontrollers:
Come and visit k-space.ee on Wednesdays 18:00 for more of MicroPython