keybrd Library User’s Guide

keybrd is an open source library for creating custom-keyboard firmware. The resulting keyboard firmware is compatible with standard USB keyboard drivers.

This guide shows how to

• set up the Arduino development environment
• install the keybrd library
• compile and load keybrd firmware

The Arduino development environment is free and simple as possible. Its easy for novice programmers to setup and learn.

Who this guide is for

This guide is for anyone who wants to use the keybrd library to develop custom-keyboard firmware.

A reader with programming experience, but no C++ experience, would understand the tutorials well enough to modify existing keybrd sketches. An experienced C++ programmer would be able to write original sketches and classes from scratch.

The library is written in the C++ language and uses pointers, objects, classes, static class variables, composition, inheritance, and enum.

Microcontroller board requirements

The keybrd library works with Teensy and Arduino boards.

Teensy LC has 8K RAM, which is more than enough memory for any keyboard.

keybrd has been tested on the DodoHand keyboard with Teensy 2.0 and PCA9655E I/O expander using the DH_2565 sketch.

Teensy LC is preferred over the older Teensy 2.0 for it’s larger memory capacity and lower price.

Getting started with Teensy, Arduino IDE, and keybrd

The Arduino IDE is used to edit and compile sketches, and then load them on to the microcontroller.

Teensyduino is a software add-on for the Arduino IDE that allows it to compile to Teensy.

Teensy Getting Started is a good way to familiarize yourself with Teensy. Arduino Development Environment is a brief description.

The following steps create an Arduino development environment for keybrd sketches.

Install Arduino IDE and Teensyduino

Follow the install steps are modified from the Teensyduino download page

For Linux:

1. Download and extract the Arduino software. Move the extracted directory to /opt:

   $ sudo mv ~/Downloads/arduino-1.6.7 /opt/arduino-1.6.7

2. The “Linux udev rules” link is at top right of page. Save the teensy.rules file in /etc/udev/rules.d/

3. “Teensyduino Files” installer links are at top of page. Download the installer to your Downloads directory. Make the installer executable:

   $ chmod 755 teensyduino.64bit

Run the teensyduino installer and fill the form fields:

   Arduino location to install Teensyduino: /usr/local/bin/arduino-1.x.x 
   Libraries to Install: None

1. Launch Arduino IDE from /opt/arduino-1.x.x/arduino

Setup Arduino IDE for compiling keybrd firmware

From the Arduino IDE tool bar, select:

• Tools > Board > Teensy LC (or whatever board you are using)
• Tools > USB Type > Keyboard + Mouse + Joystick

optional:

• File > Preferences > Compiler warnings: All
• File > Preferences > check: Use external editor

A Sketchbook is a folder that the Arduino IDE uses to store sketches and libraries. The default location for Arduino libraries is in

~/Documents/Arduino/libraries/

Download and unpack keybrd-master.zip into your Arduino directory

todo update after testing Arduino library manager link from tutorial 7 ## Publishing

https://www.arduino.cc/en/Guide/Libraries
 > Installing Additional Arduino Libraries
 > Using the Library Manager

Down load keybrd-master.zip from the Download ZIP button.

Unpack keybrd-master.zip into your Arduino directory on your system (default location is ~/Documents/Arduino/).

keybrd library and keybrd extension libraries

todo update after testing Arduino library manager

The keybrd library contains the foundation classes for creating a keyboard firmware. For emphasis, it is sometimes referred to as the “core keybrd library”.

keybrd extension libraries contain additional classes that extend the keyboard library. keybrd extension library names are prefixed by “keybrd_“.

The Arduino IDE looks for libraries in Arduino/libraries/. For example, the DodoHand keyboard requires that the core keybrd library and the keybrd_DH extension library be installed:

• Arduino/libraries/keybrd/
• Arduino/libraries/keybrd_DH/

A keybrd extension library allows classes to be shared by multiple sketches without polluting the core keybrd library with classes that few other keyboards can use.

Compile and load keybrd sketch

If it isn’t already plugged in, plug the USB cable into the computer and controller.

CAUTION: It is possible to loose control of your keyboard when running a keybrd sketch. If the keybrd sketch has a mouse object, it is also possible to loose control of your mouse. USB keyboard protocol is capable of spewing characters and mouse commands at up to 500 per second. Take the following precautions before uploading an untested keybrd sketch to a controller:

• Save all files and close dangerous applications.
• Park the cursor in an editor opened to a test file. That way you can immediately see if the controller starts spewing characters.
• Be prepared to turn off the controller: turn off Teensy Loader’s green “Auto” button and push Teensy’s reset button if that fails, unplug Teensy USB

Compile and load workflow:

1. Open a keybrd sketch in the Arduino IDE (for example Arduino/keybrds/firmware/keybrd_single-layer/keybrd_single-layer_1221_bb/keybrd_single-layer_1221_bb.ino)
2. Prepare for loosing control of keyboard and mouse.
3. On the Arduino IDE, click the Upload button.
4. The Teensy boot loader window opens, you might need to press and release the tiny pushbutton on the Teensy circuit board.

Example keybrd sketches

Example keybrd sketches are in the keybrd_proj/keybrd/examples/ directory. Extension libraries have their example sketches similarly located.

The example sketch names use the following conventions.

keybrd_extension_feature_version.ino

where

• keybrd indicates a keybrd sketch
• extension is the extension library name e.g. DH, DualMode
• feature is distinguishing feature of keybrd sketch e.g. breadboard, LED, sound, Dvorak
• version is version number

The first two fields are mandatory, the remaining fields are optional.

Diode orientation

The physical martix rows and columns on a keyboard can be in any direction or shape. diode orientation is specified in Matrix.h

Diagram is of typical through-the-hole diode in same alignment as diode symbol. Cross bar and band depict the cathode.

Troubleshooting check list

The following is a listing of items to check when a new keybrd sketch or keyboard is having trouble.

Development-environment items to check:

• If the keyboard has an I/O expander, power cycle (replug the USB) after loading the HEX file.
• If the keybrd extension library directory name or location was changed, see section Populate Arduino/libraries with keybrd library symlinks
• If compile error: ‘KEY_A’ was not declared in this scope From the Arduino IDE tool bar, select: Tools > USB Type > Keyboard + Mouse + Joystick

Sketch items to check:

• For each row, number of keys in Row should equal number of colPort pins. In this example, row_0 has six colPort pins in ptrsColPorts, and six keys in ptrsKeys_0:

  ColPort_AVR colPortB(DDRB, PORTB, PINB, 1<<0 | 1<<1 | 1<<2 | 1<<3 );
  ColPort_AVR colPortD(DDRD, PORTD, PIND, 1<<2 | 1<<3 );
  
  ColPort* const ptrsColPorts[] = { &colPortB, &colPortD };
  const uint8_t COL_PORT_COUNT = sizeof(ptrsColPorts)/sizeof(*ptrsColPorts);
  
  const Key* const ptrsKeys_0[] = { &k_00, &k_01, &k_02, &k_03, &k_04, &k_05 };
  Row row_0(ptrsKeys_0, &rowPortF, 1<<0, ptrsColPorts, COL_PORT_COUNT);
  

• Some of the constructors take array-element-count arguments, make sure that the correct counts are passed to the constructors. Or use sizeof() like this example:

  Row* const ptrsRows[] = { &row0, &row1, &row2, &row3 };
  const uint8_t ROW_COUNT = sizeof(ptrsRows)/sizeof(*ptrsRows);
  Matrix matrix(ptrsRows, ROW_COUNT, 1);
  

• For multi-layered keyboards, the number of codes in each Key_Layered should equal the number of layers.

Hardware items to check:

• Connections
• Diode orientation
• 5 volts across power and ground
• To validate keyboard hardware, modify the simple single-layer keybrd sketch from the tutorial.

Keybrd nomenclature

scancode - Is a 16-bit integer assigned to a key position on a keyboard. The keyboard sends a scancode to the computer for every key press and release.

Layers - are key bindings provided by the keyboard firmware. The standard IBM PC keyboard has one layer. Many compact keyboards have an additional Fn layer. The Neo layout has 6 layers.

Layer code - is an integer assigned to a layer.

Layer scheme - is a system for changing layers while typing.

               A single-layer scheme does not change layers.

Layout - is a grid of keys. Key caps are often labeled to show a keyboard’s layout.

Matrix - is a collection of switches connected by rows and columns.

bounce - Keyboard switches are made of moving contacts. When the contacts close, they bounce apart one or more times before making steady contact. A debouncer removes the bounce so that a key press is sent to the computer only once.

Modifier key - is a special key on a computer keyboard that temporarily modifies the normal action of another key when pressed together. By themselves, modifier keys usually do nothing; that is, pressing any of the Shift, Alt, or Ctrl keys alone does not trigger any action from the computer.

Sketch - is the name that Arduino uses for a program

keybrd sketch - is an Arduino sketch that uses the keybrd library to define a keyboard firmware.