diagram.json

import time
import json
import network
import ssd1306

from machine import Pin, I2C
from umqtt.simple import MQTTClient
from ucollections import OrderedDict

# Modify wherever the values contain <>
MQTT_BROKER = "broker.hivemq.com"
MQTT_CLIENT_ID = "control-unit-<class>-<number in class>-<name>"
MQTT_TOPIC = "elsys/tcu/<class>/<number in class>/<name>/temperature-sensor/"

# Button pin
BUTTON_PIN = 34

# Display Constants
DISPLAY_SCL_PIN = 21
DISPLAY_SDA_PIN = 22
DISPLAY_WIDTH = 128
DISPLAY_HEIGHT = 64

# Control unit operational variables
control_unit_state = True
number_of_sensors = 2
temperature_values = {}
for i in range(number_of_sensors):
    temperature_values[str(i + 1)] = float("NaN")

# Connect to Wi-Fi
def connect_to_wifi():
    print("Connecting to Wi-Fi", end="")
    sta_if = network.WLAN(network.STA_IF)
    sta_if.active(True)
    sta_if.connect('Wokwi-GUEST', '')
    while not sta_if.isconnected():
        print(".", end="")
        time.sleep(0.1)
    print(" Connected!")

# Connect to MQTT Broker
def connect_to_mqtt_broker():
    connect_to_wifi()
    print("Connecting to MQTT server... ", end="")
    client.connect()
    print("Connected!")
    client.subscribe(MQTT_TOPIC + "#")
    print("Subscribed to {}".format(MQTT_TOPIC + "#"))

# Handle MQTT messages
def on_message(topic, message):
    global temperature_values
    topic = topic.decode("utf-8")
    message = json.loads(message.decode("utf-8"))
    if message["sender"] == "Sensor":
        print("Received from {}: {}".format(topic, str(message)))
        sensor_id = topic.split("/")[-1]
        temperature_values[sensor_id] = message["temp"]
        update_display()

# Update display
def update_display():
    clear_display()
    values = OrderedDict(sorted(temperature_values.items()))
    txt = "{sensor} | {temperature} | {state}"
    for index, (key, value) in enumerate(values.items()):
        display.text(txt.format(sensor=key, temperature=value, state="ON" if control_unit_state else "OFF"), 0, 5 + 15 * index)
    display.show()

# Clear display
def clear_display():
    display.fill(0)
    display.show()

# Publish on/off when button is pressed
def publish_button(pin):
    global control_unit_state
    control_unit_state = not control_unit_state
    update_display()
    for key, value in temperature_values.items():
        topic = MQTT_TOPIC + key
        message = {
            "sender": "Control Unit",
            "state": "ON" if control_unit_state else "OFF"
        }
        client.publish(topic, json.dumps(message))
        print("Published to {}: {}".format(topic, str(message)))

# Init MQTT client
client = MQTTClient(MQTT_CLIENT_ID, MQTT_BROKER)
client.set_callback(on_message)
connect_to_mqtt_broker()

# Init ON/OFF button
Pin(BUTTON_PIN, Pin.IN, Pin.PULL_DOWN).irq(trigger=Pin.IRQ_RISING, handler=publish_button)

# Init OLED Display
i2c = I2C(0, scl=Pin(DISPLAY_SCL_PIN), sda=Pin(DISPLAY_SDA_PIN))
display = ssd1306.SSD1306_I2C(DISPLAY_WIDTH, DISPLAY_HEIGHT, i2c)

# Loop
try:
    update_display()
    while 1:
        client.wait_msg()
finally:
    client.disconnect()


main.py

#MicroPython SSD1306 OLED driver, I2C and SPI interfaces created by Adafruit

import time
import framebuf

# register definitions
SET_CONTRAST        = const(0x81)
SET_ENTIRE_ON       = const(0xa4)
SET_NORM_INV        = const(0xa6)
SET_DISP            = const(0xae)
SET_MEM_ADDR        = const(0x20)
SET_COL_ADDR        = const(0x21)
SET_PAGE_ADDR       = const(0x22)
SET_DISP_START_LINE = const(0x40)
SET_SEG_REMAP       = const(0xa0)
SET_MUX_RATIO       = const(0xa8)
SET_COM_OUT_DIR     = const(0xc0)
SET_DISP_OFFSET     = const(0xd3)
SET_COM_PIN_CFG     = const(0xda)
SET_DISP_CLK_DIV    = const(0xd5)
SET_PRECHARGE       = const(0xd9)
SET_VCOM_DESEL      = const(0xdb)
SET_CHARGE_PUMP     = const(0x8d)


class SSD1306:
    def __init__(self, width, height, external_vcc):
        self.width = width
        self.height = height
        self.external_vcc = external_vcc
        self.pages = self.height // 8
        # Note the subclass must initialize self.framebuf to a framebuffer.
        # This is necessary because the underlying data buffer is different
        # between I2C and SPI implementations (I2C needs an extra byte).
        self.poweron()
        self.init_display()

    def init_display(self):
        for cmd in (
            SET_DISP | 0x00, # off
            # address setting
            SET_MEM_ADDR, 0x00, # horizontal
            # resolution and layout
            SET_DISP_START_LINE | 0x00,
            SET_SEG_REMAP | 0x01, # column addr 127 mapped to SEG0
            SET_MUX_RATIO, self.height - 1,
            SET_COM_OUT_DIR | 0x08, # scan from COM[N] to COM0
            SET_DISP_OFFSET, 0x00,
            SET_COM_PIN_CFG, 0x02 if self.height == 32 else 0x12,
            # timing and driving scheme
            SET_DISP_CLK_DIV, 0x80,
            SET_PRECHARGE, 0x22 if self.external_vcc else 0xf1,
            SET_VCOM_DESEL, 0x30, # 0.83*Vcc
            # display
            SET_CONTRAST, 0xff, # maximum
            SET_ENTIRE_ON, # output follows RAM contents
            SET_NORM_INV, # not inverted
            # charge pump
            SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01): # on
            self.write_cmd(cmd)
        self.fill(0)
        self.show()

    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)

    def contrast(self, contrast):
        self.write_cmd(SET_CONTRAST)
        self.write_cmd(contrast)

    def invert(self, invert):
        self.write_cmd(SET_NORM_INV | (invert & 1))

    def show(self):
        x0 = 0
        x1 = self.width - 1
        if self.width == 64:
            # displays with width of 64 pixels are shifted by 32
            x0 += 32
            x1 += 32
        self.write_cmd(SET_COL_ADDR)
        self.write_cmd(x0)
        self.write_cmd(x1)
        self.write_cmd(SET_PAGE_ADDR)
        self.write_cmd(0)
        self.write_cmd(self.pages - 1)
        self.write_framebuf()

    def fill(self, col):
        self.framebuf.fill(col)

    def pixel(self, x, y, col):
        self.framebuf.pixel(x, y, col)

    def scroll(self, dx, dy):
        self.framebuf.scroll(dx, dy)

    def text(self, string, x, y, col=1):
        self.framebuf.text(string, x, y, col)


class SSD1306_I2C(SSD1306):
    def __init__(self, width, height, i2c, addr=0x3c, external_vcc=False):
        self.i2c = i2c
        self.addr = addr
        self.temp = bytearray(2)
        # Add an extra byte to the data buffer to hold an I2C data/command byte
        # to use hardware-compatible I2C transactions.  A memoryview of the
        # buffer is used to mask this byte from the framebuffer operations
        # (without a major memory hit as memoryview doesn't copy to a separate
        # buffer).
        self.buffer = bytearray(((height // 8) * width) + 1)
        self.buffer[0] = 0x40  # Set first byte of data buffer to Co=0, D/C=1
        self.framebuf = framebuf.FrameBuffer1(memoryview(self.buffer)[1:], width, height)
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.temp[0] = 0x80 # Co=1, D/C#=0
        self.temp[1] = cmd
        self.i2c.writeto(self.addr, self.temp)

    def write_framebuf(self):
        # Blast out the frame buffer using a single I2C transaction to support
        # hardware I2C interfaces.
        self.i2c.writeto(self.addr, self.buffer)

    def poweron(self):
        pass


class SSD1306_SPI(SSD1306):
    def __init__(self, width, height, spi, dc, res, cs, external_vcc=False):
        self.rate = 10 * 1024 * 1024
        dc.init(dc.OUT, value=0)
        res.init(res.OUT, value=0)
        cs.init(cs.OUT, value=1)
        self.spi = spi
        self.dc = dc
        self.res = res
        self.cs = cs
        self.buffer = bytearray((height // 8) * width)
        self.framebuf = framebuf.FrameBuffer1(self.buffer, width, height)
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs.high()
        self.dc.low()
        self.cs.low()
        self.spi.write(bytearray([cmd]))
        self.cs.high()

    def write_framebuf(self):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs.high()
        self.dc.high()
        self.cs.low()
        self.spi.write(self.buffer)
        self.cs.high()

    def poweron(self):
        self.res.high()
        time.sleep_ms(1)
        self.res.low()
        time.sleep_ms(10)
        self.res.high()
