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dbrgn / RPLCD

A Raspberry Pi LCD library for the widely used Hitachi HD44780 controller, written in Python. GPIO (parallel) and I²C modes supported.
https://rplcd.readthedocs.io/en/latest/
MIT License
261 stars 72 forks source link

Writing not possible, just background light control #119

Closed rodentooth closed 4 years ago

rodentooth commented 4 years ago

I use the backpack PCF8574t and a 20x4 blue white display. I have all required prerequisites, the i2c detects the device and the contrast is set to high. Yet, my display shows this on init, clear and any other command:

https://i.stack.imgur.com/YL57y.jpg

Backlight control works

dbrgn commented 4 years ago

Hm, my guess would be that the contrast is set too high?

Do you control it using a pot on the backpack?

rodentooth commented 4 years ago

Hi Daniel

Many thanks for your reply. I tried twiddling around with the contrast, not helping either. only the two full bars like in the image. The contrast is set on the backback, yes

dbrgn commented 4 years ago

Ok, then I don't know unfortunately what causes this, sorry. You might want to check whether there are significant differences between the PCF8574 and the PCF8574t.