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ESP32  ·  How to  ·  MicroPython  ·  Smart home  ·  SolidCircuit HV3

Heating control with MicroPython on the ESP32 - Part 5

Tobias Eydam
 February 17, 2021

What is this part about?

In this part you will learn:

  • How to control a 2-line LCD display

Connect the LCD display to the ESP32

Okay, in addition to the display, we also need a way to make entries. We don't always want to be shown just one value, but rather choose what we want to be shown. I chose a rotary encoder here. This allows you to navigate through the menu. The one I chose even had a switch built in. The display that I use has an I2C adapter board soldered onto it. So we can even save some pins (although we wouldn't have to do that in this project).

Here is my schematic:

Here the circuit described above is set up.
Here again a detailed view. Unfortunately it has become a bit fuzzy
Another detailed view
And all built into one housing
Previous
Next

For the display and the rotary encoder you need other libraries that I do not want to upload for copyright reasons. You can download it here:

Copy them into the directory on your ESP32 / pyboard / lib. Then you can with upip.install ("micropython-eydam-prototyping-lcd-menu") install my module.

Then you can try briefly whether everything worked:

REPL view raw 
>>> import machine
>>> from esp8266_i2c_lcd import I2cLcd
>>> from rotary_irq_esp import RotaryIRQ
>>> i2c = machine.I2C(0, scl=machine.Pin(22), sda=machine.Pin(21))
>>> lcd = I2cLcd(i2c, 39, 2, 16)
>>> lcd.clear()
>>> lcd.putstr("Hello World")   # "Hello World" should be displayed
>>> r = RotaryIRQ(18,19,0,10,False)
>>> r.value() # turn rotary
0
>>> r.value()
16

OK. In order to present a menu on the display, we first have to think about a structure. I came up with the following (I'll do it in English so that it will look exactly like this in the files later. You can do it directly in German if you want. But make sure that, depending on the display, umlauts may not work ). The menu entry is always in the first line, what is in brackets is in the second:

  • Heater
    • Oven (show oven temperature)
    • Tank upper (show temperature of upper tank)
    • Tank lower (show temperature of tank below)
    • State (show the state of the state machine)
  • WiFi
    • SSID (show SSID)
    • IP (show IP)
    • Signal (show signal strength)
  • ESP32
    • CPU temperature (show CPU temperature)
    • RAM usage (show RAM usage)

To illustrate this, let's create the file menu.json (please refer github) and copy it to the ESP32. Then we need a little more code to display the menu as well. Put the file for you menu.py with the following content:

manu.py view raw 
import machine
import ep_lcd_menu
from rotary_irq_esp import RotaryIRQ
from esp8266_i2c_lcd import I2cLcd

def setup(temps, sm):
    i2c = machine.I2C(0, scl=machine.Pin(22), sda=machine.Pin(21))

    lcd = I2cLcd(i2c, 39, 2, 16)
    lcd.clear()

    r = RotaryIRQ(18, 19, 0, 10, False)

    menu = ep_lcd_menu.menu_rot_enc(
        menu_config_file="menu.json", display_type="1602", display=lcd, rotary=r, button_pin=5)

    menu.load()
    menu.render()
    return menu

In the main.py you have to add the following:

main.py view raw 
import ep_logging
import ep_wifi
import ep_config
import heater_http
import onewire
import ds18x20
import machine
import ubinascii
import statemachine
import menu
import gc

wifi = ep_wifi.wifi("./network_config.json", max_time_wait_for_connect=10)
wlan, ssid, bssid = wifi.connect()
ip = wlan.ifconfig()[0]

logger = ep_logging.colored_logger(appname="main")
logger.notice("WiFi connected")

logger_http = ep_logging.colored_logger(appname="http")

ow = onewire.OneWire(machine.Pin(4))
ds = ds18x20.DS18X20(ow)

ht_config = ep_config.config("ht_config.json")
ht_config.load()
thresh = ht_config.get("")

ds_config = ep_config.config("ds_config.json")
ds_config.load()
temps = ds_config.get("")
get_temp = lambda name: temps[name]["value"] if (name in temps) and ("value" in temps[name]) else 0
sm = statemachine.setup(
    get_temp,
    lambda name: thresh.get(name, 0)
)
sm.init()
sm.step_until_stationary()

def read_temps(timer, ds, temps, sm):
    ds.convert_temp()
    for key in temps:
        temps[key]["value"] = ds.read_temp(ubinascii.unhexlify(temps[key]["id"]))
    sm.step()
    gc.collect()

tim_ds = machine.Timer(0)
tim_ds.init(mode=machine.Timer.PERIODIC, period=5000, callback=lambda timer: read_temps(timer, ds, temps, sm))

http_server = heater_http.setup(wlan, logger_http, ds)
http_server.start()

m = menu.setup()

If you restart the ESP32 now, the menu should appear on the display. With the Rotaty Encoder you can navigate through the menu and with a click on the rotary button you can enter the menu item. However, no values are displayed yet. In the menu.json we have defined which functions should be called in order to display something in the second line:

menu.json view raw 
{
    "title": "Oven",
    "second_line": {
        "reading": "print_T_Oven"
    }
}

We need the function print_T_Oven (and all other functions) still register. Adds the following to this:

main.py view raw 
import ep_logging
import ep_wifi
import ep_config
import heater_http
import onewire
import ds18x20
import machine
import ubinascii
import statemachine
import menu
import gc

wifi = ep_wifi.wifi("./network_config.json", max_time_wait_for_connect=10)
wlan, ssid, bssid = wifi.connect()
ip = wlan.ifconfig()[0]

logger = ep_logging.colored_logger(appname="main")
logger.notice("WiFi connected")

logger_http = ep_logging.colored_logger(appname="http")

ow = onewire.OneWire(machine.Pin(4))
ds = ds18x20.DS18X20(ow)

ht_config = ep_config.config("ht_config.json")
ht_config.load()
thresh = ht_config.get("")

ds_config = ep_config.config("ds_config.json")
ds_config.load()
temps = ds_config.get("")
get_temp = lambda name: temps[name]["value"] if (name in temps) and ("value" in temps[name]) else 0
sm = statemachine.setup(
    get_temp,
    lambda name: thresh.get(name, 0)
)
sm.init()
sm.step_until_stationary()

def read_temps(timer, ds, temps, sm):
    ds.convert_temp()
    for key in temps:
        temps[key]["value"] = ds.read_temp(ubinascii.unhexlify(temps[key]["id"]))
    sm.step()
    gc.collect()

tim_ds = machine.Timer(0)
tim_ds.init(mode=machine.Timer.PERIODIC, period=5000, callback=lambda timer: read_temps(timer, ds, temps, sm))

http_server = heater_http.setup(wlan, logger_http, ds)
http_server.start()

m = menu.setup(get_temp, sm)
m.display_funcs["print_ssid"] = lambda: "{}".format(ssid)
m.display_funcs["print_ip"] = lambda: "{}".format(ip)
m.display_funcs["print_rssi"] = lambda: "{} db".format(wlan.status("rssi")) if wlan.isconnected() else "---"

Or.:

menu.py view raw 
import machine
import ep_lcd_menu
from rotary_irq_esp import RotaryIRQ
from esp8266_i2c_lcd import I2cLcd
import esp32
import gc


def setup(temps, sm):
    i2c = machine.I2C(0, scl=machine.Pin(22), sda=machine.Pin(21))

    lcd = I2cLcd(i2c, 39, 2, 16)
    lcd.clear()

    r = RotaryIRQ(18, 19, 0, 10, False)

    menu = ep_lcd_menu.menu_rot_enc(
        menu_config_file="menu.json", display_type="1602", display=lcd, rotary=r, button_pin=5)

    menu.display_funcs = {
        "print_T_Oven": lambda: "{:.2f} C".format(temps("T_Oven")),
        "print_T_TankU": lambda: "{:.2f} C".format(temps("T_TankU")),
        "print_T_TankL": lambda: "{:.2f} C".format(temps("T_TankL")),
        "print_state": lambda: "{}".format(sm.state),
        "print_cpu_temp": lambda: "{:.2f} C".format((esp32.raw_temperature()-32)*5/9),
        "print_ram": lambda: "{:.1f}/{:.1f}kB".format(gc.mem_free()/1024, (gc.mem_alloc()+gc.mem_free())/1024),
    }

    menu.load()
    menu.render()
    return menu

We could do everything in that too main.py write, but I put as much as possible in the menu.py, so that main.py remains as clear as possible.

Our menu is now finished. Feel free to expand it if you want. In the next chapter you will find out how to send the data to an MQTT broker via MQTT.


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