MicroPython Forum (Archive)

One of comments from Aliexpress:
"3f address. there is written about it. put the address 0х3f i2c module and start-everything works. https://ae01.alicdn.com/kf/UT8QpQBXNNaXXagOFbXQ.jpg"

So adress 63 is OK.


"The part number of the 0x3F chip will be PCF8574. i.e.0x38-0x3F
The part number of the 0x27 chip will be PCF8574A i.e. 0x20-0x27"
http://forum.arduino.cc/index.php?topic=369998.60


picture: https://cdn.instructables.com/FVV/YTFX/ ... .LARGE.jpg
0x3F - my code.
PCF8574AT - my backpack.

SDA and SCL both need pullup resistors. Some boards have them and some don't. I'd try adding 10K ohm pullups between 3.3v and SDA and also between 3.3v and SCL.

I soldered all pins from LCD to backpack and now all is ok.
Thanks for troubleshuting. >>> from esp8266_i2c_lcd import I2cLcd
>>> from machine import Pin, I2C
>>> i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
>>> i2c.scan()
[63]
>>> lcd = I2cLcd(i2c, 63, 2, 16)
>>> lcd.clear()
>>> lcd.putstr(' Thanks from Ukraine ')

Help: <ImportError: no module named 'esp8266_i2c_lcd'> trying to load the same code:

from esp8266_i2c_lcd import I2cLcd
from machine import Pin, I2C
i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
i2c.scan()
lcd = I2cLcd(i2c, 63, 2, 16)
lcd.clear()
lcd.putstr(' Thanks from Ukraine ')

haks wrote:Help: <ImportError: no module named 'esp8266_i2c_lcd'> trying to load the same code:

from esp8266_i2c_lcd import I2cLcd

There is no 'esp8266_i2c_lcd' library installed by default. You need to load 'esp8266_i2c_lcd' and 'lcd_api.py' on your NodeMCU. I use "ampy" util to load files to Node MPU. Then check if library loaded correctly:

Question: Can we tune "Brightness" and "Contrast" using I2C LCD Library?

I ask this question because of next problem...
When I use wrong connection and power LCD Backpack (5V) from NodeMCU VU pin (5V) - all is ok with "Brightness" and "Contrast". See my picture above. But such connection may faulted I2C pin on NodeMCU (not 5V tolerant).

When I power LCD Backpack (5V) from NodeMCU 3V3 pin (3.3V) - LCD is working BUT "Brightness" and "Contrast" too low. I set potentiometer on Bacpack to max position. I can lcd.putstr('hi") but it very hard readable.

So is it any way to tune "Brightness" and "Contrast"?

Test.
Power LCD Backpack (5V) from NodeMCU 3V3 pin (3.3V).
>>> i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
>>> lcd = I2cLcd(i2c, 63, 2, 16)
>>> lcd.putstr(' Thanks from Ukraine ')
"Brightness" and "Contrast" too low.
Than I disconnect 3V3 pin and connect it again to 3V3 pin

>>> lcd.putstr(' Thanks from Ukraine ') "Brightness" and "Contrast" is ok but Char is wrong.

When I reinitialize LCD+Backpack
>>> i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000)
>>> lcd = I2cLcd(i2c, 63, 2, 16)
Char is good but "Brightness" and "Contrast" is too low again .

The LCD requires 5V for proper brightness & contrast. You could try to run the LCD at 5V, and the NodeMCU at 3.3V with the pull-up resistors connected to 3.3 V. Or use a level converter for SDA & SCL, with pull-up resistors at both sides.

There are some 16x2 LCDs which are designed for 3V, but they are hard to find and often 5-10x the price.
Most require 5V for reasonable contrast. Don't forget to adjust the potentiometer on the back.

Yellow/green LCDs are more readable in daylight without the backlight on, compared to blue/white.

Receive TXS0108E "I2C Logic Level Converter Bi-Directional Module 5V to 3.3V".
Connect LCD (5V) to NodeMCU (3.3V) through TXS0108E.
Now all is Ok.