The first one is the actual Keypad library, you can download it from the link below We have used Arduino Uno, Note that you can also connect the I2C to A4 (SDA) and A5(SCL) if you prefer.
#Arduino libraries for keypad interface on 12c bus how to
Let us see how to connect the keypad to the I2C Module a 4×4 Membrane Matrix Keypad with PCF8574 I2C port expander module Connecting the two together, note that we do not connect the INT pin Connect Power (VCC, GND and I2C lines Connect to Arduino or your preferred microcontroller. all depending on where you buy them from, and how long you are willing to wait for shipping 🙂 They are much more reliable, as well as quite cheap as well. That is to say if we use one of those PCF8574 I2C IO port expander modules. This definitely solves the first of my problems, but we still need 8 pins to control this keypad… or do we? No, we don’t, we need only 2 pins. You can then interface it with your favourite micro-controller to read the key(s) pressed… These are connected together as shown above. Let us look at the circuit Circuit diagram for a 4×4 Matrix KeypadĪs we can see, to build a 4×4 matrix keypad, we will need 16 momentary switches. These can easily be used to make out own, much more reliable keypad. What does this mean ? Most of us makers will inevitably have a piece of proto-board or strip-board lying around, as well as a few momentary push-button switches. These two flaws can however easily be solved, if we use a bit of technology, and are willing to to a bit of simple circuit construction by ourselves. This means they dont last very long.Ģ) A typical 4×4 Matrix keypad will require 8 of your precious IO pins for itself. These keypads do unfortunately have some serious flaws (in my view anyway)ġ) They are usually of extremely low quality ( especially some of the membrane types from China). Using a matrix keypad is a very easy way to add multiple control buttons to a project, be it to enter a password, or to control different devices.
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