I2C LCD Interface Module

shteii01

Joined Feb 19, 2010
4,644
It looks like the board designer gave you some options,
Technically the designer should do that because you can have multiple devices on I2C bus and they might have the same default/factory address. So the user must be able to change the default address to some other address so that two or more devices on I2C bus do not conflict.
 

GopherT

Joined Nov 23, 2012
8,009
Technically the designer should do that because you can have multiple devices on I2C bus and they might have the same default/factory address. So the user must be able to change the default address to some other address so that two or more devices on I2C bus do not conflict.
I know they should do that, the problem with lots of eBay boards like this is that they often (usually) do not.
 

ErnieM

Joined Apr 24, 2011
8,377
This board shares a genetic heritage with several other boards that all do a similar function. They are not dedicated LCD controllers but rather a generic port expander. Basically they just give you an extra byte of data I/O lines.

So to use these it is very similar to connecting the display directly to a port: you need to send the same data with the same delays, just sending it over the I2C instead of to a port.

The base chip PCF8574 has internal pull ups on the address lines A0 -A2 so it is curious they added external 10k resistors. Just short them to ground at the pads to change the address if you have a conflict. I would leave them as is.
 
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