KY040

An Arduino library for KY-040 rotary encoders. The library has debouncing and works in polling mode, with pin change interrupts or normal interrupts. In polling or pin change interrupt mode you can attach more then one rotary encoder to your Arduino Uno/Nano.

PDF-Documentation

Examples how to use the library

License and copyright

Appendix

Background

KY040 is library for KY-040 rotary encoders. There are a lot of libraries existing for KY-040, but I found no library (at least 12/2023) which

works without the need of interrupt enabled pins for the CLK (aka. A) and DT (aka. B)
and has a stable debouncing using a signal state table (without debouncing the KY-040 rotary encoder is a mess)

So I wrote my own library KY040, which was designed to work on an Arduino Uno/Nano or ATmega328 and could work on other Arduino compatible MCUs too.

The KY040 library can:

be used without interrupts in polling mode
be used with pin change interrupts
control more than one rotary encoders in polling or pin change interrupt mode on an Arduino Uno/Nano
use any common pin digital pins for CLK and DT in polling or pin change interrupt mode
be used with normal attachInterrupt interrupts (in this case could have to use Pins 2 and 3 on your Arduino Uno/Nano)
be used with SLEEP_MODE_PWR_SAVE/SLEEP_MODE_PWR_DOWN sleep mode in combination with pin change interrupts
debounce the rotary encoder by filtering out invalid signal sequences

Valid clockwise sequence

        0 1 2 3
    --+   +----   High
CLK   |   |
      +---+       Low
      
    ----+   +--   High
DT      |   |
        +---+     Low

Step	Signal level for CLK/DT
0	Low/High
1	Low/Low
2	High/Low
3	High/High

Valid counter-clockwise sequence

       0 1 2 3
    ----+   +---  High
CLK     |   |
        +---+     Low
        
    --+   +-----  High
DT    |   |
      +---+       Low

Step	Signal level for CLK/DT
0	High/Low
1	Low/Low
2	Low/High
3	High/High

KY-040 Hardware

Pins	Comment
GND	Ground
+	Vcc
SW	Switch button, not covered by this library. You can use digitalRead statements to check SW. Pin is pulled up to Vcc via the 10k pullup resistor R3
DT	aka. B, Pin is pulled up to Vcc via the 10k pullup resistor R2
CLK	aka. A, Pin is pulled up to Vcc via the 10k pullup resistor R1

The three 10k resistors R1,R2 and R3 pulls up the SW, CLK and DT pins up to Vcc.

codingABI/KY040