91 lines
4.6 KiB
Markdown
91 lines
4.6 KiB
Markdown
Tutorial 1 - breadboard keyboard
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When you finish this tutorial you will have a working keyboard and understand how a key matrix works.
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## Why a breadboard keyboard is useful
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All the tutorial example sketches run on breadboard keyboards that have 2 to 8 keys.
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Breadboard keyboards have row-column matrices and diodes just like the big keyboards.
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A breadboard is the easiest way to learn keyboard electronics.
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Electronics are fickle, and you won't get everything right the first time.
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There is a learning curve.
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Compared to PCBs, breadboard keyboards are easier to learn on because:
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* Mistakes are easily corrected; no soldering and desoldering
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* Parts can be reused in many different configurations
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* A small keyboard is easier to trouble shoot
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Breadboard keyboards are useful for:
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* learning keyboard electronics - diodes, micro controllers, I/O expanders
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* learning the firmware development workflow
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* prototyping circuits before making a PCB
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## Breadboard keyboard starter kit
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The parts needed to build all the tutorial Breadboard Keyboards are listed in [breadboard_keyboard_supplies.ods](breadboard_keyboard_supplies.ods).
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Wire cutters (or nail clipper) is the only required tool.
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A multi-meter is useful for trouble shooting.
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## How a breadboard works
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To understand the breadboard keyboard you will need to know the internal parts of a breadboard:
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* power rail
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* terminal strip
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These are explained in [How to Use a Breadboard](https://learn.sparkfun.com/tutorials/how-to-use-a-breadboard)
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## How a keyboard matrix works
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This excellent article explains how the microcontroller, matrix, switches and diodes work together:
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[How a Key Matrix Work](http://pcbheaven.com/wikipages/How_Key_Matrices_Works/)
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## Building a basic breadboard keyboard
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The basic breadboard has 4 switches and a microcontroller.
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The key matrix has two rows and two columns.
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Breadboard power rails are repurposed as matrix rows.
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Short bare wires connect terminal strips into matrix columns.
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Switch-diode pairs connect rows to columns.
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The green rectangle on the right is the Teensy 2.0 microcontroller.
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The matrix rows and columns connect to the microcontroller via jumper wires.
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Breadboard keyboard assembly instructions:
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1. Cut leads to length.
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* tactile-switch-lead length 6 to 8 mm
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* diodes 22 to 24 mm total end-to-end length, and save the cut offs for steps 2 and 3
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2. Insert parts into the breadboard as shown in the picture.
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* diode cut offs connect terminal strips into columns
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* diodes are orient with cathode (banded end) towards the row (power strip)
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* switches connect diode to columns
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3. Insert jumper wires connecting Teensy2 to the matrix rows and columns.
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* follow pin connections table (below) and consult pinout diagram in
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[Teensy2_pinout.txt](../doc/Teensy2_pinout.txt)
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todo add a schematic
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<!-- This schematic was written by consulting the micro-controller's datasheet and using the ?? tool.
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this table might not match the sketches, replace with a schematic
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**Teensy 2.0 pin connections table**
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| Pin number | Row Column |
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|------------|-------------|
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| 21 | row_0 |
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| 20 | row_1 |
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| 0 | col_0 |
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| 1 | col_1 |
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-->
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## Compiling and loading the keyboard firmware
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Follow the [keybrd Library User's Guide](../doc/keybrd_library_user_guide.md) to set up the Arduino environment and to compile and load keybrd firmware onto the keyboard's controller.
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## Bigger breadboard keyboards
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Sometimes its useful to prototype a full keyboard matrix before designing the PCB.
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Several breadboards can be tied together into one.
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<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/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="http://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="http://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="http://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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