No need for sorry... 
My display worked with original I2C lib.
I think it uses LiquidCrystal_I2C lcd(0x27,20,4); as this was used in the original I2Csample
No idea what pin numbers are used.
At the rear of the display the I2C board is connected.
It has a bridge connector to light the backlight fixed and that is what I use.
So far no need to switch if ON or OFF by software.
So this connector is placed.
When your ideas are placed in the sketch and compiled I get no error.
But after reset the display is empty and the back light is flashing when the LED connector is placed.
It should be so easy...................
I2c sample does not work either.
Paco
