1602 LCD and I2C backpack with pycom

[tttadam]

Hello there,

Any one of you have experience with old fashion 1602 lcd?
I have an LMB162ABC LCD display with PCF8574 i2c backpack.
Can you recommend a micropython library which is works? :)
I scrolled throw the net, and I found and tested a few, but I run in to various errors.

[VerlaHiltz]

This post is deleted!

[robert-hh]

@Lucas_Vieira I'm missing the print statements form the script. So your test script is not executed at all.

[robert-hh]

@Lucas_Vieira Do you see the other print statements?

[Lucas_Vieira]

@robert-hh
No error, but nothing appears on the display. i'm making a mistake in hardware. even so, thank you man for helping me in this case, i'll try be better!

[robert-hh]

@Lucas_Vieira Stay with the initial set of SCL and SDA, and set

DEFAULT_I2C_ADDR = 63

It is a PCF8574A, not PCF8574.

[Lucas_Vieira]

@robert-hh

[robert-hh]

@Lucas_Vieira with the LCD connected, try the following commands on the REPL command line:

from machine import I2C
i2c=I2C()
i2c.scan()

It should return
[39]
if it returns a different number, you have to change the I2C address in the script. It it returns an empty list, try to swap sda and scl.

[robert-hh]

@Lucas_Vieira Reboot via the reset button to ensure, that main.py is executed. Did you also upload lcd_api.py?

[Lucas_Vieira]

@robert-hh
Thank you for helping me to resolve this error import, but nothing is working in LCD.

LCD is just on.

[robert-hh]

@Lucas_Vieira You are trying the wrong module, since you have a display with i2c backpack. Please copy the files esp8266_i2c_lcd.py and lcd_api.py to you device. Then you can test it with the following code. which is more or less the content of the file esp8266_i2c_lcd_test.py. Do not get confused about the esp8266 prefix. For this application, both board behave similar. Connect the I2C with:

LoPy4      LCD
-------------------------
GND         GND
Vin         Vcc    (assuming you need 5V for the display)
P9          sda
P10         scl

"""Implements a HD44780 character LCD connected via PCF8574 on I2C.
   This was tested with: https://www.wemos.cc/product/d1-mini.html"""

from time import sleep_ms, ticks_ms
from machine import I2C, Pin
from esp8266_i2c_lcd import I2cLcd

# The PCF8574 has a jumper selectable address: 0x20 - 0x27
DEFAULT_I2C_ADDR = 0x27

def test_main():
    """Test function for verifying basic functionality."""
    print("Running test_main")
    i2c = I2C()
    lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 2, 16)
    lcd.putstr("It Works!\nSecond Line")
    sleep_ms(3000)
    lcd.clear()
    count = 0
    while True:
        lcd.move_to(0, 0)
        lcd.putstr("%7d" % (ticks_ms() // 1000))
        sleep_ms(1000)
        count += 1
        if count % 10 == 3:
            print("Turning backlight off")
            lcd.backlight_off()
        if count % 10 == 4:
            print("Turning backlight on")
            lcd.backlight_on()
        if count % 10 == 5:
            print("Turning display off")
            lcd.display_off()
        if count % 10 == 6:
            print("Turning display on")
            lcd.display_on()
        if count % 10 == 7:
            print("Turning display & backlight off")
            lcd.backlight_off()
            lcd.display_off()
        if count % 10 == 8:
            print("Turning display & backlight on")
            lcd.backlight_on()
            lcd.display_on()

#if __name__ == "__main__":
test_main()

[Lucas_Vieira]

@robert-hh

[robert-hh]

@Lucas_Vieira I do not know which environment you are using, but I just copy the files to the device, e.g. mylib.py and write:
import mylib
Preferring the basic style, I do not use any of the IDEs for Atom or VSC.

[Lucas_Vieira]

@robert-hh How can i import a library? It's showing an import error

[robert-hh]

@Lucas_Vieira There are a variety of drivers here:https://github.com/dhylands/python_lcd.git
The one for esp8266_i2c works. The only thing to adapt is the I2C constructor in the test program in line 14, where you have to write:
i22=I2C()
if you connect the I2C to the default pins P9 (sda) and P10 (scl). And the I2C address may have to be changed.
And one hint: The LCD's typically run at 5V. Driving the, at 3.3 V typically results in the LCD not showing anything.

[Lucas_Vieira]

Can you help me with this library? i'm beginner with pycom. i'm using a lopy4. how can i add this library in my code? Thank you very much for your help!!

[tttadam]

I found a library. Work as intended.