i2C display + regular display don't work together

[camsysca]

@bperrybap

The OP has provided ZERO information with respect to photos, schematics, PCB layout, or even the library being used for LiquidCrystal_SR even though it has been asked for multiple times.

I stand by my comment, since the whole point is that due to the lack of useful context provided, ANY solution might be THE solution.
Whatever.

[bperrybap]

I agree that having both LCDs use i2c is ideal and the way I'd go, but since we know nothing about his PCB or his environment and how things are connected, we have no idea what is involved in switching the second LCD to be controlled by a PCF8574 instead of a shift register.
It might be no big deal, or it might require a new PCB; we simply don't know given the lack of information provided.

--- bill

[bperrybap]

@gizi

I could remove shift register, and I would have enough pins,

I'm assuming you are aware that i2c is a bus.
i.e. no matter how many slaves you have, it only uses 2 pins.
1, 2, 3, (or more) ... i2c based LCDs would only use 2 i2c pins.

--- bill

[gizi]

We already sloved the Problem with 2 Librarys that work well together.
A regular LCD with shift register + i2C LCD

For a regular LCD with shift register I used

@gizi

#include <LiquidCrystal_SR.h>
LiquidCrystal_SR lcd1(2, 4, 3);

and for the i2C I used a very nice and g8 library

@gizi

#include <hd44780.h>                       // main hd44780 header
#include <hd44780ioClass/hd44780_I2Cexp.h> // i2c expander i/o class header