Use a Minimum of Pins to Manage 16 Button Keyboards

Step 1: IntroductionI recently worked on a way to manage 4x4 touch keyboard matrices connected to Arduino clones. The setpoints are:-Use only 4 1 pins instead of 8 pins on atmega328p

-Add LCD display 4x20 char link through I2C (2 pin)-To control digital and analog outputs.Step 2: what to use:

I purchased a 4x20 character LCD display and an I2C module adapter to connect the display with SDA (A4) and SCL (A5) pins on my Arduino clone.I used the famous and now outdated mm74c922n: 8 to 4-way converter, which is suitable for 4x4 matrix keyboard.I created an Arduino based clone based on

Step 3: schematic diagram and development board:The plate is made of the following materials:-The LCD keyboard is only available for Arduino IDE, not ldmicro (Ladder programming)

-Mm74c922n board: 16 buttons encoded on 16 binary values on 4-bit DCBA. When the button is pressed: the blue LED lights up and a value appears on the DCBA (a is LSB). When the button is released: the blue LED goes out and the value on the DCBA is reset to zero.-Arduino atmega238p clone board.Step 4: use ldmicro with ladder programming:

The code to be entered consists of 4 of the 16 key values, so it is a combination of 16x16x16x16.After drawing the SFC, you must convert it to mineThe ladder diagram is carried out according to the method given in one of the instructables:

https//www.instructables.com/id/Arduino-tomation -..After typing, compile it into xxxx.hex, and then download it using the khazama downloader.LCD display cannot be programmed on ldmicro.

I attached the sketch serrue.id and khazama downloader to ldmicro zip.Step 5: use Arduino ide 1.8. X with mightycore and smlib:I convert SFC to a state machine. Then, I use the Arduino ide with the mightycore and SM libraries.

I display the following messages: error, wait, unlock, status reached, key value on LCD display.I'll give you sketches and SM library. For mightycore, see the following:https//www.instructables.com/id/Arduino-18x-Clone ..

Step 6: conclusion:These are two ways to manage 16 keyboards. It took me several hours to find a good order, but now it can be used normally. You must follow these steps:-1 the key on the rising edge of Da pin is detected

-2 read the value generated on DCBA and compare it with the normal valueUnless it definitely doesn't work.