How can your hardware be working if your software fails on it and yet you claim your software is working under simulation!!! Does not computer sir.

Of course simulation is just that....a simulation. Real hardware is always different.

A common mistake people make when trying to make hardware work for the first time is to throw a whole complex program at it and expect it to work right off.

Instead you need to work in very small child steps. Startout with the very very simplest program you can make. A common simple first step is to wake up out of reset and blink an LED!! Even I still do this with new hardware even though I have previously made dozens of microcontroller systems.

Another common mistake made is to try to get along doing embedded work without an oscilloscope. If you don't have one....then get one and learn how to use it. This will enable you to SEE what is working and not working with your hardware AND software.

Much can be learned about the operation of your software by having it toggle a spare output port pin on and off at different points in your program.

It takes hardware work to get software running on new hardware. All the simulation shows you is how key parts of the logic in your program work. Simulation provides no detail about critical timing issues.....some of which could include:
A) Do I have the E pulse to the LCD wide enough?
B) Is the SCL clock on the I2C bus the correct speed?
C) Is there ringing on the interrupt line which causes that extra interrupt every time I activate the relay?

etc etc

And ALL of these require the oscilloscope to make measurements.

Michael Karas