keybrd/tutorials/tutorial_3a_multi-layer_keyboard.md

Tutorial 3a - multi-layer keyboard

After reading this tutorial you will be able to be able to modify a multi-layer keybrd sketch to suite your own multi-layer keyboard design.

Multi-layer nomenclature

layers are key bindings provided by the keyboard firmware. For example,

• The full-size 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 used to identify a layer.

active layer - is the layer currently used by the keyboard.

layer scheme - is a system for changing layers while typing (a single-layer scheme does not change layers).

A simple multi-layer keybrd sketch

This annotated sketch demonstrates the multi-layer feature: keybrd_3_multi-layer_annotated.ino

Layer scheme classes

The walkthrough example covered the most basic classes. This section takes a general view of layer scheme classes. You can view all the class definitions in the keybrd library.

StateLayer

StateLayer object has an active layer. StateLayer keeps its active layer up to date. There is only one StateLayer class:

• StateLayer

Layer

Layer objects control the active layer. For example, there could be one layer key for each layer. When a Layer object is pressed, it tells StateLayer to change the active layer. Example Layer classes include:

• Code_LayerHold
• Code_LayerLock

Multi-layered

Layered objects contain one scancode for each layer. When a Layered object is pressed, it gets the active layer from StateLayer, and then sends the scancode of the active layer. Example Layered classes include:

• Code_LayeredScSc
• Code_LayeredCodeSc
• Code_LayeredCodeCode
• Key_LayeredKeysArray

Single-layer Codes

Most Code objects only have one scancode or one layer code. They do are not affected by the active layer. Example single-layer Code classes include:

• Code_Sc
• Code_ScS
• Code_ScNS
• Code_Shift
• Code_LayerHold
• Code_LayerLock

(Future version of keybrd library may change all Code classes to Key classes.)

Exercises

1. Modify the keybrd_3_multi-layer_annotated.ino sketch to use two Code_LayerLock objects.

Layout	0	1
0	a 1	b 2
1	layer0	layer1