SerLCD shows block characters

Components & Accessories Displays
1

Dear All,
I am writing to you because I need your help please regarding an issue with a 20x4 SerLCD.
In my project I have connected two SerLCDs with a Feather assigning two different I2C addresses. The problem is that sometimes the second SerLCD shows block characters.
The most of the times it works fine for a couple of hours but randomly shows block characters. Both SerLCDs share the same Ground, Power and I2C line and I have connected the Feather and the LCDs with jumper wires.
Could you please advise me if you have any idea of what the problem could be?
I am looking forward to hearing from you.
Best regards,
George

2

You likely need to disable the i2c pull-up resistors on one of the screens by de-soldering the blob here

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to disconnect those pads

You could also try to use a secondary i2c bus separately if your MCU has one, or swap the second screen to use UART or SPI

3

Try connecting a 10k to 100k resistor between RX and VCC on both screens and see if that gets rid of the blocks.

4

Thank you very much! I will try that.