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Contents

1. brief introduction
2. how to use
3. Code refrence manual
4. Defines

1. Welcome to the PS2Keyboard wiki! Breef Introduction

PS2Keyboard is a simple library used to read a PS2Keyboard using the PS/2 protocol. Many modern PS2Keyboards still support the PS/2 protocol! You can use it through usb by connecting D+ (the CLOCK pin) to an interrupt pin and D- (the DATA pin) to any digital input pin. (you also have to supply the PS2Keyboard ofcourse)

This library is far from finished and may still contain some bugs. It only supports FR and USkeyboards for now but feel free to contribute.

I decided to make this library since there aren't any good while still simple libraries out there that are currently maintained.

2. How to use

In order to explain, let's start with an example:

#include <PS2Keyboard.h>

PS2Keyboard keyboard;

void setup() {
  Serial.begin(9600);
  keyboard.begin(3, 4);
}

void loop() {
  if(keyboard.has_data()) {
    key_event key = keyboard.read_data();
    
    Serial.println(key.scancode);
  }
}

This example prints out any scancode we receive form the keyboard.

Let's break it down:

• First, we have PS2Keyboard keyboard;, this creates a keyboard with the name keyboard note that you can only have one keyboard. This is the main way we interract with the keyboard by calling methods (EG: keyboard.<method_name>)
• Then in our setup, we have this line keyboard.begin(3, 4); this initializes the keyboard. This method takes 2 integers, they are used to set which pins we connected the keyboard to. We have our CLOCK (D+) connected to pin 3, please make sure that your clock pin is connected to an interrupt pin
• Next, we have this keyboard.has_data(). This method returns true if we have received valid data from the keyboard. You can use this to know when you should start reading the keyboard (so you don't waste time reading the keyboard when there is no data).
• Fourth, we have this piece of code key_event key = keyboard.read_data(); this reads the data form the buffer. When the keyboard receives data, it gets added to the buffer so we can read it at a later moment. When you call this reading function that data gets removed from the buffer so the next time you read, it outputs the next data. This function also returns a custom data structure this is a collection of variables which can be accessed like so:
  • key.scancode(int) this is the unique code of the key that is pressed (note that normal and extended key codes can overlap)
  • key.is_extended(bool) this is true for special key like up_arrowor delete since their codes may overlap with normal scancodes
  • key.is_pressed(bool) this is true when the key is pressed. A keyboard sends 2 different events. When a key is pressed and when it's released so we can use this variable to differenciate those events
• Lastly but surely, we have Serial.println(key.scancode); This just prints the scancode of the key_press we received to the serial monitor

3. Code refrence

begin()

void PS2Keyboard::begin(int clock_pin, int data_pin);

• Description: Initializes the keyboard with clock_pin and data_pin.
• Arguments:
  1. int clock_pin the pin to which your clock (D+ of the usb) is connected to. This must be an interrupt
  2. int data_pin the pin to which your data (D- of the usb) is connected to.
• Returns: void

has_data()

bool PS2Keyboard::has_data(void);

• Description: Returns true when there is valid data in the internal buffer ready to be read.
• Arguments: none
• Returns: boolean Whenever there is any data to be read.

read_data()

key_event PS2Keyboard::read_data(void);

• Description: Read the oldest data from the internal buffer and remove it from the buffer
• Arguments: none
• Returns: key_event custom data struct

struct key_event {
  int scancode; //the unique code for this key
  int is_extended; //true for special keys like _up_arrow_ or _delete_ because their scancodes may overlap with the normal keys
  int is_pressed; //Whenever the key is pressed (true) or released (false)
};

key_to_char_azerty()

char PS2Keyboard::key_to_char_azerty(key_event data, bool shift);

• Description: Converts key data into a charracter according to the azerty (FR) layout
• Arguments:
  1. key_event data the key data of the key you have read.
  2. shift whenever shift is currently pressed so we can change the output char
• Returns: char the key in char form

key_to_char_querty()

char PS2Keyboard::key_to_char_querty(key_event data, bool shift);

• Description: Converts key data into a charracter according to the querty (US) layout
• Arguments:
  1. key_event data the key data of the key you have read.
  2. shift whenever shift is currently pressed so we can change the output char
• Returns: char the key in char form

4. Defines:

This library also includes some defines to easily get the scancodes for special keys like KEY_DOWN_EXTENDED

Not extended keys:

• KEY_TAB
• KEY_BACKSPACE
• KEY_ENTER
• KEY_CAPSLOCK
• KEY_LSHIFT
• KEY_RSHIFT
• KEY_ESC
• KEY_NUMLOCK
• KEY_SCROLLLOCK
• KEY_PAUSE

Extended keys

• KEY_RCTRL_EXTENDED

• KEY_RALT_EXTENDED

• KEY_LEFT_EXTENDED

• KEY_RIGHT_EXTENDED

• KEY_UP_EXTENDED

• KEY_DOWN_EXTENDED

• KEY_INSERT_EXTENDED

• KEY_DELETE_EXTENDED

• KEY_HOME_EXTENDED

• KEY_END_EXTENDED

• KEY_PAGE_UP_EXTENDED

• KEY_PAGE_DOWN_EXTENDED

• KEY_KP_ENTER_EXTENDED

• KEY_KP_SLASH_EXTENDED

• KEY_WINDOWS_L_EXTENDED

• KEY_WINDOWS_R_EXTENDED

• KEY_APPS_EXTENDED

• KEY_PRINT_SCREEN_EXTENDED

• KEY_BREAK_EXTENDED

• KEY_MEDIA_PLAY

• KEY_MEDIA_NEXT

• KEY_MEDIA_PREV

• KEY_MEDIA_VOLUP

• KEY_MEDIA_VOLDOWN