Hello,
This is my 1st post and I'll try my best to describe the problem.
I've been doing this little project with Arduino Uno, DHT22 sensor and 20x4 display.
A Co-worker has given me I2c module that they have made with pcf8574 chip on it (It isn't used with Arduino, but for debugging and wrote the code in C for the display). And after weeks of unsuccessful attempts to make it work...i figured that the pins are wired differently, I've found a thread where someone had a similliar problem. 2x20 (ST7066U) lcd not working - Displays - Arduino Forum
Basically the pin wiring on pcf8574 is different than what it's supposed to be. Can the library be adjusted and defined differently?
I'm aware that the module is so cheap i could just order a new one that works out of the box, but if there's a way around this one i would be glad to try and ''fix it''.
The display is working, and the I2c module works if its used with the code it was written for on a different application.
EDIT: I've managed to do solve the problem. I've found the constructor in the code.
hd44780_I2Cexp lcd(addr, chiptype, rs,[rw],en,d4,d5,d6,d7,bl,blpol);
hd44780_I2Cexp lcd(0x27, I2Cexp_PCF8574, 0,1,2,4,5,6,7,3,HIGH); // with rw support
And managed to edit and change so the pinout is correct. The display is working now.