7.5 KiB
keybrd Library Developer's Guide
This guide if for maintaining and writing new classes for the keybrd library and its extension libraries. The most common reason for new classes are:
- Port classes for micro controller or I/O expanders
- custom layer schemes for multi-layer keyboards
- experimental features
Who this guide is for
This guide is for the maintainers and developers of the keybrd library and it's extensions. It is assumed the reader is familiar with C++ language including pointers, objects, classes, static class variables, composition, inheritance, polymorphism, and enum. Some classes use bit manipulation.
Class inheritance diagrams
Keybrd library class inheritance diagram
Matrix
Row
IOExpanderPort
_______ RowPort _______
/ | \
RowPort_AVR RowPort_MCP23018 RowPort_PCA9655E (one RowPort class for each type of IC)
_______ ColPort _______
/ | \
ColPort_AVR ColPort_MCP23018 ColPort_PCA9655E (one ColPort class for each type of IC)
_____ LED ______
/ | \
LED_AVR LED_MCP23018 LED_PCA9655E (one LED class for each type of IC)
StateLayersInterface
|
StateLayers
Key __
| \
| Key_LayeredKeysArray
|
Code
|_____________________
| \ \
| Code_LayerLock Code_LayerHold
|
|___________________________
| \ \
| Code_LayeredScScBase Code_LayeredCodeScBase
| | |
| Code_LayeredScSc Code_LayeredCodeSc
|
|__________________________________________
\ \ \ \
Code_Sc Code_Shift Code_AutoShift Code_LockLED
/ | \
Code_ScS Code_ScNS Code_ScNS_00
Dependency diagrams
single-layer dependency diagram with LEDs
matrix[1..*]
|
row[1..*]_____________________________
| \ \ \
rowPort[1] rowPin[1] colPort[1] keys[1]
| |
colPins[1..*] code[1..*]
|
LED[1]
multi-layer dependency diagram with LEDs and I/O Expander
matrix[1..*]
| stateLayers[1..*]
row[1..*]_________________________________________/__ | \
| \ \ \ / \ | \
rowPort[1] rowPin[1] colPort[1] keys[1] / code_layer[1..*] LED[0..*]
\ / \ | / /
\ / colPins[1..*] key[1..*] /
\ / | /
\ / code[1..*] /
\ / ______________________________________/
IOExpanderPort[0..*]
Class naming conventions
Class names start with upper case letter. Most derived-class names start with the base class name followed by "_" and a name e.g.
Code
|
Code_LayerLock
This convention leads to class names that convey information about the classes inheritance. Underscore delineates base class name and sub-class name. Capital letters delineate words.
Style guide
Following the style guide makes it easier for the next programmer to understand your code.
- For class names, see above section "Class naming conventions"
- For member names, use camelCase starting with lowercase letter.
- Use constants rather than macros, except for header guards.
- For constant names that could be macros, use ALL_CAPS_AND_UNDERSCORE.
- ITEM_COUNT is a constant number of items.
- itemCount is a variable number of items.
- Use header guards CLASS_NAME_H.
- Prefix pointer name with "ptr" e.g. ptrRow = &row;
- Name arrays using the plural of element name e.g. Row* const = ptrsRows { &row0, &row1 };
- Pass arrays using array notation rather than pointer notation. Use
void printArray(char[] array);
not
void printArray( char* array);
-
In constructor's initialization list, use same names for fields and constructor parameters.
-
Do not use new or malloc (making memory leaks impossible).
-
If class has any non-POD data members, do not inline constructors and destructors.
-
Document class interface in .h file, above the class declaration.
-
Code should be self-documenting. The only comments should be things that may need clarification. A simple function with a good name needs no comment.
-
Code is automatically formated before being pushed to the keybrd repository. The astyle_cpp file specifies the format:
- Allman style indentation
- indent 4 spaces
- replace tabs with spaces
- maximum code width of 100 columns
Trace of keybrd scan
Arduino does not have a debugger; so here is a list of functions in the order that they are called. Refer to it like a table of contents while reading the keybrd library.
Matrix::scan() for each row
Row::process()
Row::scan()
RowPort_*::setActivePin*() strobe row on
for each col port
ColPort_*::read() read col port
RowPort_*::setActivePin*() strobe row off
Row::getRowState() for each col port
for each connected col pin
if key is pressed
set rowState bit
Row::debounce() debounce
Row::detectEdge() detect edge
Row::pressRelease() for each key in row
if rising edge
Key_*::press() scanCode->press()
Code_*::press() Keyboard.press(scancode)
The Arduino libraries
The keybrd libraries compile on the Arduino IDE and make extensive use of the following Arduino libraries:
#include <Arduino.h>
#include <Wire.h>
#include <Keyboard.h>
#include <Mouse.h>
keybrd guide by Wolfram Volpi is licensed under a Creative Commons Attribution 4.0 International License.
Permissions beyond the scope of this license may be available at https://github.com/wolfv6/keybrd/issues/new.