### Project 8: LCD1602 Display

**Description**

As we all know, screen is one of the best ways for people to interact
with electronic devices.

**Component Knowledge**

1602 is a line that can display 16 characters. There are two lines,
which use IIC communication protocol.

![image34](../media/066e093f1711ada67d3309ddc9bdc66e.png)

**Control Pins**

| SDA | SDA |
| --- | --- |
| SCL | SCL |


#### Project 8.1 LCD 1602 Display Characters

**Description**

We will use library file i2c_lcd.py and lcd_api.py, which should be
saved in the ESP32 memory.

![image35](../media/b5d74645d450d329aded48064bd599c8.png)

**Operations**

Open“Thonny”，click“This computer”→“D:”→“2. Python
Projects”→“pj8_1_lcd1602”. Select “i2c_lcd.py”, right-click your mouse
to select “\ **Upload to /**\ ”，wait for “i2c_lcd.py” to be uploaded to
ESP32; and then select “lcd_api.py”, right-click your mouse to select
“\ **Upload to /**\ ”，wait for “lcd_api.py” to be uploaded to ESP32.

![Img](../media/img-20250603131246.png)

![image36](../media/img-20250603131916.png)

The saved name are i2c_lcd.py and lcd_api.py

![image37](../media/img-20250603132138.png)

**Test Code**

```python
from time import sleep_ms, ticks_ms
from machine import I2C, Pin
from i2c_lcd import I2cLcd

DEFAULT_I2C_ADDR = 0x27

i2c = I2C(scl=Pin(22), sda=Pin(21), freq=400000)
lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 2, 16)

lcd.move_to(1, 0)
lcd.putstr('Hello')
lcd.move_to(1, 1)
lcd.putstr('keyestudio')

# The following line of code should be tested
# using the REPL:

# 1. To print a string to the LCD:
#    lcd.putstr('Hello world')
# 2. To clear the display:
#lcd.clear()
# 3. To control the cursor position:
# lcd.move_to(2, 1)
# 4. To show the cursor:
# lcd.show_cursor()
# 5. To hide the cursor:
#lcd.hide_cursor()
# 6. To set the cursor to blink:
#lcd.blink_cursor_on()
# 7. To stop the cursor on blinking:
#lcd.blink_cursor_off()
# 8. To hide the currently displayed character:
#lcd.display_off()
# 9. To show the currently hidden character:
#lcd.display_on()
# 10. To turn off the backlight:
#lcd.backlight_off()
# 11. To turn ON the backlight:
#lcd.backlight_on()
# 12. To print a single character:
#lcd.putchar('x')
# 13. To print a custom character:
#happy_face = bytearray([0x00, 0x0A, 0x00, 0x04, 0x00, 0x11, 0x0E, 0x00])
#lcd.custom_char(0, happy_face)
#lcd.putchar(chr(0))
```
**Test Result**

The first line of the LCD1602 shows hello and the second line shows
keyestudio.


#### Project 8.2 Dangerous Gas Alarm

**Description**

When a gas sensor detects a high concentration of dangerous gas, the
buzzer will sound an alarm and the display will show dangerous.

**Component Knowledge**

**MQ2 Smoke Sensor**:

It is a gas leak monitoring device for homes and factories, which is
suitable for liquefied gas, benzene, alkyl, alcohol, hydrogen as well as
smoke detection. Our sensor leads to digital pin D and analog output pin
A, which is connected to D as a digital sensor in this project .

![image38](../media/4550c4935e6c08e595a1e8707b54b551.png)

**Control Pin**

| Gas Sensor | 23 |
| --- | --- |
| \ |   |

**Test Code**

```python
from time import sleep_ms, ticks_ms
from machine import SoftI2C, Pin
from i2c_lcd import I2cLcd

DEFAULT_I2C_ADDR = 0x27

scl_pin = Pin(22, Pin.OUT, pull=Pin.PULL_UP)  # GPIO22 with internal pull-up enabled
sda_pin = Pin(21, Pin.OUT, pull=Pin.PULL_UP)  # GPIO21 with internal pull-up enabled

i2c = SoftI2C(scl=Pin(22), sda=Pin(21), freq=100000)
lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 2, 16)

from machine import Pin
import time
gas = Pin(23, Pin.IN, Pin.PULL_UP)

while True:
    gasVal = gas.value()  # Reads the value of button 1
    print("gas =",gasVal)  #Print it out in the shell
    lcd.move_to(1, 1)
    lcd.putstr('val: {}'.format(gasVal))
    if(gasVal == 1):
        #lcd.clear()
        lcd.move_to(1, 0)
        lcd.putstr('Safety       ')
    else:
        lcd.move_to(1, 0)
        lcd.putstr('dangerous')
    time.sleep(0.1) #delay 0.1s
```
**Test Result**

The screen displays "safety" in normal state. However, when the gas
sensor detects some dangerous gases, such as carbon monoxide, at a
certain concentration, the buzzer will sound an alarm and the screen
displays "dangerous".