Hi Neil,
if you use a Waveshare LCD, there’s a chanche that your display is an RGB type instead of the one used in this tutorial. In this case, I suggest to try their test procedure, as explained in https://www.waveshare.com/wiki/Template:LCD1602_RGB_Module_Guides_for_Pico

The code appears to run correctly but nothing appears on the screen. I can write successfully with the Waveshare RGB1602.py library but nothing else.

At this point it’s really hard for me to help from remote. Is the LCD new? Or you already used it with another controller? I can’t even exclude that the LCD may also be defective and you could ask the vendor to give you help or a new one

I suspect that it has a different chip (as the i2c address is different from that I tested. Would you like to try the following, please:
https://github.com/Bucknalla/micropython-i2c-lcd

I get 0x3E (62 DEC) from scan.

I use below code in Thonny and it doesn’t give any error message so the code works fine.

import machine
from machine import I2C
from lcd_api import LcdApi
from i2c_lcd import I2cLcd
# setup LCD object
I2C_ADDR = 0x3E
I2C_NUM_ROWS = 2
I2C_NUM_COLS = 16
i2c = I2C(0, sda=machine.Pin(0), scl=machine.Pin(1), freq=400000)
lcd = I2cLcd(i2c, I2C_ADDR, I2C_NUM_ROWS, I2C_NUM_COLS)
# creating custom icon
heart = bytearray([0x00,0x0a,0x1f,0x1f,0x0e,0x04,0x00,0x00])
lcd.custom_char(0, heart)
# Main program
lcd.putstr(“Hello from\n”+chr(0)+” peppe80 “+chr(0))

ok. What is the I2C address you get from the LCD?

The Grove I2C 16×2 LCD doesn’t seem to have a screw (potentiometer) to change contrast? Is there I2C function available or only HW capable to change contrast?

Thanks
Bart

Hi Bart. Please, can you try changing the contrast? There should be a screw in the back of your LCD