my Raspberry Pi projects

connecting an HD44780 LCD module

schematic

schematic

Only digital signals are shown.

list of parts

GPIO pins required

software

Library and “Hello, World!” demo in Python by me:

connecting a matrix keypad with up to 10×4 buttons

schematic

preview of schematic

A 4×4-button keypad is used. Only digital signals are shown.

To extend the schematic for keypads with up to 10×4 buttons:

Note: my schematic is much more complex than those commonly used with keypads. However, my schematic allows detecting any number of keys pressed simultaneously. Also, my schematic does not need I/O pins that can be programmatically toggled between input and output.

list of parts

GPIO pins required

software

Library and demo in Python (for a 4×4-button keypad):

(The schematics were drawn with TinyCAD.)