I2C LCD Library... Help!

Discuss development of drivers for external hardware and components, such as LCD screens, sensors, motor drivers, etc.
Target audience: Users and developers of drivers.
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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Sat Mar 18, 2017 9:28 pm

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.

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dhylands
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Re: I2C LCD Library... Help!

Postby dhylands » Sat Mar 18, 2017 10:09 pm

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.

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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Mon Mar 20, 2017 8:30 am

I soldered all pins from LCD to backpack and now all is ok. :-)
Thanks for troubleshuting.
LED_front1.jpg
LED_front1.jpg (185.53 KiB) Viewed 431 times


>>> 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 :-) ')

haks
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Re: I2C LCD Library... Help!

Postby haks » Thu Apr 06, 2017 10:07 pm

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 :-) ')

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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Sat Apr 08, 2017 7:52 am

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.

Code: Select all

C:\>set AMPY_PORT=COM10
C:\>ampy put lcd_api.py
C:\>ampy put esp8266_i2c_lcd.py esp8266_i2c_lcd.py


Then check if library loaded correctly:

Code: Select all

>>> with open('esp8266_i2c_lcd.py') as f:
            for line in f:
                print(line, end='')

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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Fri Apr 14, 2017 7:27 am

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"?

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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Fri Apr 14, 2017 7:44 am

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.
low_Brightness.jpg
low_Brightness.jpg (106.48 KiB) Viewed 333 times



Than I disconnect 3V3 pin and connect it again to 3V3 pin

>>> lcd.putstr(' Thanks from Ukraine :-) ')
ok_Brightness_wrong_char.jpg
ok_Brightness_wrong_char.jpg (112.79 KiB) Viewed 333 times

"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 . :D

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Roberthh
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Re: I2C LCD Library... Help!

Postby Roberthh » Fri Apr 14, 2017 12:50 pm

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.

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mcauser
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Re: I2C LCD Library... Help!

Postby mcauser » Wed Apr 19, 2017 2:28 am

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.

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raspi3ua
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Re: I2C LCD Library... Help!

Postby raspi3ua » Sat Apr 29, 2017 12:33 pm

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.
I2C_Converter_5V_to_3.3V_TXS0108E .jpg
I2C_Converter_5V_to_3.3V_TXS0108E .jpg (167.76 KiB) Viewed 254 times


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