137 lines
5.2 KiB
Markdown
137 lines
5.2 KiB
Markdown
Tutorial 3a - multi-layer keyboard
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==================================
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When you finish this tutorial you will be able to be able to modify a multi-layer keybrd sketch to write your very own multi-layer keyboard firmware.
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Multi-layer nomenclature
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------------------------
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**[layers](http://deskthority.net/wiki/Layer)** - are key bindings provided by the keyboard firmware. For example,
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* The classic [IBM PC keyboard](http://en.wikipedia.org/wiki/IBM_PC_keyboard) has one layer.
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* Many compact keyboards have an additional [Fn layer](http://en.wikipedia.org/wiki/Fn_key).
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* The [Neo layout](http://neo-layout.org/index_en.html) has 6 layers.
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**layer id** - is an integer used to identify a layer.
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**active layer** - is the layer currently used by the keyboard.
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**layer scheme** - is a system for changing the active layer while typing (a single-layer scheme does not change layers).
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A simple multi-layer keybrd sketch
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----------------------------------
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The [keybrd_3a_multi-layer.ino](keybrd_3a_multi-layer/keybrd_3a_multi-layer.ino) sketch is for a simple two-layer keyboard.
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It will run on the basic breadboard keyboard described in [tutorial_1_breadboard_keyboard.md](tutorial_1_breadboard_keyboard.md).
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The sketch annotations explain how multi-layer keyboards work.
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The sketch uses three layer-scheme classes:
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* LayerState
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* Code_LayerHold
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* Key_LayeredKeysArray
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The internal workings of these three classes are revealed in the next section.
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Pseudo code for simple layer scheme
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-----------------------------------
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The following pseudo code is of three keybrd library classes.
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It has just enough detail to show the internal workings of layer schemes.
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**Code_Layer** objects change the active layer when pressed.
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The "layer" variable is a layer id number.
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When a Code_Layer object is pressed, it tells LayerState to update the active layer.
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```
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class Code_Layer
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{
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int layer;
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LayerState& refLayerState;
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press() { refLayerState.setActiveLayer(layer); }
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};
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```
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**LayerState** objects keep track of the active layer.
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A LayerState's activeLayer is always up to date.
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```
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class LayerState
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{
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int activeLayer;
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setActiveLayer(int layer) { activeLayer = layer; }
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getActiveLayer() { return activeLayer; }
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};
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```
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**Key_LayeredKeysArray** objects contain an array of keys, one key for each layer.
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Key_LayeredKeysArray objects use layer ids as Key_LayeredKeysArray indexes.
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When a Key_LayeredKeysArray object is pressed, it gets the active layer from LayerState, and sends the corresponding key.
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```
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class Key_LayeredKeysArray
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{
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Key** ptrsKeys; //array of Key pointers, one Key pointer per layer
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LayerState& refLayerState;
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press() { layer = refLayerState.getActiveLayer();
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ptrsKeys[layer]->press(); }
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};
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```
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Dependency diagram
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```
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+------------+
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| Code_Layer |
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+------------+
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|setActiveLayer()
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v
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+------------+
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| LayerState |
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+------------+
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^
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|getActiveLayer()
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+----------------------+
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| Key_LayeredKeysArray |
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+----------------------+
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```
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Layer-scheme classes
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--------------------
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There are several layer scheme-classes to choose from.
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You can view all the class definitions in the [keybrd library](../src/).
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Code_Layer classes include:
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* Code_LayerHold
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* Code_LayerLock
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A basic LayerState class is:
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* LayerState
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Key_Layered classes include:
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* Key_LayeredKeysArray
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* Key_LayeredScSc
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* Key_LayeredCodeSc
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The basic LayerState provided by the keybrd library is sufficient for implementing ordinary layer schemes.
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For experimental layer schemes, you would need to create a custom LayerState class, and possibly custom Code_Layer and Key_Layered classes as well.
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Single-layer Codes
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------------------
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Most Code objects only have one scancode or code.
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Example single-layer Code classes include:
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* Code_Sc
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* Code_ScS
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* Code_ScNS
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* Code_Shift
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* Code_LayerHold
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* Code_LayerLock
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Exercises
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---------
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1) Modify the keybrd_3_multi-layer.ino sketch to use two Code_LayerLock objects.
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| Layout | **0** | **1** |
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|:------:|:------:|:------:|
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| **0** | a 1 | b 2 |
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| **1** | layer0 | layer1 |
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<br>
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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 tutorial</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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