87 lines
4.0 KiB
Markdown
87 lines
4.0 KiB
Markdown
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Tutorial 0 - breadboard keyboard
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When you finish this tutorial you will have a working keyboard and understand how its key matrix works.
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[breadboard keyboard with 2 rows and 2 columns]
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(images/breadboard_keyboard_2x2_labeled.jpg "2x2 breadboard keyboard")
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## Why a breadboard keyboard is useful
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A breadboard is the easiest way to learn keyboard electronics.
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Electronics are fickle, you won't get everything right the first time, there is a learning curve.
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Breadboards make the learning electronics faster and fun.
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Breadboard keyboards have row-column matrices and diodes just like the big keyboards.
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Compared to full size keyboards on PCBs, breadboard keyboards are easier to work with because:
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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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* Mistakes are easily corrected because no desoldering
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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 process
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* prototyping circuits before making a PCB
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* testing firmware concepts before building the keyboard hardware
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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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* terminal strip
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* power rail
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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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## Breadboard keyboard starter kit
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The parts needed to build all the Breadboard Keyboards in the keybrd tutorials are listed in [breadboard_keyboard_supplies.ods](breadboard_keyboard_supplies.ods).
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Wire cutters (or nail clippers) is the only required tool.
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A multi-meter is useful for trouble shooting.
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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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[breadboard keyboard with 2 rows and 2 columns of keys]
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(images/breadboard_keyboard_2x2_labeled.jpg "2x2 breadboard keyboard")
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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 switches into matrix columns.
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Diodes connect switches to rows.
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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, they will be used in steps 2 and 3
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2. Insert parts into the breadboard as shown in the picture.
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* orient the switches such that the leads are on separate terminal strips
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* orient diodes with cathode (banded end) towards the row (power strip)
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* use the diode cut offs to connect switches into 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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[Connecting Teensy 2.0 to a Keyboard](connecting_teensy2_to_keyboard.md)
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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 | todo this table might not match the sketches
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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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## Compiling and loading the keyboard firmware
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Follow the [keybrd Library User's Guide](todo /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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## How a keyboard matrix works
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Now that you have built your first breadboard keyboard, you can dig in and learn how it actually 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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## Bigger breadboard keyboards
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Sometimes its useful to prototype the full keyboard matrix before designing the PCB.
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Several breadboards can be tied together into one.
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[big breadboard keyboard](breadboard_big.jpg "breadboard_big.jpg")
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