279 lines
11 KiB
Markdown
279 lines
11 KiB
Markdown
keybrd Library Developer's Guide
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================================
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This guide if for maintaining and writing new classes for the keybrd library and its extension libraries.
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The most common reason for adding new classes are:
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* I/O expander classes
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* custom layer schemes for multi-layer keyboards
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* experimental features
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Who this guide is for
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---------------------
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This guide is for the maintainers and developers of the keybrd library and it's extensions.
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It is assumed the reader is familiar with the C++ language including pointers, objects, classes, static class variables, composition, aggregation, inheritance, polymorphism, and enum.
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Row, Scanner, and Debouncer classes use bit manipulation.
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Custom Row classes
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------------------
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Row classes are central to the keybrd library.
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Row is an abstract base class that allows flexibility in designing derived Row classes:
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* Row functions can be overridden in a derived class
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* choice of Debouncers
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* choice of Scanners
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This example illustrates the custom Row classes for a fictional keybrd_Ext extension library.
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The keybrd_Ext library is for a split keyboard with a matrix on each hand and sticky keys.
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Row_Ext::keyWasPressed() overrides Row::keyWasPressed() which is used to unstick sticky keys.
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Row_Ext_uC and Row_Ext_ShiftRegisters are a custom classes composed of stock keybrd library classes.<br>
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Row_Ext_uC uses Scanner_uC to scan the primary matrix.<br>
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Row_Ext_ShiftRegisters uses Scanner_ShiftRegs74HC165 to scan the peripheral matrix.
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Class inheritance diagram
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```
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Row
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Row_Ext (override Row::keyWasPressed() )
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/ \
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Row_Ext_uC Row_Ext_ShiftRegisters (inherit Row_Ext::keyWasPressed() )
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Scanner_uC Scanner_ShiftRegs74HC165
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```
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Dependency diagram
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```
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________ Row_Ext_uC[1] ______________
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/ | \
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Scanner_uC[1] Debouncer_Samples[1] Key[1..*]
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/ |
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strobePin[1] Code[1..*]
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_________ Row_Ext_ShiftRegisters[1] ________
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/ \ \
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Scanner_ShiftRegs74HC165[1] Debouncer_Samples[1] Key[1..*]
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strobePin[1] Code[1..*]
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```
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Class inheritance diagrams
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--------------------------
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Keybrd library class inheritance diagram
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```
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________ Row ___________
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/ | \
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Row_uC Row_ShiftRegisters Row_IOE (todo to be added)
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Scanner_uC Scanner_Port Scanner_ShiftRegs74HC165
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PortIOE
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PortWrite
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PortWrite_PCA9655E (one PortWrite class for each IOE type)
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PortRead
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PortRead_PCA9655E (one PortRead class for each IOE type)
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_ LED _
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/ \
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LED_uC LED_PCA9655E
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DebouncerInterface
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Debouncer_Samples
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ScanDelay
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LayerStateInterface
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LayerState
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Key __
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| Key_LayeredKeysArray
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Code
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|_____________________
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| \ \
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| Code_LayerLock Code_LayerHold
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|___________________________
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| \ \
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| Code_LayeredScScBase Code_LayeredCodeScBase
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| Code_LayeredScSc Code_LayeredCodeSc
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|_________________________________________________________
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\ \ \ \ \
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Code_Sc Code_Shift Code_AutoShift Code_LEDLock Code_Null
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/ \
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Code_ScS Code_ScNS
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```
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Dependency diagrams
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-------------------
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Dependency diagram of example single-layer keyboard with LEDs
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```
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_ Row_uC[1..*] _
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/ | \
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Scanner_uC Debouncer Keys[1..*] __
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Code[1..*] Code_LEDLock[1..*]
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LED_PinNumber[1]
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```
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Dependency diagram of example multi-layer keyboard with layer LEDs
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```
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LayerStates[1..*]
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________ Row_uC[1..*] ___________/__ | \
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/ | \ / \ | \
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Scanner_uC[1] Debouncer[1] Keys[1..*] / Code_Layer[1..*] LED_PinNumber[0..*]
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Code[1..*]
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```
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Dependency diagram of example peripheral matrix with shift registers
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```
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Row_ShiftRegisters[1..*]
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/ \ \
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RowScanner_ShiftRegisters Debouncer Keys[1..*]
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Code[1..*]
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```
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Dependency diagram of example peripheral matrix with I/O Expander and LEDs
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```
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_____ Row_IOE[1..*] _________
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/ \ \
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__ Scanner_Port[1] __ Debouncer[1] Keys[1..*] __
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/ | \ | \
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PortWrite[1] strobePin[1] PortRead[1] Code[1..*] Code_LEDLock[1..*]
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\ / \ |
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\ / ColPins[1..*] LED[1]
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\ /
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PortIOE[0..*]
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```
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Class naming conventions
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------------------------
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Class names start with upper case letter.
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Most derived-class names start with the base class name followed by "_" and a name e.g.
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```
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Code
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Code_LayerLock
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```
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This convention leads to class names that convey information about the classes inheritance.
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Underscore delineates base class name and sub-class name. Capital letters delineate words.
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Layer-class naming conventions
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------------------------------
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Layer classes are explained in [tutorial_3a_multi-layer_keyboard.md](../tutorials/tutorial_3a_multi-layer_keyboard.md).
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*Code_Layer* class names are concatenations of "Code_", "Layer" or layer name, and persistence.
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Example persistences are:
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* "Lock" - layer remains active after the layer key is released
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* "Hold" - layer is active for as long as layer key is held down
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Example Code_Layer class names:
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* Code_LayerHold
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* Code_LayerLock
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*LayerState* class names start with "LayerState" and end with a descriptive name.
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Example LayerState class names:
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* LayerState - basic LayerState class in keybrd library
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* LayerState_DH - main LayerState for the keybrd_DH library
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* LayerState_MF - LayerState for Mouse Function sub-layers in the keybrd_DH library
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*Code_Layered* class names start with "Code_Layered" and end with a descriptive name.
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Example Code_Layered class names:
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* Code_LayeredScSc
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* Key_LayeredKeysArray
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Style guide
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-----------
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Following the style guide makes it easier for the next programmer to understand your code.
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* For class names, see above section "Class naming conventions".
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* Member names use camelCase starting with lowercase letter.
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* Use constants rather than macros, except for header guards.
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* Global const names and static const names use ALL_CAPS_WITH_UNDERSCORE.
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* Macros use ALL_CAPS_WITH_UNDERSCORE and have _MACRO suffix e.g. SAMPLE_COUNT_MACRO
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* Header guards have _H suffix e.g. #ifndef FILE_NAME_H
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* Pointer names are prefixed with "ptr" e.g. ptrRow = &row;
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* Arrays names use the plural of the element name e.g. Row* const = ptrsRows { &row0, &row1 };
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* Pass arrays using array notation rather than pointer notation:
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```
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void printArray(char[] array);
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not
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void printArray( char* array);
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```
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* In constructor's initialization list, use same names for fields and constructor parameters.
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* Do not use new or malloc (make memory leaks impossible).
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* Document class interface in .h file, above the class declaration.
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* Code should be self-documenting. A simple function with a good name needs no comment.
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* Code is automatically formatted before being pushed to the keybrd repository.
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The [astyle_cpp](astyle_cpp) file specifies the format:
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* Allman style indentation
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* indent 4 spaces
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* replace tabs with spaces
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* maximum code width of 100 columns
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<!-- http://stackoverflow.com/questions/2198241/best-practice-for-c-function-commenting -->
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Trace of keybrd scan
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--------------------
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Arduino does not have a debugger.
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So here is a list of functions in the order that they are called.
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The trace is of a one-row single-layer keybrd scan.
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Refer to it like a table of contents while reading the keybrd library.
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```
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loop() for each row
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Row::process()
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Scanner_uC::scan() strobe row on
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for each readPin
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set readState bit
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strobe row off
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Debouncer_Samples::debounce() debounce
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Row::send() for each key in row
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if falling edge
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Key_*::release() scanCode->release()
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Code_*::release() Keyboard.release(scancode)
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if rising edge
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Key_*::press() scanCode->press()
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Code_*::press() Keyboard.press(scancode)
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scanDelay.delay();
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```
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The Arduino libraries
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---------------------
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The keybrd libraries compile on the Arduino IDE and make extensive use of the following [Arduino libraries](https://www.arduino.cc/en/Reference/Libraries):
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#include <Arduino.h>
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#include <Wire.h>
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#include <Keyboard.h>
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#include <Mouse.h>
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<a rel="license" href="https://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://licensebuttons.net/l/by/4.0/88x31.png" /></a><br /><span xmlns:dct="http://purl.org/dc/terms/" property="dct:title">keybrd guide</span> by <a xmlns:cc="https://creativecommons.org/ns" href="https://github.com/wolfv6/keybrd" property="cc:attributionName" rel="cc:attributionURL">Wolfram Volpi</a> is licensed under a <a rel="license" href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>.<br />Permissions beyond the scope of this license may be available at <a xmlns:cc="https://creativecommons.org/ns" href="https://github.com/wolfv6/keybrd/issues/new" rel="cc:morePermissions">https://github.com/wolfv6/keybrd/issues/new</a>.
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