I have made a PCB with several things working with I2C, SPI and digital I/O.
I plan to use Pi4J which seems very good.
For normal digital I/O, no problem I can do what I need.
But for I2C and also SPI, I think I will need some code example.
For example I connected an I2C Lcd screen (2*16) through a PCA9517 volatge level translator.
I would like to create a library to drive this display, but really need some info to start.
Here is the schematic of what I did :
So if some are interested, I can also give some explanation and Gerber X data.