Palliser:
I need to interface a 4x4 keypad and a lcd as input and output consoles with the same Arduino uno. I have done each interface but separately. Knowing that the lcd occupies 6 digital pins and the keypad occupies 8 digital pins, there is no capacity in the board to connect them together unless it is done a multiplexing. Right? So, I was thinking to use something like a 4052 (CMOS 4 channel multiplexer) for the sampling and share 4 pins between them and one more pin for the switching. To use the I2C bus also crossed to my mind but seems that it is more elaborated. some recommendations? Thank you!
The I2C buss is simple and there are a ton of lcd library's with support for i2c GPIO's (pick a chip based upon the library). There are plenty of I2C GPIO chips that can handle all the keypad work and let you just poll or attach an interrupt to process the button press (never seen an arduino lib for these but it's pretty trivial to read a register on int or by polling).